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If you want to build a 100,000-cubit-trapped ion machine, you're going to have to invent a 100,000 laser optical miracle.

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Yeah.

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All right?

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But if you want a million superconducting qubits, you're going to have to build a warehouse-sized priostat.

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But if you want a million spin qubits, you just put it on a standard 300-millimeter silicon wafer.

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You run it through the exact same photolithography machines at TSMC.

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asml intel scaling is the key yeah and scaling is the future hello internet this is your captain speaking lester nare joined as always by my co-host and our resident phd krishna chowdhury this is part two

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of our two-part deep dive on quantum computing.

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We are covering the recent Nature Cover Story, Volume 655, Issue 8125, released on July 30th, 2026, and featuring our resident PhD, Krishna, as one of the co-authors.

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For those of you joining us from Part 1 in the last episode, we did a deep dive into

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Now we get to the beef.

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We talked about what is it?

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Why would we want to build quantum computer?

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In this episode, we're going to take a deep dive into how to actually make one.

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And Krishna is going to make the case that there is only one way.

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Make it silicon.

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As a brief note, the opinions expressed in this episode are those of us personally here as the hosts and do not represent the views or opinions or positions of any entities that may be mentioned previously.

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throughout this episode as we talked about in the last episode.

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This is a burgeoning trillion dollar industry.

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We are talking about this from our personal viewpoints and the opinions expressed in this episode are our own.

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As always, we are going to talk about the science from the ground up today because this is from First Principles.

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It's change only coobits, they feel so right.

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Scalable quantum shining in the night.

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It's change only coobits.

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No noise scene.

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Exchange only cool bits.

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Do it with ease.

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Scalable bottle up.

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Longtime listeners of this podcast might recognize that the intro music today is different from our usual music.

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And that's because today is a very special episode.

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We're going to repeat the song at the very end of the episode in the credits, and you can take a listen afterwards, and hopefully you'll understand the lyrics.

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The reason why this is a special episode is because, you know, we've covered probably a hundred scientific papers on this podcast over the past year.

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a scientific paper where I am co-author.

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I'm one of 250.

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It's a very large list of co-authors because it took a lot of human power, a lot of resources to do what we've done.

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But it's a special day.

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It's a special episode.

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I'm holding it right here.

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Nature's Volume 655, Issue 8125.

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Quantum

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Silicon.

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All right.

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Look at it.

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Look at it.

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Shout out to John Carpenter for the visuals on the cover.

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So this is a paper out of HRL Labs in Malibu, which was my former workplace.

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And it was recently announced that IBM has acquired the place.

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So hopefully...

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By the time this episode ends, it'll give you a little bit of context about why that is a very interesting move.

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Okay?

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Now, this is not the first nature cover story to have quantum computing or adjacent things.

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Okay?

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We've got several.

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Mighty Atoms is a trapped ion story.

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Quantum supremacy, that's the Google one about quantum supremacy.

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There's the weird, like, holographic wormhole thing.

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I don't know if you remember, but, like...

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Some people did some quantum experiment on a computer that suggested that they've finally realized the Einstein-Rosen bridge and like wormholes exist.

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We tapped into it.

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And it's like, no, you know, that's not what happened.

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But in any case, the current cover that I'm holding here is in a long line.

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It's kind of the debut of a type of MVP, you know, that they say in VC circles.

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Minimum viable product.

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That's right.

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This is an MVP for a type of quantum computer that I think will be the future quantum computer.

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Okay.

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Why?

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Well, because it's in the name right here.

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Quantum Silicon.

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It's made out of silicon, which means that it can be made using the same machines and the same infrastructure that makes all of the classical computers that are in my phone, that are in this laptop, and in everything that we know and love.

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whenever we have some new technology or some new paradigm, the question becomes, okay, you can prove it in the lab, but then how do you scale it in a production environment to actually make it viable for business use cases?

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Graphing.

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And to that point, you know, there's a, there's a,

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gap between the theoretical application and the production scale application.

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That's right.

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And so part of where I think you're saying we are is there are different approaches to how can we make this work at scale.

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Yes.

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And you're going to make the argument today that this debut is the way to make it work at scale because there's been promise around quantum computers for some time and it's

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we will have a fundamental understanding of why this is the way forward.

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Exactly, yeah.

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And to be clear, you've already given the disclaimer, but I'll just say it again.

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This is not a normal episode in that we will be covering a lot of cool science.

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I mean, it is kind of a normal episode because we will be covering a lot of cool science and science history from First Principles, but it will be unlike other episodes.

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um because it will not be unbiased science journalism now i don't know if the other episodes were unbiased science journalism to to be prefer perfectly honest but um here i definitely have an agenda and the agenda will become pretty obvious as the episode goes on but i want to make it explicitly clear here so there's no confusion and debate and people are in the comments being like you're biased you're drinking the kool-aid yeah it's my kool-aid

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I made it.

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And I'm drinking it.

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Yeah.

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Purple.

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Red.

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Exactly.

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So this will be an opinionated episode and the opinions are entirely our own.

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I do want to also just note for those who are audio listeners, as we were setting up the production for this episode, this episode has the most visual overlays of any episode we ever, we've ever done.

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Yeah.

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It's quite, there's a lot of complex ideas that are only best expressed by the

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by looking at it visually.

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And so to the extent that you can catch it on YouTube or on Spotify, where we'll have the full video available, I do encourage folks after maybe a first listen via audio to do so because it is going to be very visually heavy.

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Yeah, yeah, yeah.

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And it's going to be a lot of fun.

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I mean, I had a lot of fun planning out the notes for this episode.

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This is going to be fantastic.

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I mean, it's a paper that I'm on.

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And we're actually going to go into a deep dive, not just about silicon quantum computers, which is the subject of the paper, but quantum computing hardware in general.

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And I want to answer the question, how do you make a good computer?

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quantum computer and what does that word good mean in this context right um there's going to be a shallow deep dive on other quantum technologies you know we've got superconducting circuits trapped ions neutral atoms and then i'm going to make the case for why this technology quantum is going to win there's the agenda yes that's that's the agenda the agenda yeah and um i used to work at hrl which is where the paper comes from but now i work at a company called dirac

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Great name, by the way.

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And Dirac also works on spin quantum computers in silicon.

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So it's always been spins for me.

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That's fair.

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There's these other options, but you've been in the spin universe in terms of this is the way.

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Yeah, this is the way.

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This is the way.

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Because it's still early in this race to make the first quantum computer.

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Other players might want you to not think that, right?

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Quantum supremacy on the cover of Nature.

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They did it.

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Yeah.

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Well, okay, you simulated a probability distribution that is designed for a quantum computer to simulate because it was a quantum probability distribution.

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Okay, all right, cool.

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There are different strategies.

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We've got superconducting circuits, as I said, trapped ions, neutral atoms.

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And for a very long time, actually, those technologies have been members of the Premier League system.

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of quantum the premier league of quantum yeah yeah get in yeah yeah yeah and silicon has been like the underdog like what's the what's the championship the champ under the premier league the championship okay so what's under championship oh uh uh we'll just say third division yeah yeah yeah i would say silicon has been like third division it hasn't even been in the championship yeah i mean the premier league the championship and then there's one more and everyone's gonna hate me for not remembering yeah we've been we've been like wrexham you know you know the ryan reynolds

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Yeah, it's been like Manchester United, Arsenal, and Chelsea.

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That's been superconducting circuits, trapped ions, and neutral atoms.

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And then Silicon has kind of been like Wrexham.

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Okay.

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No, that's really good.

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Who's basically every season...

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Yeah.

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Gone up.

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It's gone up from being in non-league play, which is like below six.

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Yeah.

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Yeah.

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And to really demonstrate that worldview, let me share a story with you.

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Okay.

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Okay.

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So I'm going to bring you back to March meeting, 2026.

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We're going to go back to this event a lot, but the American Physical Society, APS, has a March meeting every year.

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Oh, I remember this.

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And this 2026, I got to present on some of the work that actually contributed to my getting on this paper.

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Yeah.

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So I was giving a talk on behalf of HRL.

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There I am.

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And I'm actually wearing the FFP pod.

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That was, I think, the first sweater that we had made to try out whether merch would work.

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And so I had the platonic solids and I was wearing it.

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I was representing.

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This was a meeting where this technology had its big debut to the outside world.

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All of the stuff that you see on this paper, for the first time, the outside world got to see it at this meeting.

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Okay.

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there's a juicy little backstory that we'll get into, but that night.

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Okay.

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So after that, after that presentation, I'm feeling good.

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A lot of people said it was a great presentation.

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You know, I'm having, I'm, I'm, I'm riding high.

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Right.

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So I snag an invite to the Alison Bob party bar in Denver.

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Alison Bob is a quantum computing company out of Europe.

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Yes.

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And they like, you know,

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I guess rented out a bar and then you, you got to get, get like mail in invites.

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And then one of my friends, um, from PhD days, Elliot boar, shout out to Elliot.

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Shout out Elliot.

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He got me a fan, long time listener.

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Yeah.

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And he, he got me the, he forwarded me the email invite.

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So then I got to go.

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They had some great drinks at the bar, by the way.

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And they were all quantum themed.

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So I took a photo of the cocktail menu.

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You got mango collider, strawberry field theory, Bellini barrier, like a tunneling barrier, uncertainty principle.

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That was kind of lazy.

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Dark matter, mocking Bellini.

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I didn't understand that.

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If someone has an idea of why that's quantum related.

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Anyways, I wanted to be a good guest.

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Right.

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You got to be a good guest.

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So you got to try everything.

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Yes.

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They put a lot of thought into the cocktail menu.

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So I got to try every single cocktail.

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I'm not going to disrespect as a guest.

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I try every single cocktail.

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I'm feeling good.

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Just had a great talk.

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Been getting compliments all day.

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And this is a nice like day ender.

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Me and my friends, we see the traditional group of Europeans outside the bar in the smoking section.

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Yes.

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This is true for any international physics, even just science conference in general.

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There's going to be a gaggle of Europeans outside the bar just chain smoking.

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Okay?

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And I wanted to enjoy some fresh air in Denver.

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Yes.

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We head over there to socialize.

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Yes, with our international collaborators.

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Yes, exactly.

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For our colleagues to get some fresh air straight into my lungs.

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And again, I've had a couple of beers.

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So I'm away from home.

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So some fresh air in my lungs is not – it's permissible.

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And I had a great talk.

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You know, whatever.

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We joined them.

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We get to socializing, find out that they're all from Munich, Germany.

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Yes.

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Okay.

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The conversation turns to work.

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Okay.

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And one of the scientists, yeah, one of the scientists asked me, you know, what do you work on?

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And I said, automation in spin qubits.

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Yeah.

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And they go, spin qubits?

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What's that?

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And it's as if I had said, like, qubits made out of cheese.

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Like, they just had no idea.

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They'd never even heard of spin qubits.

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I'm like, okay.

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I try to keep the conversation going.

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I return the courtesy.

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I'm like, all right, what do you work on?

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They say neutral atoms.

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And I say, oh, yeah, okay.

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Okay.

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And then the killer, this German person, they say, yeah, see, you know about my technology, but I don't know about yours.

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So maybe that says something.

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There is a reason, yeah?

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And everyone starts laughing and I'm like an idiot.

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You know, I can't.

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I'm caught off guard so much that I'm just laughing at myself.

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I was so ill prepared for this ambush.

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For the quip.

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00:13:57.848 --> 00:13:58.588
Yeah, for the quip.

235
00:13:58.688 --> 00:14:00.330
I thought we were having a good time.

236
00:14:00.350 --> 00:14:01.211
It was a cool quip.

237
00:14:01.451 --> 00:14:01.691
Yeah.

238
00:14:02.091 --> 00:14:03.852
Like you could, you could have just been nice.

239
00:14:04.372 --> 00:14:04.532
Right.

240
00:14:04.572 --> 00:14:13.295
Like if somebody, if somebody comes up to me at APS and they're like, I work at Microsoft on topological qubits, I'm not going to be like, what topological qubits?

241
00:14:13.775 --> 00:14:13.935
Right.

242
00:14:13.955 --> 00:14:17.816
I'm not going to say, I'm not going to say, are the topological qubits in the room with us?

243
00:14:17.916 --> 00:14:18.097
Right.

244
00:14:18.137 --> 00:14:19.437
Like, I mean, it's true.

245
00:14:19.517 --> 00:14:22.138
I could think it, but I'm not going to say it.

246
00:14:22.238 --> 00:14:24.979
And the background around that joke is Microsoft has...

247
00:14:25.599 --> 00:14:27.499
These things that they call topological qubits.

248
00:14:27.619 --> 00:14:31.240
Not everyone in the industry is convinced that it's even a qubit.

249
00:14:31.300 --> 00:14:34.101
It's a two-level system, but they might have something.

250
00:14:34.141 --> 00:14:35.121
They just haven't shown it yet.

251
00:14:35.181 --> 00:14:40.523
And there's a running joke that the only people who believe that Microsoft has a qubit is Microsoft.

252
00:14:40.783 --> 00:14:41.663
Okay, so that's a joke.

253
00:14:41.683 --> 00:14:44.463
But if I'm at a bar, I'm not going to say that.

254
00:14:44.523 --> 00:14:44.743
Yes.

255
00:14:44.984 --> 00:14:45.204
Right?

256
00:14:45.304 --> 00:14:47.044
But you also don't have a German sense of humor.

257
00:14:47.224 --> 00:14:48.044
Yeah, yeah, yeah.

258
00:14:48.084 --> 00:14:49.905
And these Germans, right?

259
00:14:50.045 --> 00:14:54.506
It's also hard to have a comeback to, I haven't even heard of that.

260
00:14:54.606 --> 00:14:55.166
Yeah, yeah, yeah.

261
00:14:55.706 --> 00:14:55.946
Right?

262
00:14:56.006 --> 00:14:56.246
Like...

263
00:14:57.107 --> 00:14:58.147
He doesn't even go here.

264
00:14:58.227 --> 00:14:58.588
Yeah, yeah.

265
00:14:58.648 --> 00:15:09.834
It's like, remember in Pirates of the Caribbean when Jack Sparrow gets captured by the British dude and the British guy's like, you must be the worst pirate I have ever heard of.

266
00:15:10.194 --> 00:15:12.395
And then Jack Sparrow goes, but you have heard of him.

267
00:15:14.600 --> 00:15:40.474
do that that's good never even heard of me yeah right right right right and so what do you and when so what do you there there's no clap back there's no like possibility even even in the moment i couldn't think of anything so i go back to my hotel room and i don't know if you do this but whenever like things like that happen you take a long shower oh yeah and you just start like fantasizing yeah and rehearsing like all the different ways that could have gone down like like dr strange yes

268
00:15:40.974 --> 00:15:42.095
All the multiverses.

269
00:15:42.155 --> 00:15:43.016
All the many worlds.

270
00:15:43.056 --> 00:15:43.897
Yeah, all the many worlds.

271
00:15:43.917 --> 00:15:44.798
That we don't exist in.

272
00:15:44.818 --> 00:15:45.499
Yeah, yeah, yeah.

273
00:15:45.599 --> 00:15:47.741
Of like, where I'm like, I look like Shah Rukh Khan.

274
00:15:48.181 --> 00:15:51.564
And I'm like, I'm just, you know, there's a comeback after comeback.

275
00:15:52.465 --> 00:15:55.108
I started thinking about like, stuff I could have said.

276
00:15:55.885 --> 00:15:59.227
You know, one of them could have been like, you know, OK, so you haven't heard me.

277
00:15:59.607 --> 00:16:00.367
You haven't heard of me.

278
00:16:00.848 --> 00:16:02.969
Maybe I know more than you.

279
00:16:02.989 --> 00:16:05.050
That was the that was the like the layup.

280
00:16:05.090 --> 00:16:05.350
Yeah.

281
00:16:05.590 --> 00:16:08.372
Like maybe like maybe read the literature.

282
00:16:08.792 --> 00:16:10.293
Oh, I'm sorry that you're not well versed.

283
00:16:10.333 --> 00:16:10.553
Yeah.

284
00:16:10.613 --> 00:16:10.853
Yeah.

285
00:16:11.093 --> 00:16:11.493
Yeah.

286
00:16:11.513 --> 00:16:12.354
Yeah, exactly.

287
00:16:12.394 --> 00:16:17.637
It's like it's like I thought like not knowing stopped being cool in like middle school.

288
00:16:17.657 --> 00:16:21.379
Remember those guys would just like love to not know like, shit, I don't know.

289
00:16:21.839 --> 00:16:25.541
Like, how is that something that we're still doing at APS March meeting?

290
00:16:26.510 --> 00:16:28.932
Sorry, I'm getting a little... No, it's okay.

291
00:16:29.092 --> 00:16:31.473
You know, the PTSD is palpable.

292
00:16:31.593 --> 00:16:33.835
Bro, it's ridiculous.

293
00:16:34.075 --> 00:16:34.575
But guess what?

294
00:16:34.595 --> 00:16:35.576
Who's on the cover of Nature?

295
00:16:35.856 --> 00:16:36.336
That's right.

296
00:16:37.437 --> 00:16:38.477
Do you like apples?

297
00:16:38.497 --> 00:16:40.098
Well, I got a Nature cover.

298
00:16:40.359 --> 00:16:41.880
How about Dem apples?

299
00:16:42.100 --> 00:16:43.100
I guess you should have known.

300
00:16:43.320 --> 00:16:43.561
Right?

301
00:16:43.841 --> 00:16:44.061
Yeah.

302
00:16:44.401 --> 00:16:44.721
I mean...

303
00:16:46.151 --> 00:16:52.873
So what I would like the audience to do right now is try to figure out just using neutral atoms, right?

304
00:16:53.093 --> 00:16:54.933
Like something I could have said.

305
00:16:55.393 --> 00:16:58.234
It can be about Germany and how they lost the war.

306
00:16:58.674 --> 00:16:59.854
It can be just anything.

307
00:16:59.894 --> 00:17:05.336
I want to read these comments because I don't pay attention to my mental health, and this is going to be my therapy to get over this.

308
00:17:05.416 --> 00:17:05.716
Okay?

309
00:17:05.736 --> 00:17:10.937
So in the comments, drop something about neutrality, neutral atoms, Switzerland, anything.

310
00:17:11.337 --> 00:17:12.357
I want to read all about it.

311
00:17:12.657 --> 00:17:15.798
You don't have to know about the physics, although later I'll get into the physics and maybe—

312
00:17:16.178 --> 00:17:17.160
You can work that in.

313
00:17:17.501 --> 00:17:23.594
But this is an ask for the audience for help in my PTSD recovery.

314
00:17:23.895 --> 00:17:27.502
And I think part of what you're sort of setting up here is...

315
00:17:29.418 --> 00:17:40.146
The methodology that you all were working on was below zero, even in just like awareness, the idea that it was possible.

316
00:17:40.206 --> 00:17:40.466
Yeah.

317
00:17:40.606 --> 00:17:43.588
You were not even in the boat that was in the race.

318
00:17:43.748 --> 00:17:44.509
Yeah.

319
00:17:44.709 --> 00:17:46.710
There's really like people say there's three.

320
00:17:46.811 --> 00:17:50.133
Maybe photonics can be the fourth one, but for a long time, it's just been those four.

321
00:17:50.573 --> 00:17:52.476
And those are the four that are taken seriously.

322
00:17:52.556 --> 00:17:59.323
Now, the serious practitioners in those four know what a dark horse quantum silicon is, okay?

323
00:17:59.664 --> 00:18:01.165
And what silicon qubits can do.

324
00:18:01.586 --> 00:18:10.676
I think this person was just like maybe an early grad student, you know, just starting out, trying to be funny in front of his lab, whatever, you know?

325
00:18:10.756 --> 00:18:11.397
Yeah, yeah.

326
00:18:11.959 --> 00:18:12.299
Whatever.

327
00:18:12.420 --> 00:18:13.180
I'm over it.

328
00:18:13.240 --> 00:18:13.681
No, I'm not.

329
00:18:13.741 --> 00:18:14.561
But, you know, it's...

330
00:18:15.582 --> 00:18:17.764
I've been thinking about that event ever since.

331
00:18:18.265 --> 00:18:22.909
Because I think it sort of reflects the idea of the state of play in the race.

332
00:18:23.109 --> 00:18:23.369
Yeah.

333
00:18:24.050 --> 00:18:25.611
Or what is the best approach.

334
00:18:25.871 --> 00:18:25.991
Yeah.

335
00:18:26.011 --> 00:18:26.111
Yeah.

336
00:18:27.052 --> 00:18:30.115
And that person clearly thinks it's neutral Adams, right?

337
00:18:30.475 --> 00:18:35.040
It's been in the back of my mind ever since that day because I knew that I'd be doing this episode.

338
00:18:35.120 --> 00:18:37.582
I knew that the work was going to come out.

339
00:18:38.043 --> 00:18:41.126
I knew that it was big enough that it was definitely going to get into one of the top journals.

340
00:18:41.246 --> 00:18:46.431
It's always a crapshoot to get on the cover, but there was a chance that we would be on the cover.

341
00:18:46.471 --> 00:18:49.574
And I knew that at some point I would cover it on the podcast.

342
00:18:49.594 --> 00:18:50.675
And I was just trying to think like...

343
00:18:51.275 --> 00:18:52.896
How the clapback episode.

344
00:18:53.016 --> 00:18:53.857
Yes.

345
00:18:54.077 --> 00:18:57.859
Like, how was I going to structure this in that one hour long shower?

346
00:18:58.079 --> 00:19:02.582
You know, I was thinking about all the different ways that I could clap back.

347
00:19:03.103 --> 00:19:06.084
And so this is that clapback.

348
00:19:06.125 --> 00:19:06.345
Yeah.

349
00:19:06.525 --> 00:19:07.826
This episode is that clapback.

350
00:19:07.846 --> 00:19:09.507
You know, I think that story, right.

351
00:19:09.527 --> 00:19:11.228
It gives a good sense of like where the field was.

352
00:19:12.264 --> 00:19:13.765
And what people thought about spins.

353
00:19:15.485 --> 00:19:19.567
But now I get to talk about it on my show.

354
00:19:19.627 --> 00:19:19.827
Yes.

355
00:19:20.227 --> 00:19:22.368
So with that, let's actually get started.

356
00:19:24.168 --> 00:19:26.289
I'm going to repeat the agenda for the rest of the episode.

357
00:19:26.869 --> 00:19:27.870
The agenda is the following.

358
00:19:28.110 --> 00:19:31.351
First, we're going to talk about what makes a good quantum computer.

359
00:19:31.731 --> 00:19:36.173
What are the criteria that a good quantum computer needs to satisfy?

360
00:19:36.920 --> 00:19:45.362
Next, we'll go over the other computing technologies, superconducting circuits, trapped ions, and, of course, neutral atoms from our German boy.

361
00:19:45.962 --> 00:19:50.144
And then finally, we'll get into quantum silicon, this paper that's out in nature.

362
00:19:50.404 --> 00:19:54.605
We'll go over the history of the field briefly and where the recent paper fits in.

363
00:19:55.645 --> 00:20:05.069
And we're going to make sense of this cover photo because this cover photo has a lot of really cool tidbits that I think will be cool to understand, like why certain parts are highlighted, things like that.

364
00:20:05.089 --> 00:20:05.670
It's quite nice.

365
00:20:05.830 --> 00:20:06.950
Yeah.

366
00:20:07.090 --> 00:20:09.071
If you notice, there's three parts highlighted here.

367
00:20:09.111 --> 00:20:11.012
There's this square up here.

368
00:20:11.312 --> 00:20:13.153
Then there's this like sort of...

369
00:20:14.224 --> 00:20:15.706
Half pipe, a quarter pipe.

370
00:20:15.746 --> 00:20:16.727
Quarter pipe looking thing.

371
00:20:16.747 --> 00:20:17.488
It's like a ribbon.

372
00:20:17.508 --> 00:20:17.828
Yeah.

373
00:20:18.068 --> 00:20:21.132
And then there's this tiny little square down here.

374
00:20:21.472 --> 00:20:24.936
So those are the three that are the big three that came out of this paper.

375
00:20:24.976 --> 00:20:26.177
And we're going to talk about all those.

376
00:20:27.078 --> 00:20:30.482
And what this paper means for the future of quantum computing in general.

377
00:20:30.502 --> 00:20:30.742
Yeah.

378
00:20:30.902 --> 00:20:32.263
So that's going to be the episode.

379
00:20:32.964 --> 00:20:34.565
And before that, let's do some housekeeping.

380
00:20:34.605 --> 00:20:36.306
We'll do some brief housekeeping.

381
00:20:36.346 --> 00:20:38.708
For those joining us for the first time, welcome.

382
00:20:39.088 --> 00:20:41.950
This is the best science show on the planet.

383
00:20:42.350 --> 00:20:54.258
For those who really want to understand the fundamentals of the latest breaking frontier science research, as always, the best way that you can support the pod is a like, a share, a comment.

384
00:20:54.579 --> 00:20:59.162
Put it in the group chat, five star if you're listening on any of the podcast networks.

385
00:20:59.562 --> 00:21:02.164
Really helps us get this show to more people.

386
00:21:02.224 --> 00:21:07.087
We are available in video on Spotify and YouTube, as we mentioned.

387
00:21:07.487 --> 00:21:13.550
Again, we are waiting for Spotify creators to do video distribution to Apple Podcasts.

388
00:21:13.570 --> 00:21:16.032
For those commenting on it, we have not forgotten.

389
00:21:16.512 --> 00:21:20.514
It is just in process by late 2026.

390
00:21:20.914 --> 00:21:25.235
And so we should see that hopefully before our Christmastime wishes get done.

391
00:21:25.255 --> 00:21:26.596
I'll try to keep this tight today.

392
00:21:26.616 --> 00:21:32.338
So a couple of quick other points of order for our winners of our one-year

393
00:21:33.058 --> 00:21:34.900
merch anniversary episode.

394
00:21:34.960 --> 00:21:38.443
We have just sent out those emails to you.

395
00:21:38.883 --> 00:21:42.707
And so you should have a link to claim the merch from our shop.

396
00:21:42.747 --> 00:21:48.552
We appreciate, again, those of you who responded and have been here with us for some time.

397
00:21:49.152 --> 00:21:56.559
And it was really incredible to hear a little bit of feedback, again, for what folks want to see from us in year two.

398
00:21:57.339 --> 00:21:58.020
We also

399
00:21:58.481 --> 00:22:01.006
have just put out our transfer portal.

400
00:22:01.347 --> 00:22:06.016
Again, it is the transfer season in science, just like it is in sports.

401
00:22:06.597 --> 00:22:10.605
And after our last episode, many of you said you'd be interested in seeing this evolve.

402
00:22:10.864 --> 00:22:15.785
So we've put out a first test at ffppod.com backslash transfers.

403
00:22:16.105 --> 00:22:27.128
You can see some of the latest high-level transfers happening all across the world into the U.S., out of the U.S., and where are the best and brightest going to build the future of science.

404
00:22:27.148 --> 00:22:33.849
If you would like to donate, you can also donate at the website ffppod.com backslash donate.

405
00:22:41.151 --> 00:22:52.074
And so with that, we are going to get back to the quantum, no quantum mania, bad Marvel movie, but to this idea, spin cubits.

406
00:22:52.574 --> 00:22:53.074
That's right.

407
00:22:53.614 --> 00:23:01.997
And before we get started dragging all the neutral atoms people and everyone else through the mud, which I promise we are going to get to.

408
00:23:02.537 --> 00:23:03.177
Don't you worry.

409
00:23:04.277 --> 00:23:06.319
We do need to establish some ground rules, right?

410
00:23:06.399 --> 00:23:19.807
Because if we're going to evaluate whether a quantum computing architecture is a legitimate computational platform that can scale, or if it's just a multi-million dollar physics art installation, we need a rigorous scorecard.

411
00:23:20.368 --> 00:23:20.668
All right?

412
00:23:21.008 --> 00:23:21.789
We need a scorecard.

413
00:23:21.829 --> 00:23:23.069
So first, let's kill the hype.

414
00:23:23.710 --> 00:23:30.074
And I'm going to just briefly review last episode to catch everyone up on what is a quantum computer and what is it not.

415
00:23:30.174 --> 00:23:31.595
A quantum computer is not...

416
00:23:32.332 --> 00:23:38.316
A machine that tries every single answer at the same time because a qubit is a zero and a one simultaneously.

417
00:23:39.437 --> 00:23:39.577
No.

418
00:23:40.077 --> 00:23:40.338
Okay.

419
00:23:40.658 --> 00:23:43.200
A quantum computer is a giant interference machine.

420
00:23:43.540 --> 00:24:00.632
There's more details in the last podcast, but effectively the entire game with quantum algorithms, whether it's Shor's algorithm to make Bitcoin go to zero or Grover's or simulating some electronic ground state of some new compound that you've made, you're applying unitary transformations.

421
00:24:00.652 --> 00:24:00.852
Okay.

422
00:24:01.543 --> 00:24:08.345
So that the wrong answers undergo destructive interference and the right answers undergo constructive interference.

423
00:24:08.745 --> 00:24:15.247
And that interference effect is going to tell you, one way or the other, what the answer is.

424
00:24:15.727 --> 00:24:18.467
And a good quantum computer is something that can do all of this.

425
00:24:18.607 --> 00:24:23.229
It can store quantum information, one, and then it can manipulate quantum information.

426
00:24:23.749 --> 00:24:26.209
It can read it out so I can get an answer out.

427
00:24:26.790 --> 00:24:28.410
And it can be very large.

428
00:24:28.942 --> 00:24:32.803
It's something that is small now, but might be easy to scale up.

429
00:24:33.863 --> 00:24:34.083
Okay?

430
00:24:34.363 --> 00:24:37.944
The fundamental unit of a quantum computer is a qubit.

431
00:24:38.644 --> 00:24:41.984
We're used to classical bits, which is just a bit.

432
00:24:42.024 --> 00:24:43.505
That can be either a 0 or a 1.

433
00:24:43.885 --> 00:24:45.085
Usually it's the transistor.

434
00:24:46.685 --> 00:24:48.546
It'll either let current through or it won't.

435
00:24:48.946 --> 00:24:54.607
A qubit, you can imagine, is in a superposition of 0 and 1.

436
00:24:54.887 --> 00:24:56.067
And really, mathematically...

437
00:24:56.687 --> 00:25:02.772
what you can do is say a bit is basically whether I'm on the north pole or the south pole of a sphere.

438
00:25:03.412 --> 00:25:09.377
And a qubit is anywhere, any location, latitude and longitude on the sphere.

439
00:25:09.477 --> 00:25:10.999
The sphere is called a block sphere.

440
00:25:11.359 --> 00:25:14.381
And this represents all of the different states that a qubit can be in.

441
00:25:14.742 --> 00:25:19.525
Okay, so crucially, there's two numbers that we have to keep track of.

442
00:25:19.746 --> 00:25:21.747
One is this way.

443
00:25:21.767 --> 00:25:23.569
This way is latitude.

444
00:25:23.589 --> 00:25:25.050
Yeah, this way is latitude, north-south.

445
00:25:25.410 --> 00:25:28.971
That's going to tell you how much it's aligned in zero or one.

446
00:25:28.991 --> 00:25:35.654
That's going to tell you if I were to measure the qubit, what's the probability that I'm going to get a zero and what's the probability that I'm going to get a one.

447
00:25:36.054 --> 00:25:39.996
If the qubit is at the north pole, then I'm going to get a zero all the time.

448
00:25:40.136 --> 00:25:42.637
If the qubit is on the south pole, I'm going to get a one all the time.

449
00:25:42.917 --> 00:25:44.338
And then there's also a phase.

450
00:25:44.578 --> 00:25:44.818
Right.

451
00:25:44.918 --> 00:25:45.918
There's the longitude.

452
00:25:46.218 --> 00:25:47.379
And that phase...

453
00:25:48.239 --> 00:25:50.060
is how the qubits interact with one another.

454
00:25:50.140 --> 00:25:57.566
It might not have to do with the probability at the very end, but it does have to do with how things get entangled, how they interfere, so on and so forth.

455
00:25:57.666 --> 00:26:12.637
And the phase is, even though we're looking at this visual as 0 or 1, basically northern hemisphere, southern hemisphere, the phase still matters for other types of interactions that are going to impact the system, even if it's not determinative of our 0 or 1.

456
00:26:12.717 --> 00:26:13.357
Exactly, yeah.

457
00:26:13.397 --> 00:26:16.139
So the qubit is that quantum version of a bit.

458
00:26:16.239 --> 00:26:17.080
It's some thingy.

459
00:26:17.982 --> 00:26:20.743
That's in your quantum computer that can do this.

460
00:26:21.183 --> 00:26:24.604
That can be a two-state system with quantum mechanics governing it.

461
00:26:24.724 --> 00:26:24.864
Yep.

462
00:26:25.104 --> 00:26:25.324
Okay?

463
00:26:25.624 --> 00:26:29.966
And a quantum computer effectively is a set of qubits that can be manipulated using quantum gates.

464
00:26:30.366 --> 00:26:32.747
Now, quantum gates we talked about in the last episode.

465
00:26:32.787 --> 00:26:38.408
These are unitary transformations that will rotate the qubits and put them together and things like that.

466
00:26:38.448 --> 00:26:40.029
They do not destroy information.

467
00:26:40.289 --> 00:26:40.469
Yes.

468
00:26:40.549 --> 00:26:40.809
Right?

469
00:26:41.429 --> 00:26:42.850
They are reversible.

470
00:26:42.970 --> 00:26:43.170
Yes.

471
00:26:43.470 --> 00:26:45.550
So they're not like the conventional AND gate.

472
00:26:45.570 --> 00:26:49.031
You need to have other strings attached in order to get this thing to work.

473
00:26:49.351 --> 00:26:54.492
You can go from either the question to the answer or the answer to the question in both ways.

474
00:26:54.552 --> 00:26:55.092
In both ways.

475
00:26:55.112 --> 00:26:56.512
A lot of times we talk about AND gates.

476
00:26:56.532 --> 00:26:58.733
You can only go from the question to the answer.

477
00:26:58.793 --> 00:26:59.173
Exactly.

478
00:26:59.193 --> 00:27:00.533
But you can't go back to the question.

479
00:27:00.573 --> 00:27:01.013
Exactly.

480
00:27:01.173 --> 00:27:02.214
Very good.

481
00:27:02.434 --> 00:27:03.994
And for a single qubit...

482
00:27:05.082 --> 00:27:06.062
We've got a lot of gates.

483
00:27:06.682 --> 00:27:09.863
You can rotate the qubit, as you showed in the block sphere.

484
00:27:09.943 --> 00:27:12.083
And here, in this case, this is called a Hadamard gate.

485
00:27:13.004 --> 00:27:16.904
This takes a single state, a quantum state, from a 0 or a 1.

486
00:27:17.164 --> 00:27:19.685
So it's in a pure state, either in the North Pole or the South Pole.

487
00:27:19.985 --> 00:27:22.105
And it puts that block sphere on the equator.

488
00:27:22.685 --> 00:27:22.945
Okay?

489
00:27:23.145 --> 00:27:29.547
So either you've got the 0 goes to the sum of 0 plus 1, and the 1 goes to 0 minus 1.

490
00:27:30.027 --> 00:27:31.107
Okay?

491
00:27:31.327 --> 00:27:31.587
Now...

492
00:27:33.872 --> 00:27:35.693
That's for single qubits.

493
00:27:35.973 --> 00:27:37.194
You know, that's the Hadamard gate.

494
00:27:37.474 --> 00:27:43.017
You can also think of these things as rotations on the Blocksphere, as I was saying, right?

495
00:27:43.137 --> 00:27:46.980
In this case, the Hadamard gate rotates along some direction in the Blocksphere.

496
00:27:47.300 --> 00:27:50.542
The Z gate rotates along the north-south axis.

497
00:27:50.702 --> 00:27:54.504
And then the Hadamard gate, again, rotates along one of the off-axes.

498
00:27:54.524 --> 00:27:55.765
So in order to get an X gate

499
00:27:56.265 --> 00:28:00.527
For example, an X gate is something where you rotate along the X axis of your sphere.

500
00:28:00.807 --> 00:28:05.889
You can put a bunch of gates together to get an X gate, for example.

501
00:28:05.929 --> 00:28:12.913
This is like one of those desk tchotchkes where you have the little sphere thingy and it has the three axes of rotation and you move it around.

502
00:28:12.933 --> 00:28:16.154
Yeah, like the toy gyroscopes, if you've ever seen.

503
00:28:16.214 --> 00:28:22.097
This is as a visual representation of what the math is doing or what we're talking about as we make these...

504
00:28:22.777 --> 00:28:23.738
transformations.

505
00:28:23.778 --> 00:28:24.678
Exactly, yeah.

506
00:28:24.778 --> 00:28:27.000
And that's what these single qubit gates do.

507
00:28:27.180 --> 00:28:27.540
Okay.

508
00:28:27.720 --> 00:28:30.522
You also need the qubits to interact, though, right?

509
00:28:30.542 --> 00:28:31.743
So you can have two qubit gates.

510
00:28:32.223 --> 00:28:37.607
And you can put a bunch of these two qubit gates together to create a quantum circuit.

511
00:28:38.207 --> 00:28:45.471
And the circuit is going to implement a quantum algorithm, like your Shores, like your Grovers, like your Deutsch-Jose, or whatever you want.

512
00:28:45.811 --> 00:28:56.636
And here you can see, like, you know, based on the state of one qubit, the block sphere of another qubit will rotate in one direction, you know, and they can get entangled and so on and so forth.

513
00:28:56.696 --> 00:28:58.097
All of the quantum magic that happens.

514
00:28:58.557 --> 00:29:02.660
The idea is the single gate is like a single instruction in a recipe.

515
00:29:03.681 --> 00:29:10.366
And then when we get to this idea of the entanglement display we just showed, it's like now we're stacking multiple individual instructions.

516
00:29:10.406 --> 00:29:10.646
Yeah.

517
00:29:10.887 --> 00:29:11.287
To be able to go.

518
00:29:11.307 --> 00:29:12.168
And they're interacting.

519
00:29:12.188 --> 00:29:13.469
And they're interacting with each other.

520
00:29:13.929 --> 00:29:14.349
Exactly.

521
00:29:14.369 --> 00:29:14.589
Yeah.

522
00:29:15.090 --> 00:29:18.913
And so now let's get into like what the classical qubits are today.

523
00:29:18.953 --> 00:29:20.334
Sorry, the classical bits, I should say.

524
00:29:20.654 --> 00:29:22.616
Transistors are the classical bits of today.

525
00:29:22.736 --> 00:29:24.838
Transistors are the stuff that's in our computer.

526
00:29:24.998 --> 00:29:25.198
Right.

527
00:29:25.318 --> 00:29:27.460
On our iPhone, in our da-da-da.

528
00:29:27.580 --> 00:29:28.361
Da-da-da.

529
00:29:28.381 --> 00:29:28.841
The car.

530
00:29:29.101 --> 00:29:29.222
Yes.

531
00:29:29.242 --> 00:29:30.723
This is why everyone loves Taiwan.

532
00:29:30.943 --> 00:29:31.343
Yeah.

533
00:29:31.403 --> 00:29:31.864
Right, right.

534
00:29:31.884 --> 00:29:32.925
TSMC, shout out.

535
00:29:33.005 --> 00:29:33.265
Yeah.

536
00:29:33.285 --> 00:29:34.886
Shout out to TSMC.

537
00:29:35.427 --> 00:29:41.032
And this is why geopolitically it's such an important thing for us because TSMC makes all of our transistors, all of our chips.

538
00:29:41.512 --> 00:29:45.916
Now, they were not the only classical bits out there, though.

539
00:29:46.076 --> 00:29:46.776
Historically...

540
00:29:47.477 --> 00:29:49.439
There's been a lot of different types of computers.

541
00:29:49.459 --> 00:29:53.202
There's been the imitation game with Alan Turing.

542
00:29:53.502 --> 00:29:56.465
He created a computer out of electronic relay switches.

543
00:29:56.805 --> 00:29:58.726
It does the same thing that a transistor does.

544
00:29:59.107 --> 00:30:00.668
It holds a zero and a one.

545
00:30:00.788 --> 00:30:02.830
And based on that, it can make logic.

546
00:30:03.631 --> 00:30:08.174
And he defeated the Nazis' code with his giant computer.

547
00:30:08.815 --> 00:30:09.756
Was it Enigma?

548
00:30:09.776 --> 00:30:11.077
Yeah, the Enigma code, exactly.

549
00:30:11.317 --> 00:30:13.719
And on the right-hand side, we've got John von Neumann,

550
00:30:13.959 --> 00:30:41.593
standing in front of his giant computer that's made out of vacuum tubes he's standing next to robert oppenheimer again another type of computer these things were giant though if you remember from the movie they took up an entire warehouse the vacuum tube stuff also took up an entire warehouse and it wasn't even like a megabyte worth of memory right or maybe it was like a megabyte but like a few the basically they were they worked but were inefficient because they required such size and scale that we're not going to be practical to be able to create iphones exactly

551
00:30:42.767 --> 00:30:46.049
Then we got the transistor out of Bell Labs, won the Nobel Prize.

552
00:30:46.229 --> 00:30:50.272
And lo and behold, all of these other technologies went into the museums.

553
00:30:50.752 --> 00:30:52.533
And what is a transistor made out of again?

554
00:30:52.553 --> 00:30:53.834
Oh, silicon.

555
00:30:54.074 --> 00:30:54.575
Oh, right.

556
00:30:54.595 --> 00:30:55.735
That's right.

557
00:30:56.776 --> 00:30:57.437
That's interesting.

558
00:30:57.697 --> 00:31:06.903
And I do want to make the, I think I'm seeing the parallel you're drawing here, which is, again, when you have a frontier technology, there are a lot of ways that people think are the best way to go about it.

559
00:31:07.183 --> 00:31:09.905
But there's a difference between what works and what works at scale.

560
00:31:10.005 --> 00:31:10.205
Yes.

561
00:31:10.225 --> 00:31:10.305
Yes.

562
00:31:10.706 --> 00:31:16.539
And we had vacuum tubes and electric relays that both did work.

563
00:31:16.579 --> 00:31:17.681
Yeah.

564
00:31:17.822 --> 00:31:18.844
No one's saying they didn't work.

565
00:31:19.425 --> 00:31:19.866
However...

566
00:31:21.068 --> 00:31:22.429
They would not have birthed the internet.

567
00:31:22.550 --> 00:31:36.161
They would not have birthed DoorDash, Uber, little robots you have for your kids every day because it could not scale, which is both a performance problem and a size problem, among other things.

568
00:31:36.741 --> 00:31:48.211
And so I'm just trying to re-bring up this parallel that I think you're trying to build here, which is, yes, there can be multiple ways to do some functional goal.

569
00:31:48.231 --> 00:31:48.331
Yeah.

570
00:31:49.233 --> 00:31:56.367
but it might not be the most efficient or best way to accomplish it if you ultimately want to make this a productized

571
00:31:57.364 --> 00:31:57.664
Something.

572
00:31:57.965 --> 00:31:58.565
Something, right?

573
00:31:58.905 --> 00:31:59.166
Something.

574
00:31:59.186 --> 00:32:00.587
You said it, not me.

575
00:32:01.047 --> 00:32:03.329
This wasn't even my opinion.

576
00:32:03.929 --> 00:32:07.272
I guess we're both drinking the Kool-Aid.

577
00:32:07.312 --> 00:32:10.014
The logic is falling in the gate.

578
00:32:10.115 --> 00:32:11.696
So with that in mind, right?

579
00:32:11.716 --> 00:32:19.502
With that background in mind about how classical computing, how the history of classical computing has unfolded, let's get into some of the history behind quantum computing.

580
00:32:19.542 --> 00:32:25.107
So in the previous episode, we went into Feynman's lecture at MIT where he talked about quantum computing,

581
00:32:25.387 --> 00:32:27.448
quantum simulation using a quantum computer.

582
00:32:28.628 --> 00:32:32.450
And that sort of started this, it was in 1980, I think.

583
00:32:33.330 --> 00:32:37.952
20 years after that, in those 20 years, people had started thinking about how to make a quantum computer.

584
00:32:37.972 --> 00:32:41.073
And there were all these different proposals out there.

585
00:32:41.953 --> 00:32:47.135
In 2000, David DiVincenzo, he published his famous five criteria.

586
00:32:48.996 --> 00:32:52.357
The paper was titled, The Physical Implementation of Quantum Computation.

587
00:32:52.377 --> 00:32:54.578
He was actually at the IBM Watson Research Center.

588
00:32:55.121 --> 00:32:56.122
That'll come back in the future.

589
00:32:56.142 --> 00:32:56.743
That'll come back.

590
00:32:56.803 --> 00:33:00.166
So IBM has a rich legacy in quantum computation.

591
00:33:01.587 --> 00:33:08.574
So he wrote this paper, and he wanted to lay down the baseline physics for what you need to build one of these things.

592
00:33:09.295 --> 00:33:14.920
And it was brilliant for its time, mostly because it was designed to politely tell the liquid state,

593
00:33:15.300 --> 00:33:33.920
NMR crowd, the nuclear magnetic resonance crowd, hey let's not pretend that your little physics experiment is actually a big step towards quantum computation it was mostly like targeted specifically for these guys who were using NMR to say oh we've got like you know, we can use this as a qubit

594
00:33:34.660 --> 00:33:48.508
In particular, he was skeptical of approaches of this liquid state NMR quantum computing, which in the late 90s, 1990s, it had achieved small logic gates, but highly mixed, not fully pure quantum states.

595
00:33:49.249 --> 00:33:56.553
So NMR could perform computation on, let's say, an ensemble of molecules, but it couldn't even initialize a zero or a one.

596
00:33:57.713 --> 00:33:57.934
Right?

597
00:33:57.954 --> 00:34:00.375
So DiVincenzo is writing there, and he...

598
00:34:01.803 --> 00:34:25.069
explicitly includes the terms scalable fiducial which means pure initial state um and these are warning phrases that were pointed at the nmr crowd yeah he's basically saying you don't you don't have the juice yeah yeah uh you can't like hand wave your way out of not having the ability to scale and not having pure initial states exactly

599
00:34:25.149 --> 00:34:30.475
Yeah, and so over 20 years on, the DiVincenzo criteria is still very relevant, but it's 2026 now.

600
00:34:31.076 --> 00:34:35.721
And almost every modality can demonstrate a cubit in a vacuum.

601
00:34:36.221 --> 00:34:45.511
Not everything can do what DiVincenzo's criteria is doing, but in line of DiVincenzo targeting a specific modality...

602
00:34:46.512 --> 00:34:57.357
For the negative, we here at From First Principles have created an FFP audit that is going to also target a specific modality, but in the positive.

603
00:34:57.537 --> 00:34:57.757
Yes.

604
00:34:58.257 --> 00:34:58.437
Right?

605
00:34:58.497 --> 00:34:59.298
Because we can do that.

606
00:34:59.318 --> 00:35:00.919
This is the FFP criteria.

607
00:35:00.959 --> 00:35:01.719
Yes.

608
00:35:01.739 --> 00:35:03.320
This is DiVincenzo 2.0.

609
00:35:04.080 --> 00:35:06.001
FFP criteria, trademark pending.

610
00:35:06.161 --> 00:35:06.621
Pending.

611
00:35:07.561 --> 00:35:09.322
So don't come at us.

612
00:35:09.442 --> 00:35:10.263
We're going to sue you.

613
00:35:10.283 --> 00:35:12.684
We've got the legal system on our back.

614
00:35:14.744 --> 00:35:21.026
So we're going to think about three criteria about what makes a good quantum computer.

615
00:35:21.246 --> 00:35:21.486
Okay?

616
00:35:22.606 --> 00:35:27.667
Qubit quality, qubit control, and the scalability and the economics of the thing.

617
00:35:28.227 --> 00:35:28.427
All right.

618
00:35:28.447 --> 00:35:30.088
So let's get into what each of these things mean.

619
00:35:30.288 --> 00:35:30.448
Yep.

620
00:35:30.568 --> 00:35:31.808
So qubit quality.

621
00:35:32.248 --> 00:35:32.488
All right.

622
00:35:32.528 --> 00:35:33.468
So you've made a qubit.

623
00:35:34.589 --> 00:35:36.549
Question is, how hard is it to keep isolated?

624
00:35:36.569 --> 00:35:36.789
Yeah.

625
00:35:38.291 --> 00:35:39.674
How long does it last?

626
00:35:40.235 --> 00:35:47.288
If your qubit doesn't last very long and you need more time to poke it around with your quantum circuit...

627
00:35:48.090 --> 00:35:54.311
to get an answer, and by the time the circuit has ended, your qubit has failed, well, you're kind of done, right?

628
00:35:54.351 --> 00:35:54.532
Yes.

629
00:35:54.592 --> 00:36:03.094
So the gates that you saw in those rotations, those rotations need to happen much faster than the qubit can forget what it is.

630
00:36:03.274 --> 00:36:05.914
The entanglement states that we had seen in the previous.

631
00:36:05.974 --> 00:36:06.694
Yeah.

632
00:36:07.195 --> 00:36:12.596
The idea again here is efficiency and data fidelity.

633
00:36:12.796 --> 00:36:13.016
Mm-hmm.

634
00:36:13.476 --> 00:36:14.196
That's exactly right.

635
00:36:14.236 --> 00:36:14.797
Yeah.

636
00:36:14.877 --> 00:36:25.803
The qubit quality is effectively how efficient is the circuit that you're going to implement in relation to how long your qubit can last, right?

637
00:36:25.843 --> 00:36:30.025
For example, if you take a bunch of transistors and you're trying to do AND gates on them, right?

638
00:36:30.565 --> 00:36:39.550
If the transistor forgets if it's a zero and a one before you can even implement the AND gate, then the thing you're going to get out of the AND gate is not really going to be the AND of the two.

639
00:36:39.570 --> 00:36:39.750
Right.

640
00:36:40.030 --> 00:36:41.731
It's going to be some random zero or one.

641
00:36:42.732 --> 00:36:44.553
I'd like to actually do computation.

642
00:36:44.853 --> 00:36:46.574
And so the transistor better be stable.

643
00:36:46.854 --> 00:36:48.995
Well, in the quantum sense, it's very similar.

644
00:36:49.055 --> 00:36:57.180
The decoherence time is what we call it, of how long the qubit can remember itself and not get messed around with all of the outside noise.

645
00:36:58.121 --> 00:37:00.502
That needs to be much larger than the gate time.

646
00:37:01.082 --> 00:37:01.243
Right?

647
00:37:02.727 --> 00:37:06.848
And that brings us to another question, which is how does it compare to your, like, what's the noise sources?

648
00:37:07.228 --> 00:37:08.388
That has to do with the qubit quality.

649
00:37:08.408 --> 00:37:10.129
What are the noise sources and can you get rid of them?

650
00:37:10.209 --> 00:37:10.609
Exactly.

651
00:37:10.769 --> 00:37:11.169
Okay.

652
00:37:11.249 --> 00:37:12.209
So that's qubit quality.

653
00:37:12.249 --> 00:37:21.431
Then there is qubit control, which is can you initialize, manipulate, and read out the state without your control rack setting on fire?

654
00:37:22.371 --> 00:37:22.571
Right?

655
00:37:22.931 --> 00:37:25.172
Initialize meaning like state preparation.

656
00:37:25.192 --> 00:37:25.552
Mm-hmm.

657
00:37:26.508 --> 00:37:29.629
So, you know, preparing all of your qubits in the zero state.

658
00:37:29.769 --> 00:37:29.949
Yeah.

659
00:37:30.069 --> 00:37:31.309
That's something Anamar couldn't do.

660
00:37:31.510 --> 00:37:31.630
Yeah.

661
00:37:31.750 --> 00:37:33.850
Which is why DiVincenzo wrote that thing in the first place.

662
00:37:33.870 --> 00:37:34.911
It's the pure initial state point.

663
00:37:35.071 --> 00:37:35.471
Exactly.

664
00:37:35.491 --> 00:37:41.373
Where we see the blue in the left where it's like we all have, we have to start everything at a known base.

665
00:37:41.533 --> 00:37:41.733
Yeah.

666
00:37:42.233 --> 00:37:46.314
Like it better, like I better know the states of my system before I start doing quantum logic, right?

667
00:37:46.574 --> 00:37:47.895
Otherwise, like what are we doing?

668
00:37:48.015 --> 00:37:48.155
Right.

669
00:37:48.215 --> 00:37:48.535
Right.

670
00:37:49.607 --> 00:37:52.108
And then can I manipulate them with my gates?

671
00:37:52.569 --> 00:37:53.609
And then can I read it out?

672
00:37:53.669 --> 00:37:56.431
Can I measure what the thing actually is?

673
00:37:56.831 --> 00:37:57.031
Right?

674
00:37:57.751 --> 00:38:05.275
Now, when it comes to manipulation and gate fidelity, this middle part right here, here's where the noise directly translates into error rates.

675
00:38:05.735 --> 00:38:07.997
Because the question is...

676
00:38:09.177 --> 00:38:20.123
Can you reliably hit, let's say, two qubit gates, two qubit gates where you take one qubit and another qubit and let's say you want to entangle them or you want to rotate one based on the state of the other?

677
00:38:20.303 --> 00:38:22.505
Like if the other one is near a one, then I rotate.

678
00:38:22.865 --> 00:38:24.706
If not, then that's called a controlled knot.

679
00:38:25.006 --> 00:38:26.267
Can I just take a moment here?

680
00:38:26.287 --> 00:38:29.769
Because I think this is a really key idea to make sure that people are getting right.

681
00:38:29.789 --> 00:38:37.113
So we talked about earlier when we have these cubic gates that there's two states.

682
00:38:37.973 --> 00:38:42.255
One of them is, again, to simplify it, North Pole, South Pole.

683
00:38:42.635 --> 00:38:46.097
And then the other one is like where in that north or it's northern or southern.

684
00:38:46.117 --> 00:38:47.098
Where in the longitude.

685
00:38:47.438 --> 00:38:48.198
East, west.

686
00:38:48.539 --> 00:38:49.019
East, west.

687
00:38:49.039 --> 00:38:49.319
How far?

688
00:38:49.619 --> 00:38:50.820
We can even just call it that.

689
00:38:50.840 --> 00:38:51.560
Let's just call it that.

690
00:38:51.580 --> 00:38:52.781
North, south, east, west.

691
00:38:55.022 --> 00:38:58.047
North-south can be just a zero or one.

692
00:38:58.067 --> 00:39:02.974
It can just be a functional answer that we can then move on in whatever our process is.

693
00:39:03.415 --> 00:39:06.860
But when you just talked about, for example, when we start having two –

694
00:39:08.140 --> 00:39:13.062
like two of these states, two of these qubits interacting with each other.

695
00:39:13.602 --> 00:39:16.183
The phase is maybe what matters more.

696
00:39:16.743 --> 00:39:19.264
The east-west is maybe what matters more than the north-south.

697
00:39:19.324 --> 00:39:21.704
Yeah, I mean, sometimes, well, it depends on the gate, really.

698
00:39:21.964 --> 00:39:27.126
But I think your point being that both of these directions matter.

699
00:39:27.286 --> 00:39:28.106
Right, right.

700
00:39:28.166 --> 00:39:30.387
In terms of what the next one is.

701
00:39:31.147 --> 00:39:32.429
Does or does not do.

702
00:39:33.090 --> 00:39:41.662
And the ability for those two things to interact successfully in this quantum state is meaningful.

703
00:39:41.682 --> 00:39:43.264
Like that's this orange band.

704
00:39:43.385 --> 00:39:43.905
Yeah.

705
00:39:43.925 --> 00:39:45.187
That's the computation part.

706
00:39:45.468 --> 00:39:45.868
Okay.

707
00:39:45.988 --> 00:39:46.769
And I just wanted to.

708
00:39:46.809 --> 00:39:47.550
That's exactly right.

709
00:39:47.571 --> 00:39:47.771
Okay.

710
00:39:48.031 --> 00:39:53.535
And the point that I'm trying to make over here is that when we do these gates, they're not going to be 100%.

711
00:39:53.795 --> 00:40:12.186
It's not like classical computing where the transistor, if I wanted to flip that transistor, unless like a cosmic ray comes in or some nonsense, or unless I'm operating the computer at like 200 degrees Celsius, if I want to flip the bit from a 0 to a 1 or back and forth, that thing is going to flip, right?

712
00:40:12.286 --> 00:40:16.349
It's extremely reliable because it depends on like bulk electronics.

713
00:40:16.369 --> 00:40:16.629
Right?

714
00:40:17.057 --> 00:40:20.718
Here, it's depending on single qubits, right?

715
00:40:20.838 --> 00:40:22.379
These are very finicky things.

716
00:40:23.559 --> 00:40:32.683
And so there's a chance that you try to flip something or you try to rotate something and it just doesn't work because of whatever reason.

717
00:40:32.763 --> 00:40:33.063
For sure.

718
00:40:33.243 --> 00:40:33.483
Right?

719
00:40:34.143 --> 00:40:35.904
You need to bring that chance down.

720
00:40:37.024 --> 00:40:38.705
You need to be able to do this correctly.

721
00:40:39.628 --> 00:41:06.987
reliably this is the qubit control point which is the criterion number two because this is a highly um volatile system or or a highly um uh maybe volatile is not the right word but no volatile yeah i would say and so but this is the and i'm trying to nail down this point which is by nature it's not like transistors no where you're always going to get a zero or you're always going to get a one based on some yeah and if you want to flip it it's going to flip

722
00:41:07.667 --> 00:41:20.376
Because of that, the cubic control really does – is like a very important – in this computation layer especially is like a lot of – there's a lot of meat there to actually nail down.

723
00:41:20.436 --> 00:41:21.797
Yeah, and you better be good at it.

724
00:41:21.837 --> 00:41:22.737
And you better be good at it.

725
00:41:22.777 --> 00:41:22.977
Yeah.

726
00:41:23.278 --> 00:41:25.159
And you're not going to get perfect.

727
00:41:25.759 --> 00:41:29.001
You're never going to get perfect because quantum mechanics is a probabilistic thing.

728
00:41:29.202 --> 00:41:31.903
You're living not at absolute zero, blah, blah, blah.

729
00:41:31.923 --> 00:41:32.124
Yes.

730
00:41:32.244 --> 00:41:36.286
So one of the tricks that people use is they use –

731
00:41:37.907 --> 00:41:39.328
redundancy, effectively.

732
00:41:39.728 --> 00:41:39.909
Okay.

733
00:41:39.949 --> 00:41:49.736
Where several qubits are performing a computation, and loosely speaking, you do a voting type thing.

734
00:41:49.796 --> 00:41:53.419
All of these different qubits are performing a computation, and then you vote on...

735
00:41:53.679 --> 00:41:54.520
what the actual thing is.

736
00:41:54.540 --> 00:42:00.764
That way, if some people failed, you can still have a sense of what the algorithm actually is, right?

737
00:42:00.784 --> 00:42:02.145
This is called error correction.

738
00:42:02.205 --> 00:42:12.333
Because there's going to be errors, but there's ways to mitigate for that error by assigning multiple physical qubits to a logical qubit.

739
00:42:12.473 --> 00:42:14.054
A logical qubit is your block sphere.

740
00:42:14.074 --> 00:42:16.736
That's the thing that the algorithm is operating on, right?

741
00:42:16.796 --> 00:42:22.581
And if you've got multiple physical qubits that are kind of keeping track of this information, loosely speaking,

742
00:42:23.281 --> 00:42:25.262
you can form a redundancy.

743
00:42:25.302 --> 00:42:35.329
Now, it's a little bit trickier than that because there's this famous thing called the no-cloning theorem in quantum mechanics where you can't clone information, but you can get around it.

744
00:42:35.349 --> 00:42:39.833
You're not really cloning information, but you're still keeping track of it on multiple physical...

745
00:42:40.481 --> 00:42:44.383
Qubits, physical qubits, meaning whatever, your superconducting circuit, your trapped ion, whatever.

746
00:42:44.604 --> 00:42:49.727
You've got a multiple of these to create a single logical qubit, and the logical qubit is the thing that is doing the algorithm.

747
00:42:50.287 --> 00:42:55.070
And so there's almost – now in a system-level case, and I know maybe we're getting a little hell of ourselves.

748
00:42:55.090 --> 00:42:55.690
We can come back.

749
00:42:55.730 --> 00:42:59.693
There's this idea that there are qubits that have different functional purposes.

750
00:43:00.393 --> 00:43:01.274
One might be tracking.

751
00:43:01.294 --> 00:43:01.674
Tracking.

752
00:43:01.814 --> 00:43:04.756
and one might be doing the actual calculation.

753
00:43:04.796 --> 00:43:04.996
Yeah.

754
00:43:05.356 --> 00:43:09.759
And you can have some combination of these different types of qubits to get to a system.

755
00:43:09.779 --> 00:43:16.423
Because in order to have a system, you need a goalkeeper, you need back four, you need your midfield, you need the guys who are going to score goals.

756
00:43:16.583 --> 00:43:16.923
Exactly.

757
00:43:16.943 --> 00:43:19.624
And so qubits sort of take roles accordingly.

758
00:43:19.644 --> 00:43:20.045
Very good.

759
00:43:20.065 --> 00:43:21.485
Yeah, no, that's a really good analogy.

760
00:43:21.506 --> 00:43:22.106
Okay, okay, okay.

761
00:43:22.266 --> 00:43:23.026
Yeah.

762
00:43:23.387 --> 00:43:25.148
And so that's exactly right.

763
00:43:25.208 --> 00:43:30.211
And so when we think about, like, you know, noisy physical qubits versus –

764
00:43:31.071 --> 00:43:34.693
the logical qubits that we're trying to emulate in this like logical space.

765
00:43:34.733 --> 00:43:35.533
Yeah.

766
00:43:35.793 --> 00:43:40.495
The only thing that really matters is fault tolerant quantum computing.

767
00:43:40.515 --> 00:43:46.678
This is, this is kind of a big thing these days, which is, you know, suppose there's a, like a bit flip error.

768
00:43:47.618 --> 00:43:50.741
Or there's a phase flip error where it's on east.

769
00:43:51.261 --> 00:43:57.526
It's like 90 degrees east, and then whoop, all of a sudden it's like 90 degrees west because, I don't know, some random photon came in from somewhere.

770
00:43:57.807 --> 00:44:00.629
Or there was like some charge, blah.

771
00:44:00.789 --> 00:44:04.912
Bit flip error, it was in the north axis, and then whoop, went to the south axis.

772
00:44:05.253 --> 00:44:05.713
No reason.

773
00:44:06.073 --> 00:44:06.253
Right.

774
00:44:06.293 --> 00:44:07.835
Just quantum stuff.

775
00:44:07.915 --> 00:44:08.135
Yes.

776
00:44:08.355 --> 00:44:10.057
Quantum stuff happening, right?

777
00:44:12.098 --> 00:44:15.281
If that happens, you better have these error-correcting codes...

778
00:44:15.845 --> 00:44:30.538
There's a fancy way of saying that there's some computational machinery that I can implement that is going to keep track of the lost information and keep track of where I'm trying to go with the algorithm.

779
00:44:30.858 --> 00:44:37.884
And with that redundancy, I'm still able to compute whatever algorithm or circuit that I was trying to compute in the first place.

780
00:44:37.984 --> 00:44:38.144
Got it.

781
00:44:38.364 --> 00:44:44.608
This is not like a no-go deal breaker if one of these errors happens.

782
00:44:44.869 --> 00:44:45.269
Makes sense.

783
00:44:45.849 --> 00:44:49.091
There's the ability to detect and fix in post.

784
00:44:49.612 --> 00:44:50.352
We'll do it in post.

785
00:44:50.452 --> 00:44:51.213
Yeah, exactly.

786
00:44:51.493 --> 00:44:54.235
So I better be able to do this very well, right?

787
00:44:54.255 --> 00:44:57.777
Because every single physical qubit is going to have these types of problems.

788
00:44:57.897 --> 00:45:00.639
And this is this idea of fault-tolerant quantum computing.

789
00:45:00.659 --> 00:45:04.442
Yeah, so whenever you hear fault-tolerant quantum computing, the fault...

790
00:45:05.102 --> 00:45:05.523
Is this.

791
00:45:05.543 --> 00:45:06.544
Is these errors.

792
00:45:06.764 --> 00:45:10.047
It's either going north when it should be south or east when it should be west.

793
00:45:10.067 --> 00:45:10.307
Yeah.

794
00:45:10.367 --> 00:45:11.068
Or it's, yeah.

795
00:45:11.208 --> 00:45:12.990
And it can be more complicated than this, right?

796
00:45:13.010 --> 00:45:13.210
For sure.

797
00:45:13.230 --> 00:45:15.433
It could be like multiple qubits are doing weird things.

798
00:45:15.533 --> 00:45:15.873
For sure.

799
00:45:16.033 --> 00:45:16.253
Right?

800
00:45:16.293 --> 00:45:16.734
For sure.

801
00:45:16.974 --> 00:45:17.755
To keep it simple.

802
00:45:17.775 --> 00:45:20.237
But to keep it simple, this is like one of the common ones, right?

803
00:45:20.257 --> 00:45:20.558
Yeah.

804
00:45:20.938 --> 00:45:22.540
It was north, now all of a sudden it's south.

805
00:45:22.780 --> 00:45:23.120
Fair enough.

806
00:45:23.240 --> 00:45:25.463
But if all of its neighbors are like, yo, you should...

807
00:45:26.003 --> 00:45:26.663
We're all north.

808
00:45:26.803 --> 00:45:28.304
It's a combinatorial thing.

809
00:45:28.344 --> 00:45:30.164
It's like, because, yeah.

810
00:45:30.204 --> 00:45:35.606
So it is both at an individual level and then you have to zoom out to then how does that impact the system?

811
00:45:35.726 --> 00:45:35.946
Yeah.

812
00:45:36.006 --> 00:45:38.627
And so the complexity can get quite ridiculous.

813
00:45:38.707 --> 00:45:39.127
Exactly.

814
00:45:39.147 --> 00:45:39.647
Yeah.

815
00:45:39.667 --> 00:45:45.989
And one of the key things that matters with these types of fault tolerant computing is what is the connectivity of your qubits?

816
00:45:46.709 --> 00:45:49.670
For example, like if you're only, if you're all on a line.

817
00:45:50.902 --> 00:45:53.264
I can only talk to the qubit behind me and in front of me.

818
00:45:53.765 --> 00:45:53.985
Right.

819
00:45:54.766 --> 00:45:58.249
Um, if I'm in a square lattice, then I can talk to like four of my nearest neighbors.

820
00:45:58.289 --> 00:45:59.030
Right.

821
00:45:59.290 --> 00:45:59.831
But if I'm,

822
00:46:00.287 --> 00:46:06.954
all-to-all connected, like some of the ones that we're going to see claim, then I can talk to literally every single one somehow, right?

823
00:46:07.055 --> 00:46:10.018
And then my error code can be that much more efficient.

824
00:46:10.458 --> 00:46:15.364
So maybe I don't need that many physical qubits to encode a logical qubit, right?

825
00:46:15.424 --> 00:46:18.788
Because I've got larger quorum sensing in some sense.

826
00:46:18.888 --> 00:46:20.930
A side note, in biology, we...

827
00:46:21.150 --> 00:46:23.271
like biological systems do this all the time.

828
00:46:24.432 --> 00:46:31.055
For example, when you're an embryo and like your cells are just a ball of stem cells, right?

829
00:46:31.455 --> 00:46:34.956
But then each cell has to decide, I'm going to go be the head.

830
00:46:35.377 --> 00:46:36.537
I'm going to go be the tail.

831
00:46:36.677 --> 00:46:38.098
I'm going to go be a hand.

832
00:46:38.438 --> 00:46:40.699
I'm going to go be a liver cell, so on and so forth.

833
00:46:41.079 --> 00:46:44.401
How does the cell know where it is in the embryo, right?

834
00:46:44.601 --> 00:46:47.022
How come I don't have a liver in my skull?

835
00:46:47.182 --> 00:46:47.382
Right.

836
00:46:47.642 --> 00:46:47.822
Right.

837
00:46:47.862 --> 00:46:51.045
How come a cell near my skull didn't decide I'm going to go be a liver?

838
00:46:51.805 --> 00:47:04.656
It's because there's this idea called quorum sensing in biology, where in order to figure out where they are spatially in an embryo and who gets to do what, they start aggregating votes.

839
00:47:05.216 --> 00:47:10.439
from their neighbors to try to bring that noise down and figure out, okay, so I'm definitely liver, right, guys?

840
00:47:10.479 --> 00:47:13.141
And then everyone around is like, yeah, because I'm going to be spleen.

841
00:47:13.321 --> 00:47:15.803
I'm going to be stomach, so you better be liver.

842
00:47:15.883 --> 00:47:21.827
It's kind of cool that that's the kind of stuff that I used to study in a little undergrad project, and now, you know...

843
00:47:22.263 --> 00:47:26.888
The, you know, physics is connected, even from biophysics to quantum physics.

844
00:47:26.908 --> 00:47:30.551
This is why when you're playing on a squad with 11 players, you have to communicate.

845
00:47:30.991 --> 00:47:43.844
Because the difference between a team that communicates and doesn't is players that are in there, the right and correct position to execute the tactical approach of the day versus a team that doesn't communicate and then players in the wrong spot.

846
00:47:44.164 --> 00:47:46.106
And we saw that live with Belgium versus USA.

847
00:47:49.968 --> 00:47:51.430
We will not talk about it.

848
00:47:51.470 --> 00:47:52.271
It was depressing.

849
00:47:53.012 --> 00:47:53.872
That was pretty bad.

850
00:47:53.952 --> 00:47:55.254
But that's exactly what happened.

851
00:47:55.274 --> 00:47:56.255
But that's exactly what happened.

852
00:47:56.595 --> 00:48:06.385
And so this is actually very helpful because now we're kind of setting the basis of like, okay, we now – this criteria, we talked about two points so far.

853
00:48:07.266 --> 00:48:17.756
We talked about qubit quality, the ability to maintain itself, and then qubit control over those three stages, the initialization, the actual computation, and the measurement.

854
00:48:19.318 --> 00:48:21.180
How well are you able to control?

855
00:48:21.840 --> 00:48:24.643
Even if you have good qubit quality, you can have bad qubit control.

856
00:48:24.663 --> 00:48:27.145
You can have good qubit control, but bad qubit quality.

857
00:48:27.165 --> 00:48:27.666
Exactly.

858
00:48:27.686 --> 00:48:28.447
You better be good at both.

859
00:48:28.467 --> 00:48:29.307
You better be good at both.

860
00:48:30.008 --> 00:48:39.172
And then that's leading us now to the final one, the final piece in our FFP criteria, trademark, which is scalability and economics.

861
00:48:39.232 --> 00:48:39.472
Okay.

862
00:48:39.512 --> 00:48:39.752
Okay.

863
00:48:40.092 --> 00:48:45.395
This is where the, the, this is where the startup pitch decks collide with reality.

864
00:48:45.935 --> 00:48:53.623
They collide with the laws of thermodynamics and the laws of economics, which are not real laws, which is why the economics Nobel Prize is not a real Nobel Prize.

865
00:48:53.724 --> 00:48:54.184
Okay.

866
00:48:54.705 --> 00:48:55.245
Had to say it.

867
00:48:55.566 --> 00:49:00.911
But when someone says we've got 100 cubits today and our roadmap is that we're going to have a million cubits.

868
00:49:02.454 --> 00:49:03.054
In five years.

869
00:49:03.735 --> 00:49:04.035
Okay.

870
00:49:04.895 --> 00:49:05.176
Really?

871
00:49:05.416 --> 00:49:05.736
Are you?

872
00:49:05.876 --> 00:49:06.096
Yeah.

873
00:49:06.317 --> 00:49:06.677
Are you?

874
00:49:07.958 --> 00:49:08.899
I don't believe you.

875
00:49:08.979 --> 00:49:09.259
Yeah.

876
00:49:09.359 --> 00:49:10.140
Yeah.

877
00:49:11.121 --> 00:49:13.102
There should be some salt in that.

878
00:49:13.122 --> 00:49:13.943
Okay.

879
00:49:14.423 --> 00:49:16.385
So first of all, how much cooling are you going to need?

880
00:49:17.045 --> 00:49:18.326
That's a big question that you should ask.

881
00:49:18.346 --> 00:49:18.667
Okay.

882
00:49:18.687 --> 00:49:19.587
Because quantum...

883
00:49:20.468 --> 00:49:22.171
Things are finicky.

884
00:49:22.851 --> 00:49:23.132
Okay?

885
00:49:23.572 --> 00:49:31.583
And you have to talk about the biggest, loudest, and most obnoxious problem in the universe when it comes to maintaining quantum information, and that is heat.

886
00:49:31.984 --> 00:49:37.431
So heat is the amount of jiggle and the amount of entropy—sorry, the amount of energy in any—

887
00:49:38.032 --> 00:49:39.413
degree of freedom of a system.

888
00:49:39.713 --> 00:49:51.639
For example, the heat in this room, right now the room is about 70 degrees Fahrenheit, so I don't know, let's say like 200, no, like 290 Kelvin above absolute zero.

889
00:49:52.419 --> 00:49:54.841
So 290 degrees Celsius above absolute zero.

890
00:49:55.181 --> 00:50:05.286
What that means is that the molecules in our room have an average amount of kinetic energy that is proportional to 270

891
00:50:07.857 --> 00:50:11.420
the number multiplied by something called Boltzmann's constant.

892
00:50:11.900 --> 00:50:12.120
Okay.

893
00:50:12.160 --> 00:50:18.865
And the Boltzmann's constant is literally just, it's like a, a, a tally trick.

894
00:50:18.905 --> 00:50:19.205
Yeah.

895
00:50:19.373 --> 00:50:21.695
for us to convert from temperature to energy.

896
00:50:21.995 --> 00:50:22.595
Okay?

897
00:50:22.935 --> 00:50:30.420
If I were to, if a physicist were to invent a new society, we would be measuring temperature and energy with the same scale.

898
00:50:30.440 --> 00:50:32.662
There would not be a Kelvin and a Joule.

899
00:50:32.722 --> 00:50:35.303
There would just be FFP.

900
00:50:35.383 --> 00:50:37.505
That's what we would call it.

901
00:50:37.525 --> 00:50:39.106
Which represents it both across both systems.

902
00:50:39.126 --> 00:50:40.707
Because both things are the same thing, really.

903
00:50:40.747 --> 00:50:44.790
Temperature is the amount of energy on average in every single degree of freedom.

904
00:50:45.230 --> 00:50:45.450
Now...

905
00:50:46.527 --> 00:50:49.789
In classical computers, this doesn't matter so much.

906
00:50:50.229 --> 00:50:51.030
Okay?

907
00:50:51.190 --> 00:50:54.051
Unless you get up to like 100 degrees Celsius, 400 Kelvin.

908
00:50:54.131 --> 00:50:58.574
I mean, you know, we did cover a recent paper where it got all the way up to 1,000 Kelvin.

909
00:50:58.594 --> 00:50:58.814
Yes.

910
00:50:59.114 --> 00:50:59.454
Right?

911
00:50:59.654 --> 00:51:00.455
And it was fine.

912
00:51:00.535 --> 00:51:01.015
It was fine.

913
00:51:01.295 --> 00:51:08.860
But that was a weird memristor made out of graphene and tungsten and all this other stuff.

914
00:51:08.880 --> 00:51:11.321
But like our normal computer, like, it's going to fail.

915
00:51:11.541 --> 00:51:11.721
Right?

916
00:51:11.781 --> 00:51:14.243
Because there's going to be so much movement.

917
00:51:14.883 --> 00:51:19.264
of electrons and so much jiggling of the atoms that it's going to destroy whatever computation is happening.

918
00:51:19.444 --> 00:51:19.584
Yep.

919
00:51:19.644 --> 00:51:19.824
Right?

920
00:51:20.204 --> 00:51:22.725
Now, but that's at like 100 degrees Celsius, 400 Kelvin.

921
00:51:23.185 --> 00:51:25.566
A qubit is incredibly delicate, though.

922
00:51:25.886 --> 00:51:26.106
Okay?

923
00:51:26.126 --> 00:51:31.027
The energy difference between a qubit's zero and its one state is microscopic.

924
00:51:31.047 --> 00:51:39.829
We're measuring this stuff in terms of electron volts, which is the amount of energy that it takes to move an electron up one volt, a single electron.

925
00:51:39.849 --> 00:51:40.829
Yeah, which is...

926
00:51:40.969 --> 00:51:41.829
It's minuscule.

927
00:51:41.909 --> 00:51:44.190
And if the ambient energy of the environment...

928
00:51:45.010 --> 00:51:48.131
is larger than the energy gap of your qubit, right?

929
00:51:48.211 --> 00:51:52.171
Imagine I've got two states, my zero and my one, which is the qubit.

930
00:51:54.512 --> 00:51:57.712
Whatever thingy, whether it's superconducting, and we'll get into what these states are.

931
00:51:57.952 --> 00:52:06.534
But imagine I've got a two-state system where the system can be in this spot or it can be in another spot, and the energy difference to jump from one to the other is some amount.

932
00:52:07.094 --> 00:52:13.155
But the amount of energy in the environment that's knocking you around is larger than that amount.

933
00:52:13.815 --> 00:52:20.665
Well, then, if I prepared, right, I'd like to prepare my qubit in the zero state, well, pretty soon it's just going to go into a mix of the two.

934
00:52:20.685 --> 00:52:22.888
It's going to bounce around between the two, right?

935
00:52:23.329 --> 00:52:27.695
It reminds me of, like, imagine, for example, you're in a car.

936
00:52:28.917 --> 00:52:33.402
And you've got like one of those beach balls, Earth beach balls in the passenger seat.

937
00:52:34.203 --> 00:52:35.725
As opposed to those Mars beach balls.

938
00:52:35.785 --> 00:52:36.426
Yeah, yeah, yeah.

939
00:52:36.486 --> 00:52:37.827
No, I ain't going to Mars.

940
00:52:38.208 --> 00:52:44.915
I'm trying to get Earth beach ball and the North Pole is pointing north in your passenger seat and the South Pole is pointing south in your passenger seat.

941
00:52:45.296 --> 00:52:49.020
If you're on a pristine road in, I don't know, like Switzerland…

942
00:52:49.600 --> 00:52:49.820
Right.

943
00:52:50.040 --> 00:52:51.961
And there's no curves and you're just going straight.

944
00:52:52.441 --> 00:52:59.824
That beach ball, once you prepare it in the zero and one in the North Pole spacing up, right, the Earth looks like the Earth.

945
00:53:00.145 --> 00:53:02.946
And I just keep driving because the road is so smooth.

946
00:53:03.866 --> 00:53:05.367
The beach ball is going to stay in that.

947
00:53:06.428 --> 00:53:13.337
But if I go into a New York City ridden pothole street, which Mom Donnie fixed, good for him, by the way.

948
00:53:13.377 --> 00:53:14.278
Good for him.

949
00:53:14.318 --> 00:53:16.300
Good for Mom Donnie that he fixed all those potholes.

950
00:53:16.320 --> 00:53:22.428
But before the fixing of the potholes, if I was driving down a New York street, the road would be bumpy.

951
00:53:24.035 --> 00:53:30.359
And the bumps would impart an energy into my beach ball that would start turning it.

952
00:53:31.139 --> 00:53:34.261
And there's some amount of energy that's required to keep this thing upright.

953
00:53:34.521 --> 00:53:40.245
But if I'm bumping enough, then this thing can be in any which way, any which direction.

954
00:53:40.785 --> 00:53:41.345
That's the point.

955
00:53:42.046 --> 00:53:45.668
So I need to isolate thermal noise from my system.

956
00:53:45.688 --> 00:53:45.968
Right.

957
00:53:46.308 --> 00:53:48.809
And this goes back to the how good is your cooling?

958
00:53:48.850 --> 00:53:53.272
Because basically you're saying how good is the suspension in your car when you hit a pothole?

959
00:53:53.432 --> 00:53:53.912
Exactly.

960
00:53:53.932 --> 00:53:54.833
Yeah.

961
00:53:54.893 --> 00:54:00.396
Is it really nice where you don't – and get rid of the jiggle for the beach ball?

962
00:54:00.656 --> 00:54:01.576
Or are you in a –

963
00:54:03.017 --> 00:54:03.697
Are you in a Jeep?

964
00:54:03.797 --> 00:54:05.498
No offense to Jeep.

965
00:54:05.518 --> 00:54:07.718
The way you feel, where you want to feel every...

966
00:54:07.778 --> 00:54:10.198
I mean, maybe that's part of the point of the Jeep.

967
00:54:10.238 --> 00:54:13.679
But a Jeep would not make a good qubit controller.

968
00:54:13.999 --> 00:54:14.159
Right.

969
00:54:14.199 --> 00:54:15.980
A Rolls Royce might or a Bentley might.

970
00:54:16.060 --> 00:54:19.980
Because that's what they optimize for, is a smooth luxury riding experience.

971
00:54:20.000 --> 00:54:20.220
Yeah.

972
00:54:20.320 --> 00:54:28.482
And so for a lot of these solid state qubits, that means you got to operate at 10 millikelvin above absolute zero, which is colder than outer space.

973
00:54:28.542 --> 00:54:30.443
Outer space is at like three Kelvin.

974
00:54:30.523 --> 00:54:32.643
This is an order of magnitude, if not more,

975
00:54:33.263 --> 00:54:59.441
much colder than outside like outer space and this is where you have to operate the computer so it's like okay you're gonna create this environment at scale to get a million qubits and you're gonna do it at an order of magnitude cooler than deep space yes okay and then the other challenge is in order to operate my qubit i gotta send in electricity or stuff stuff right to like move it around like whether it's lasers or we'll get into that well that better not heat up

976
00:55:00.868 --> 00:55:01.828
the computer.

977
00:55:02.028 --> 00:55:02.289
Right.

978
00:55:02.449 --> 00:55:02.789
Right.

979
00:55:02.849 --> 00:55:07.651
So that's a challenge that is going to affect how well you can scale stuff.

980
00:55:07.711 --> 00:55:07.991
Yes.

981
00:55:08.431 --> 00:55:08.791
Okay.

982
00:55:08.831 --> 00:55:14.273
And if you've ever seen a picture of a quantum computer, you've probably seen like those giant steampunk golden chandeliers.

983
00:55:14.573 --> 00:55:15.133
Yes.

984
00:55:15.274 --> 00:55:17.294
With the wires coming down and things like that.

985
00:55:17.494 --> 00:55:18.055
Yes.

986
00:55:18.355 --> 00:55:23.937
All of that is the, well, the infrastructure of a lot of it is the dilution refrigerator.

987
00:55:23.957 --> 00:55:24.097
Right.

988
00:55:24.317 --> 00:55:33.202
Where you're using helium, a mixture of helium-3 and helium-4, to get down to that base temperature of tens of millikelvin.

989
00:55:33.842 --> 00:55:34.943
Okay?

990
00:55:35.003 --> 00:55:40.706
Who knew being a quantum computer architect was similar to being a butcher who needs to keep their beef frozen?

991
00:55:41.046 --> 00:55:42.587
Yeah, effectively.

992
00:55:42.627 --> 00:55:43.908
Managing refrigeration.

993
00:55:43.968 --> 00:55:45.269
Managing refrigeration, dude.

994
00:55:45.389 --> 00:55:50.892
I have so many horror stories about dilution refrigerators, and that is for another time, let's just say.

995
00:55:51.152 --> 00:55:51.712
But...

996
00:55:53.509 --> 00:55:54.750
The point is you got to keep it cold.

997
00:55:54.770 --> 00:55:54.950
Yeah.

998
00:55:55.391 --> 00:55:55.631
Okay.

999
00:55:56.351 --> 00:56:00.794
So that's why we got to freeze these things to that cold.

1000
00:56:00.934 --> 00:56:02.155
And it better be frozen.

1001
00:56:02.275 --> 00:56:03.436
Which is non-trivial.

1002
00:56:03.656 --> 00:56:04.557
That is non-trivial.

1003
00:56:04.737 --> 00:56:05.037
Okay.

1004
00:56:05.097 --> 00:56:06.398
And that's going to come in later.

1005
00:56:06.738 --> 00:56:06.959
Okay.

1006
00:56:07.219 --> 00:56:08.980
The other thing is how big is the thing going to be?

1007
00:56:09.240 --> 00:56:09.420
Yeah.

1008
00:56:09.500 --> 00:56:09.681
Right.

1009
00:56:09.741 --> 00:56:12.262
The whole if I want a million cubits, how big is it going to be?

1010
00:56:12.282 --> 00:56:14.104
That's a question that you need to ask.

1011
00:56:14.224 --> 00:56:16.105
How much power are you going to need?

1012
00:56:16.671 --> 00:56:18.914
If you've got a bunch of fridges, you're going to need a bunch of power.

1013
00:56:18.934 --> 00:56:20.396
You're going to need a bunch of helium.

1014
00:56:21.016 --> 00:56:22.739
There's not a lot of helium-3 out there.

1015
00:56:22.759 --> 00:56:23.880
There's a lot of helium-4.

1016
00:56:24.481 --> 00:56:27.364
There's not a lot of helium-3 out there in the world.

1017
00:56:27.524 --> 00:56:32.711
And we're not yet bringing it back from the lunar surface to Earth, which is also expensive.

1018
00:56:32.731 --> 00:56:32.851
Yeah.

1019
00:56:32.871 --> 00:56:33.872
Yeah, that would also be it.

1020
00:56:34.172 --> 00:56:34.552
Right?

1021
00:56:34.612 --> 00:56:36.814
That's not a solution for scalability.

1022
00:56:37.114 --> 00:56:37.314
Right?

1023
00:56:37.354 --> 00:56:39.316
At that point, just put a quantum computer on the moon.

1024
00:56:39.516 --> 00:56:40.637
Are you serious?

1025
00:56:40.837 --> 00:56:44.359
We're seeing the same issue with AI where it's like, oh, we want to do, you know, whatever.

1026
00:56:44.379 --> 00:56:49.903
But it's like, okay, but the power is the limiting factor more than compute is.

1027
00:56:50.504 --> 00:56:51.364
And it's the same issue.

1028
00:56:51.725 --> 00:56:52.125
Exactly.

1029
00:56:52.145 --> 00:56:55.207
And then finally, it would be like, how are you going to manufacture this thing at scale?

1030
00:56:55.287 --> 00:56:55.507
Yeah.

1031
00:56:55.687 --> 00:56:56.328
Okay?

1032
00:56:56.488 --> 00:56:57.969
So those are the three criteria.

1033
00:56:58.029 --> 00:57:01.952
Qubit quality, qubit control, and then scalability and economics.

1034
00:57:02.597 --> 00:57:08.070
Okay, and with that, now let's get into our first leading modality.

1035
00:57:08.470 --> 00:57:11.297
Okay, this would be our Manchester City, let's say.

1036
00:57:12.148 --> 00:57:18.009
Okay, so with that in mind, let's start with our first big modality, superconducting qubits.

1037
00:57:18.069 --> 00:57:22.130
And let's analyze superconducting qubits using the FFP criteria.

1038
00:57:22.851 --> 00:57:24.951
Superconducting qubits have made a name for themselves.

1039
00:57:24.991 --> 00:57:27.552
These are the big players, Google, IBM, Rigetti Computing.

1040
00:57:27.932 --> 00:57:29.712
They had the big quantum supremacy.

1041
00:57:31.153 --> 00:57:34.853
This is the Willow chip that you see on there, on that hand.

1042
00:57:35.814 --> 00:57:36.894
So what is the qubit itself?

1043
00:57:36.914 --> 00:57:37.074
Okay.

1044
00:57:39.047 --> 00:57:42.488
A qubit has to be a two-state system that can be in a quantum thingy.

1045
00:57:42.508 --> 00:57:43.249
Yes, yes.

1046
00:57:43.809 --> 00:57:47.691
It's effectively a fancy LC circuit, an inductor and a capacitor.

1047
00:57:48.731 --> 00:57:51.452
From classical electronics, we visited this a lot.

1048
00:57:51.792 --> 00:57:55.594
An LC circuit is effectively an electronic pendulum of sorts.

1049
00:57:56.094 --> 00:57:58.995
The inductor gets charged, then it gets discharged.

1050
00:57:59.035 --> 00:58:02.156
During that time, the capacitor gets charged and then discharged.

1051
00:58:02.177 --> 00:58:08.259
So you have this back and forth where the energy is moving from the inductor into the capacitor, into the inductor, into the capacitor.

1052
00:58:08.935 --> 00:58:14.519
Um, and this becomes a harmonic oscillator is what we call it in physics.

1053
00:58:14.559 --> 00:58:20.283
When you've got like a oscillating system that just obeys, you know, a sine wave.

1054
00:58:22.836 --> 00:58:24.918
Which is what we're seeing in this bottom left.

1055
00:58:25.078 --> 00:58:27.460
Yeah, that's the current.

1056
00:58:27.520 --> 00:58:31.323
The current is going one way, then it's going the other way, then it's going one way, then it's going the other way.

1057
00:58:32.044 --> 00:58:33.285
You can also track the voltage.

1058
00:58:33.765 --> 00:58:38.229
Whatever variable you want to track, it's going to look like a sine wave.

1059
00:58:38.249 --> 00:58:39.410
It's going to have a harmonic.

1060
00:58:39.530 --> 00:58:39.750
Okay.

1061
00:58:40.070 --> 00:58:41.991
Now this is a classical harmonic oscillator.

1062
00:58:42.151 --> 00:58:42.371
Yes.

1063
00:58:42.791 --> 00:58:49.374
If I take this harmonic oscillator and I cool it down, I put it inside a dilution refrigerator, then everything becomes quantum.

1064
00:58:49.714 --> 00:58:49.934
Okay.

1065
00:58:49.974 --> 00:58:51.995
Everything is actually quantum at the end of the day.

1066
00:58:52.015 --> 00:58:52.975
It's just classical.

1067
00:58:52.995 --> 00:58:56.796
There's enough temperature and there's enough modes that, you know, it obeys classical mechanics.

1068
00:58:57.117 --> 00:59:00.818
But if you cool it down enough, you're going to start entering quantum mechanics level.

1069
00:59:01.478 --> 00:59:08.500
And for those who have taken undergraduate quantum mechanics, there's a famous photo in the Griffiths textbook of a cat going up a ladder.

1070
00:59:09.000 --> 00:59:16.941
These are the ladder states of a quantum harmonic oscillator, where each rung of the ladder is a different state that your quantum harmonic oscillator can be in.

1071
00:59:17.281 --> 00:59:20.922
Crucially, the rungs of the ladder are equally spaced.

1072
00:59:21.462 --> 00:59:24.023
And the spacing is h-bar omega.

1073
00:59:24.183 --> 00:59:26.383
H-bar is Planck's constant divided by 2 pi.

1074
00:59:26.763 --> 00:59:30.164
Omega is the resonant frequency of your harmonic oscillator.

1075
00:59:31.620 --> 00:59:35.863
The problem here is that all of the rungs are equally spaced.

1076
00:59:36.143 --> 00:59:36.423
Okay.

1077
00:59:36.643 --> 00:59:36.883
Okay?

1078
00:59:37.824 --> 00:59:50.231
One of the questions with how good is your qubit, one of the questions that comes up with that question, how good is your qubit, is it really a two-state system that's isolated?

1079
00:59:51.177 --> 00:59:54.818
Or can I accidentally go and access some other spot?

1080
00:59:54.858 --> 00:59:57.199
Is there noise in the system?

1081
00:59:57.279 --> 01:00:01.740
Yeah, is there noise such that I leave my computational basis, is what they call it.

1082
01:00:02.000 --> 01:00:04.661
I've got a 0 and a 1, and I want to stay within the 0 and 1.

1083
01:00:04.761 --> 01:00:07.261
I don't want to go to 2 or 3, right?

1084
01:00:07.441 --> 01:00:09.742
Because qubits, bit 2.

1085
01:00:11.142 --> 01:00:17.464
But if there's equal rungs on the ladder, and let's say I poke it with enough energy to go from 0 to 1,

1086
01:00:18.444 --> 01:00:24.128
I could also poke it with enough energy to go from zero to two because the spacing is equal.

1087
01:00:24.668 --> 01:00:27.570
Or if I'm at one and I want to get down to zero, I could poke it.

1088
01:00:27.770 --> 01:00:28.470
It could go to two.

1089
01:00:29.191 --> 01:00:33.874
And this comes to the idea of we have these systems at this very low temperature.

1090
01:00:34.394 --> 01:00:40.738
If it was at a higher temperature, for example, would that be the equivalent of this poking where it could go from a zero to a two?

1091
01:00:40.878 --> 01:00:41.598
Yeah.

1092
01:00:41.918 --> 01:00:43.539
That's one way that it could do it.

1093
01:00:44.680 --> 01:01:06.358
practically do this yes one way but actually what what's worse is even if that's even even if you're at a low enough temperature there's something called stimulated emission of radiation that's the ser in laser okay um and so you can literally go from like one to two even though you wanted to go from one to zero and there's no temperature effect okay if the if the states are equally uh

1094
01:01:07.454 --> 01:01:09.315
the rungs are equally spaced, right?

1095
01:01:09.455 --> 01:01:14.879
The photon could just be like, oh, I'm just going to absorb this instead of absorbing and then emitting two.

1096
01:01:14.899 --> 01:01:16.060
And now I'm at state two.

1097
01:01:16.360 --> 01:01:22.864
So you got to do some finickiness to remove that equalness in the ladder.

1098
01:01:23.364 --> 01:01:32.090
Because the point there is the equalness allows the easy transition from these states, and you basically want to make it so that the zero and one and one and zero is equal.

1099
01:01:32.470 --> 01:01:34.631
But every other state transition is harder.

1100
01:01:34.751 --> 01:01:36.251
Yeah, it's like not equal.

1101
01:01:36.291 --> 01:01:37.571
It's like something different.

1102
01:01:37.651 --> 01:01:38.692
Yeah, something different.

1103
01:01:38.712 --> 01:01:39.532
It's something different.

1104
01:01:39.632 --> 01:01:43.993
So that I can very precisely control my transitions from 0 to 1 and back.

1105
01:01:44.393 --> 01:01:48.474
But I can also very precisely say that I'm not going to go elsewhere.

1106
01:01:48.574 --> 01:01:50.334
Yeah, that makes sense.

1107
01:01:50.454 --> 01:01:52.355
So in order to fix that...

1108
01:01:53.567 --> 01:01:59.098
They replace the inductor with a Josephson junction back to our Josephson junction.

1109
01:01:59.720 --> 01:02:00.120
That's right.

1110
01:02:00.421 --> 01:02:03.146
So last year we had a great episode.

1111
01:02:04.362 --> 01:02:17.228
about the Nobel Prize winners in physics, Michel DeVere, John Clark, and John Martinez, they showed for the first time that you could have macroscopic quantum tunneling in a Josephson Junction at Berkeley.

1112
01:02:17.488 --> 01:02:20.749
It was a really good episode, and I encourage people to watch it.

1113
01:02:22.130 --> 01:02:29.853
This sort of started that idea of using a Josephson Junction, cooling it down, and using that as part of your qubit.

1114
01:02:30.854 --> 01:02:33.035
So now, if we replace a Josephson Junction

1115
01:02:34.563 --> 01:02:36.383
in place of the inductor, what happens?

1116
01:02:36.463 --> 01:02:43.445
Well, instead of a perfect quantum harmonic oscillator, which is on the left, that's a parabola.

1117
01:02:43.525 --> 01:02:45.905
That's the potential of a parabola.

1118
01:02:46.485 --> 01:02:50.026
And on the right-hand side, instead of a parabola, we introduce a cosine.

1119
01:02:50.626 --> 01:02:51.787
It's the bottom of a cosine.

1120
01:02:51.827 --> 01:02:58.308
Now, the bottom of a cosine, crucially, kind of looks like a parabola, but the farther out you get, it diverges from a parabola.

1121
01:02:58.328 --> 01:02:58.488
Right.

1122
01:02:59.396 --> 01:03:07.163
What that means is your 0 to 1 has a certain spacing, but the other ones have different spacing.

1123
01:03:07.424 --> 01:03:13.169
And it continues to diverge farther away from the parabola.

1124
01:03:13.189 --> 01:03:13.950
Yeah, yeah, yeah.

1125
01:03:13.990 --> 01:03:15.852
In a parabola, it would be exactly spaced.

1126
01:03:16.012 --> 01:03:17.013
Right, right.

1127
01:03:17.033 --> 01:03:18.254
Just because of how the math works out.

1128
01:03:18.274 --> 01:03:19.095
Right, right, right, right.

1129
01:03:19.115 --> 01:03:24.580
But with a cosine, now you've got different spacings, and now I can very exactly, hopefully...

1130
01:03:25.400 --> 01:03:29.241
toggle between 0 and 1, and I don't have to worry about going into 2 and things like that.

1131
01:03:29.861 --> 01:03:32.802
So this would be a great qubit, right?

1132
01:03:32.922 --> 01:03:35.902
If exactly I could always do 0 to 1 and so on and so forth.

1133
01:03:36.042 --> 01:03:36.923
Fair enough.

1134
01:03:37.223 --> 01:03:38.363
So that's what we're doing.

1135
01:03:38.383 --> 01:03:41.044
We're going to replace the inductor with a Josephson junction.

1136
01:03:41.324 --> 01:03:42.864
And this is what it looks like in practice.

1137
01:03:43.324 --> 01:03:45.505
So this is called an X-mon.

1138
01:03:45.685 --> 01:03:49.746
These qubits are called trans-mons, the ones that Google and IBM uses at least.

1139
01:03:50.326 --> 01:03:52.966
And under a microscope, this is what it looks like.

1140
01:03:52.986 --> 01:03:54.827
So on the left-hand side, we've got like a cross.

1141
01:03:55.727 --> 01:03:57.688
The big cross is the giant capacitor.

1142
01:03:58.268 --> 01:03:58.508
Okay?

1143
01:03:58.808 --> 01:04:01.229
And zooming in there, there's the Josephson junction.

1144
01:04:03.490 --> 01:04:07.452
And effectively, this is your qubit.

1145
01:04:08.812 --> 01:04:10.893
There's a little circuit that runs inside.

1146
01:04:10.993 --> 01:04:18.076
It's superconducting, which means that if you let it run, it's just going to keep running, which is nice, because you want your qubit to sort of stay qubit-y.

1147
01:04:18.796 --> 01:04:19.777
And...

1148
01:04:20.760 --> 01:04:29.166
That interference device, the SQUID, that's called a superconducting quantum interference device, it's creating the 0 and 1.

1149
01:04:29.186 --> 01:04:31.628
This entire ensemble is creating your 0 and 1.

1150
01:04:32.048 --> 01:04:33.149
Now, how do you talk to it?

1151
01:04:33.729 --> 01:04:34.430
This is my qubit.

1152
01:04:34.450 --> 01:04:35.390
This is the substrate.

1153
01:04:35.790 --> 01:04:45.057
This can hold my 0, which is one state of the circuit, and the 1, which is another state of the circuit, the sort of a little bit higher frequency.

1154
01:04:45.077 --> 01:04:45.177
Okay.

1155
01:04:45.477 --> 01:04:46.738
Or, yeah, higher frequency.

1156
01:04:47.339 --> 01:04:55.206
And would you say that this is speaking to the qubit quality variable in the criterion?

1157
01:04:55.246 --> 01:04:55.646
Yeah, yeah.

1158
01:04:55.666 --> 01:04:57.448
I'm trying to define the qubit itself.

1159
01:04:57.468 --> 01:04:57.869
Right, right.

1160
01:04:57.889 --> 01:05:01.852
So, like, by defining it, now we can then speak to this.

1161
01:05:01.952 --> 01:05:03.514
We can then judge it against the criterion.

1162
01:05:03.534 --> 01:05:04.054
Yeah, yeah, yeah.

1163
01:05:04.074 --> 01:05:07.437
We understand its structure and what it's actually doing.

1164
01:05:07.477 --> 01:05:07.818
Made of.

1165
01:05:08.038 --> 01:05:08.338
Made of.

1166
01:05:08.358 --> 01:05:08.498
Yeah.

1167
01:05:08.839 --> 01:05:10.380
And what the zero and the one state is.

1168
01:05:10.400 --> 01:05:10.560
Yeah.

1169
01:05:11.641 --> 01:05:17.403
So then we can begin to, as we go through this process, ask the questions about quality control.

1170
01:05:17.443 --> 01:05:17.864
Exactly.

1171
01:05:18.184 --> 01:05:19.364
And scalability.

1172
01:05:19.724 --> 01:05:20.164
Yeah.

1173
01:05:20.184 --> 01:05:25.727
And the one more thing before we start judging with the criteria is I'd like to talk about how do you actually talk to the thing?

1174
01:05:25.987 --> 01:05:26.227
Yes.

1175
01:05:26.287 --> 01:05:26.507
Right?

1176
01:05:27.248 --> 01:05:32.392
Once we define the qubit and how we talk about it or how we talk to it, then we can get into the criteria.

1177
01:05:32.612 --> 01:05:36.855
So that's going to be the format of all of these sort of audits, so to speak.

1178
01:05:37.436 --> 01:05:38.536
So how do we talk to the thing?

1179
01:05:38.937 --> 01:05:41.319
We use microwaves in the gigahertz range.

1180
01:05:41.579 --> 01:05:42.540
So here we've got a chip.

1181
01:05:43.492 --> 01:05:45.273
That has four Transmons qubits.

1182
01:05:45.673 --> 01:05:47.393
Those are on the bottom there, those four.

1183
01:05:47.893 --> 01:05:52.775
They are connected to a driveline on the bottom.

1184
01:05:53.515 --> 01:05:59.477
Those are little lines that send in microwave pulses to change your qubit from a zero to a one.

1185
01:06:00.137 --> 01:06:02.138
And then you see the top squiggles.

1186
01:06:02.938 --> 01:06:04.699
Those are your readout resonators.

1187
01:06:05.139 --> 01:06:05.379
Okay?

1188
01:06:05.820 --> 01:06:11.743
And if the qubit is in one state or the other, it's going to resonate with a microwave that's inside that.

1189
01:06:12.223 --> 01:06:16.766
You can imagine like, you know in fiber optics, fiber optics like carry light through it, right?

1190
01:06:16.786 --> 01:06:19.848
This is a fancy mini fiber optic thingy.

1191
01:06:20.208 --> 01:06:20.468
Okay?

1192
01:06:20.688 --> 01:06:23.190
That's going to hold a microwave inside.

1193
01:06:23.570 --> 01:06:30.254
And if the microwave is exactly the right frequency, it's going to resonate with each of these little squiggly waveguides.

1194
01:06:30.754 --> 01:06:30.995
Okay.

1195
01:06:31.575 --> 01:06:35.301
And so basically where we read is in these readout resonators.

1196
01:06:35.381 --> 01:06:36.863
Yeah.

1197
01:06:37.063 --> 01:06:41.270
If the qubit is in one state or the other, the readout resonator is going to resonate.

1198
01:06:41.330 --> 01:06:45.456
And then my line up top is going to go back up to my electronics and tell me.

1199
01:06:45.816 --> 01:06:48.438
What state is each of the four in?

1200
01:06:48.538 --> 01:06:49.719
Because we have four qubits.

1201
01:06:50.480 --> 01:06:58.687
And so we want, and then we have each of these resonator readout, like basically lines that connect to our piece that's going to send it back up to us.

1202
01:06:58.707 --> 01:07:02.350
So we can independently read each of the four qubits.

1203
01:07:02.410 --> 01:07:04.131
And so this is a four qubit.

1204
01:07:04.812 --> 01:07:10.796
It's a transmon computer, a four qubit superconducting circuits computer.

1205
01:07:10.876 --> 01:07:19.882
And the way they talk to each other is just through cross capacitance, meaning like if there's a circuit over here and a circuit over here, they're going to affect each other using electric fields.

1206
01:07:19.922 --> 01:07:20.783
Just by proximity.

1207
01:07:20.823 --> 01:07:22.684
Just by proximity, straight up.

1208
01:07:23.285 --> 01:07:26.367
And I mean, so does that kind of make sense?

1209
01:07:26.387 --> 01:07:28.928
The driveline sort of tells you how to poke it.

1210
01:07:29.509 --> 01:07:31.050
The qubits are in the middle.

1211
01:07:31.090 --> 01:07:32.611
They can be in either a zero or a one.

1212
01:07:33.031 --> 01:07:38.853
And the resonator that's up top is going to let you read what the state it's in.

1213
01:07:38.933 --> 01:07:41.935
So there's my, you know, initialize, manipulate, readout.

1214
01:07:42.015 --> 01:07:42.195
Yes.

1215
01:07:42.435 --> 01:07:42.675
Okay?

1216
01:07:42.995 --> 01:07:44.736
It's just going from bottom to top.

1217
01:07:44.836 --> 01:07:45.516
Makes total sense.

1218
01:07:45.956 --> 01:07:47.056
Okay.

1219
01:07:47.897 --> 01:07:50.558
Now, we know about how the quantum computer works.

1220
01:07:50.578 --> 01:07:51.758
Now let's do the audit, right?

1221
01:07:51.798 --> 01:07:53.839
How does it hold up to the FFP criteria?

1222
01:07:54.239 --> 01:07:55.260
Well, what are the strengths?

1223
01:07:56.220 --> 01:07:58.401
The strengths are that...

1224
01:07:59.848 --> 01:08:06.155
superconducting qubits have very fast operations, 10 to 30 nanoseconds.

1225
01:08:06.175 --> 01:08:12.382
You know, those rotations on the block sphere that I was showing earlier, those gates, they can happen within 10 to 30 nanoseconds.

1226
01:08:12.542 --> 01:08:12.843
That's fast.

1227
01:08:12.863 --> 01:08:13.003
Okay.

1228
01:08:13.263 --> 01:08:14.144
That's very fast.

1229
01:08:14.264 --> 01:08:19.831
And crucially, if you have two qubit gates, it's maybe a little bit longer, like 60 nanoseconds.

1230
01:08:20.291 --> 01:08:20.471
But,

1231
01:08:21.252 --> 01:08:25.596
The coherence time, how long a qubit remembers itself, is quite long.

1232
01:08:25.716 --> 01:08:26.317
Yeah, that's nice.

1233
01:08:26.337 --> 01:08:26.497
Okay?

1234
01:08:26.777 --> 01:08:27.397
It's nice.

1235
01:08:27.438 --> 01:08:36.485
We actually covered a paper by Princeton earlier in this podcast season where they described a qubit with one millisecond.

1236
01:08:37.406 --> 01:09:03.344
of coherence time which is fantastic which is fantastic compared to nanoseconds yes if you're doing tens of nanoseconds to to like move stuff around if the thing can remember for a whole millisecond that's there's 10 to the 6 nanoseconds there's a million nanoseconds in a millisecond just to give you the like you've got a lot of time to poke around with it right and basically make sure you like can read what's happening right like the the coherence time effectively is how long do

1237
01:09:04.725 --> 01:09:05.305
And manipulate.

1238
01:09:05.325 --> 01:09:09.947
And manipulate before the system collapses and you have to start again.

1239
01:09:10.027 --> 01:09:10.968
Yes, exactly.

1240
01:09:12.008 --> 01:09:22.292
And that Princeton paper used tantalum, which is – I always find it hilarious to like, you know, in high school when we learned about the periodic table –

1241
01:09:23.178 --> 01:09:28.961
There were all these elements that we were just like, who uses tantalum?

1242
01:09:29.501 --> 01:09:33.563
But yeah, in quantum computing industry, there's so many exotic materials like tantalum.

1243
01:09:34.103 --> 01:09:42.947
We're going to get into ytterbium later, which is, you know, I didn't think, when I was in high school, I was like, why would I need to know about ytterbium?

1244
01:09:42.987 --> 01:09:44.168
There's good reasons for it, right?

1245
01:09:44.648 --> 01:09:46.629
So, okay, that's a strength.

1246
01:09:46.789 --> 01:09:48.070
The gate speeds are really fast.

1247
01:09:48.210 --> 01:09:48.450
Yeah.

1248
01:09:48.570 --> 01:09:52.257
The coherence time is pretty long compared to the gate speeds.

1249
01:09:52.577 --> 01:09:54.741
So you can implement an algorithm pretty quickly.

1250
01:09:55.783 --> 01:09:56.845
What are the negatives?

1251
01:09:57.907 --> 01:10:00.592
Well, one, remember I told you about that

1252
01:10:01.882 --> 01:10:06.465
that anharmonicity, meaning it's drifting away from harmonic.

1253
01:10:06.525 --> 01:10:08.546
Harmonic meaning parabola.

1254
01:10:08.986 --> 01:10:16.030
But I've introduced this cosine term that sort of gets rid of that degeneracy in the energy spacing.

1255
01:10:16.090 --> 01:10:18.431
So only 0 and 1 is a certain energy spacing.

1256
01:10:18.771 --> 01:10:21.133
The other ones are not that energy spacing.

1257
01:10:21.173 --> 01:10:28.777
So when I want to talk to 0 and 1, I send a microwave pulse that is exactly that energy, and I can toggle between 0 and 1.

1258
01:10:29.417 --> 01:10:31.438
And this is the ladder rung distancing.

1259
01:10:31.498 --> 01:10:34.300
And it's like you want to be able to know which rungs of the ladder you're on.

1260
01:10:34.420 --> 01:10:40.063
And that's why you want there to be a difference between the different distance between 0 and 1 and others.

1261
01:10:40.143 --> 01:10:40.543
And others.

1262
01:10:40.743 --> 01:10:41.304
However.

1263
01:10:42.044 --> 01:10:43.125
Yeah, there's a problem.

1264
01:10:43.245 --> 01:10:43.525
Okay.

1265
01:10:43.625 --> 01:10:48.848
There's a tiny problem, which is as I'm the gates, like how I manipulate this qubit.

1266
01:10:50.495 --> 01:10:53.556
Depends on microwaves getting sent in, right?

1267
01:10:54.017 --> 01:10:56.978
Now, if I could send in a pure tone, right?

1268
01:10:57.478 --> 01:11:02.921
Like, you know, those tuning forks that have a pure tone.

1269
01:11:03.861 --> 01:11:09.524
If I could send in a pure tone at exactly that frequency, that's the difference between the zero and a one, then I'd be fine.

1270
01:11:10.184 --> 01:11:15.887
But a pure tone necessarily means a very long time to send that frequency.

1271
01:11:17.248 --> 01:11:17.488
Right?

1272
01:11:17.588 --> 01:11:17.928
Yes.

1273
01:11:18.427 --> 01:11:26.254
Now, as I start squishing the frequency, right, I start doing a beep or a boop or a boop.

1274
01:11:27.435 --> 01:11:29.577
That's a very... Mr. Acapella, everybody.

1275
01:11:31.418 --> 01:11:33.280
But notice over there, right?

1276
01:11:33.540 --> 01:11:38.384
What I did was I was trying to access different notes in sound, but I was trying to make it very short.

1277
01:11:38.645 --> 01:11:38.885
Yeah.

1278
01:11:39.706 --> 01:11:52.489
Now, if you were to take that microphone, that sound readout, and then you were to ask some computer algorithm, what are the frequencies in when Krishna did beep versus boop?

1279
01:11:54.091 --> 01:11:59.897
There's going to be the main frequency, which is the note that I was trying to get to, but there's also going to be off frequencies.

1280
01:12:00.258 --> 01:12:00.518
Okay?

1281
01:12:00.778 --> 01:12:07.105
There's going to be other frequencies in there because I'm trying to squish all of the notes into a very short time scale.

1282
01:12:07.406 --> 01:12:10.829
This is actually straight up Heisenberg uncertainty principle.

1283
01:12:11.210 --> 01:12:14.994
There is a tradeoff between your accuracy and frequency.

1284
01:12:15.467 --> 01:12:16.928
and your accuracy in time.

1285
01:12:17.349 --> 01:12:22.493
So if I make the time window smaller, the frequency bandwidth gets larger.

1286
01:12:22.953 --> 01:12:23.934
That's a problem.

1287
01:12:24.795 --> 01:12:34.883
Because now, if I'm trying to only toggle between 0 and 1, but I'm sending these really short pulses, there's a chance that I toggle the other frequency.

1288
01:12:35.003 --> 01:12:39.627
Like, there's a chance that some of the other frequencies have made it in into that short pulse.

1289
01:12:40.780 --> 01:12:43.303
And so now I might be accessing the other states.

1290
01:12:43.743 --> 01:12:45.325
Yes, this tracks.

1291
01:12:45.365 --> 01:12:58.258
The idea is because we need to communicate at a very fast rate because of other limitations of the system, the accuracy by which we can read between the zero and one.

1292
01:12:58.899 --> 01:12:59.941
it kind of gets fuzzy.

1293
01:12:59.981 --> 01:13:02.824
It necessarily needs to get fuzzy because we're trying to communicate so quickly.

1294
01:13:02.845 --> 01:13:03.065
Yes.

1295
01:13:03.145 --> 01:13:04.667
So it's like, this is like, there's a trade-off.

1296
01:13:04.687 --> 01:13:04.847
Right.

1297
01:13:04.867 --> 01:13:05.508
It's one or the other.

1298
01:13:05.608 --> 01:13:05.829
Yeah.

1299
01:13:05.909 --> 01:13:06.509
You can't have both.

1300
01:13:06.730 --> 01:13:06.930
Yeah.

1301
01:13:06.950 --> 01:13:13.038
You can't have very fast and then high fidelity, like understanding of the frequency that you're sitting.

1302
01:13:13.198 --> 01:13:15.722
Like it's, if you do it very fast, Yeah.

1303
01:13:15.862 --> 01:13:16.443
Then, yeah.

1304
01:13:16.703 --> 01:13:18.044
The frequency is a little fuzzy.

1305
01:13:18.164 --> 01:13:18.384
Yeah.

1306
01:13:18.704 --> 01:13:18.864
Yeah.

1307
01:13:18.944 --> 01:13:20.385
And so you need to control it really well.

1308
01:13:20.425 --> 01:13:22.407
And just to show how much you want to control it, right?

1309
01:13:22.707 --> 01:13:27.290
The thing, the difference between these states, the zero and the one, is at a gigahertz range.

1310
01:13:27.390 --> 01:13:27.690
Okay.

1311
01:13:27.870 --> 01:13:28.110
Okay.

1312
01:13:28.130 --> 01:13:28.951
That's 10 to the nine.

1313
01:13:29.151 --> 01:13:29.331
Yeah.

1314
01:13:29.751 --> 01:13:34.654
But the difference between, so the difference between zero and one is a gigahertz.

1315
01:13:35.034 --> 01:13:39.177
The difference between one and two is also in that gigahertz range.

1316
01:13:39.537 --> 01:13:44.100
It's different from the first one by only like hundreds of megahertz.

1317
01:13:44.120 --> 01:13:44.320
Mm-hmm.

1318
01:13:45.738 --> 01:13:45.958
Right?

1319
01:13:46.019 --> 01:13:47.320
Yeah, yeah, yeah.

1320
01:13:47.340 --> 01:13:50.584
So the two rungs of the ladder are not all that different.

1321
01:13:50.785 --> 01:13:51.546
Yeah, yeah.

1322
01:13:51.766 --> 01:13:55.891
In terms of how we're able to actually read the difference based on what we just talked about.

1323
01:13:55.931 --> 01:13:56.372
Exactly.

1324
01:13:56.432 --> 01:13:57.934
So that's a problem, right?

1325
01:13:58.234 --> 01:14:02.019
And the other thing is something called microscopic defect coupling.

1326
01:14:02.700 --> 01:14:08.923
Effectively, there are these two-level systems in any interface, and this is a problem in sort of any solid-state electronics.

1327
01:14:08.943 --> 01:14:12.325
Whenever you have interfaces, like, for example, the Josephson Junction.

1328
01:14:12.605 --> 01:14:18.227
Let's say the Josephson Junction is made out of aluminum with some aluminum oxide in the middle and then aluminum.

1329
01:14:18.608 --> 01:14:24.090
Now, the aluminum and oxygen, they form these bonds, but those bonds can be maybe in one of two states.

1330
01:14:24.651 --> 01:14:26.551
Like, that's the red circle and the pink circle.

1331
01:14:27.292 --> 01:14:29.433
If the energy between those two states...

1332
01:14:30.521 --> 01:14:39.643
is about the same as your qubits, 0 and 1, then when I'm trying to talk to the qubit, sometimes instead of talking to the qubit, I will talk to this bond.

1333
01:14:40.343 --> 01:14:42.824
And the bond will toggle between one bond and the other.

1334
01:14:43.644 --> 01:14:44.324
And then it's like, ah.

1335
01:14:45.224 --> 01:14:47.625
So it's like you end up reading the substrate rather than the system.

1336
01:14:47.645 --> 01:14:47.965
Yeah, yeah.

1337
01:14:47.985 --> 01:14:49.525
I'm trying to talk to this one thing.

1338
01:14:50.025 --> 01:14:54.946
But as I send my microwave, the microwave is going to spread out because microwaves have a large wavelength.

1339
01:14:54.966 --> 01:14:55.706
They're going to spread out.

1340
01:14:55.746 --> 01:14:58.287
And maybe it'll poke this other thing.

1341
01:14:59.044 --> 01:15:04.211
And it just happens to be in the right state and phase to send a response back.

1342
01:15:04.271 --> 01:15:15.765
And so the point here being, from cubic quality, we have gate speed is great, but the...

1343
01:15:16.961 --> 01:15:19.783
inability to distinguish between zero and one in other states.

1344
01:15:20.443 --> 01:15:20.643
Yeah.

1345
01:15:21.003 --> 01:15:24.085
And it might be interacting with your substrate.

1346
01:15:24.125 --> 01:15:25.326
Yeah, yeah, some other stuff.

1347
01:15:25.706 --> 01:15:26.446
It's problematic.

1348
01:15:26.546 --> 01:15:27.607
It's problematic, right?

1349
01:15:27.987 --> 01:15:28.227
Okay.

1350
01:15:28.667 --> 01:15:29.988
So now that was cubic quality.

1351
01:15:30.008 --> 01:15:31.049
Now let's talk about control.

1352
01:15:31.549 --> 01:15:35.671
Now the strength is that you've got direct microwave interfacing.

1353
01:15:35.972 --> 01:15:39.133
Okay, the energy splittings are firmly in the microwave domain.

1354
01:15:39.433 --> 01:15:45.737
And that means that control and readout can leverage modern telecom and radio frequency equipment.

1355
01:15:46.077 --> 01:15:46.277
Right?

1356
01:15:46.338 --> 01:15:47.800
We're really good at radar.

1357
01:15:47.840 --> 01:15:49.542
We're really good at radio and things like that.

1358
01:15:50.063 --> 01:15:50.944
The negatives, though...

1359
01:15:51.800 --> 01:15:53.401
One is planar connectivity.

1360
01:15:53.461 --> 01:15:58.102
The transmons rely on nearest neighbor 2D coupling.

1361
01:15:58.422 --> 01:16:06.825
So the types of error codes that you can kind of implement here are limited by the connectivity of your chip.

1362
01:16:07.486 --> 01:16:10.847
Meaning only certain types of connectivity can we really effectively use this for.

1363
01:16:11.067 --> 01:16:13.968
And this is honestly like, I mean, it kind of makes sense.

1364
01:16:14.308 --> 01:16:16.749
This is something that a lot of things have to deal with.

1365
01:16:16.789 --> 01:16:17.469
That's totally fine.

1366
01:16:18.029 --> 01:16:19.970
The one that I want to kind of focus on

1367
01:16:21.169 --> 01:16:25.070
is crosstalk and frequency crowding.

1368
01:16:25.390 --> 01:16:29.771
Okay, here's the photo again of our four-qubit computer.

1369
01:16:29.791 --> 01:16:31.692
I want you to notice something.

1370
01:16:32.512 --> 01:16:36.853
You see those resonant readout cavities, the squiggles?

1371
01:16:38.214 --> 01:16:39.074
They're all different.

1372
01:16:40.853 --> 01:16:41.273
You see them?

1373
01:16:41.553 --> 01:16:41.753
Yeah.

1374
01:16:41.773 --> 01:16:45.534
The one on the left is like taller, like it's like thinner.

1375
01:16:45.694 --> 01:16:46.015
Yeah.

1376
01:16:46.255 --> 01:16:48.715
And the one on the right is larger.

1377
01:16:48.755 --> 01:16:49.256
Yeah, yeah, yeah.

1378
01:16:49.596 --> 01:16:49.816
Right?

1379
01:16:50.216 --> 01:16:50.496
Yeah.

1380
01:16:50.836 --> 01:16:51.096
Okay.

1381
01:16:51.636 --> 01:16:53.277
There's a very good reason for that.

1382
01:16:54.017 --> 01:17:03.820
The reason is, suppose I send in a microwave at a certain frequency, at a certain energy difference to the one on the left.

1383
01:17:03.840 --> 01:17:04.000
Yeah.

1384
01:17:06.183 --> 01:17:18.177
To make sure that that microwave doesn't bleed out and talk to the other ones, each of the microwaves, each of the transmon qubits need to have a unique resonant frequency.

1385
01:17:19.618 --> 01:17:20.299
Does that make sense?

1386
01:17:20.359 --> 01:17:20.679
It does.

1387
01:17:20.759 --> 01:17:21.239
No, it does.

1388
01:17:21.300 --> 01:17:21.440
Right?

1389
01:17:21.460 --> 01:17:27.485
Because if I want to talk to this guy with one language, the other ones better not be able to understand me.

1390
01:17:27.705 --> 01:17:29.426
It's like a walkie-talkie with different channels.

1391
01:17:29.666 --> 01:17:30.227
Exactly.

1392
01:17:30.267 --> 01:17:32.469
You need different channels, otherwise everyone's going to... Yeah.

1393
01:17:32.729 --> 01:17:34.210
Or straight up the radio, right?

1394
01:17:34.310 --> 01:17:41.236
There's a reason why 89.9 is KPCC and 91.5 is KUSC for classical.

1395
01:17:41.376 --> 01:17:42.077
Right.

1396
01:17:42.177 --> 01:17:43.858
For those who live in Los Angeles, right?

1397
01:17:44.539 --> 01:17:46.100
And I think there's a 0.2 megahertz...

1398
01:17:48.842 --> 01:18:12.354
like gap between all of our radio stations right because when i tune to one i better hear the one that i want to listen to yeah right and not the other ones and so you need them to have they're not trying to all listen to yeah and there's the problem with like am because am can bounce from the atmosphere sometimes when you like drive out you know you'll get like these you'll get like the the talk radio from sacramento and also and so and so

1399
01:18:12.694 --> 01:18:18.839
Depending on where you are in the mountain, you'll switch between someone talking in Sacramento or someone talking in Los Angeles, right?

1400
01:18:19.039 --> 01:18:19.699
Yes.

1401
01:18:19.980 --> 01:18:20.760
But that's the idea.

1402
01:18:21.061 --> 01:18:21.561
That makes sense.

1403
01:18:21.581 --> 01:18:29.247
Now, this creates a challenge because you've got a certain bandwidth where you can put all of your unique frequencies, right?

1404
01:18:29.287 --> 01:18:32.229
Like for radio, for example, I think it goes from what?

1405
01:18:32.289 --> 01:18:33.470
Let's say 87 to 106, right?

1406
01:18:33.490 --> 01:18:34.351
That's a numbers game.

1407
01:18:34.371 --> 01:18:34.491
Yeah.

1408
01:18:43.343 --> 01:18:43.944
That I can put.

1409
01:18:43.964 --> 01:18:45.405
I can't put more.

1410
01:18:46.266 --> 01:18:48.088
Because you need at least that two-meganets gap.

1411
01:18:48.368 --> 01:18:48.548
Yeah.

1412
01:18:48.848 --> 01:18:51.831
So this idea is called frequency crowding.

1413
01:18:51.851 --> 01:18:53.012
Crowding and crosstalk.

1414
01:18:53.072 --> 01:18:53.593
I get you.

1415
01:18:53.653 --> 01:18:55.835
Now, there's ways to fix it.

1416
01:18:55.855 --> 01:19:02.842
For example, you could have like a flux biasing that you pump some voltage into each of the qubits and then that raises or lowers the...

1417
01:19:03.202 --> 01:19:10.146
the resonant frequency, but then that introduces like one over F noise and all sorts, because you're not introducing more electronics into the system.

1418
01:19:10.186 --> 01:19:10.386
Right.

1419
01:19:10.406 --> 01:19:11.386
So there's ways around it.

1420
01:19:11.426 --> 01:19:16.849
I'm just saying this is like a kind of a mathematical thing that you need to worry about.

1421
01:19:16.869 --> 01:19:17.169
Yeah.

1422
01:19:17.209 --> 01:19:17.389
Right.

1423
01:19:17.730 --> 01:19:17.990
Okay.

1424
01:19:18.330 --> 01:19:22.812
Which foreshadowing some other systems might not have to, might not have to.

1425
01:19:22.932 --> 01:19:23.152
Right.

1426
01:19:24.273 --> 01:19:27.014
So finally, let's get into the scalability and electronics.

1427
01:19:27.274 --> 01:19:27.415
Yep.

1428
01:19:28.315 --> 01:19:29.476
There's a wiring problem.

1429
01:19:30.516 --> 01:19:31.617
This is the Google willow.

1430
01:19:32.847 --> 01:19:39.549
computer, all of those lines that you're seeing, those are coaxial cables that bring the microwaves down to the qubit.

1431
01:19:40.249 --> 01:19:40.469
Okay?

1432
01:19:40.829 --> 01:19:41.990
That's not the refrigeration.

1433
01:19:42.010 --> 01:19:44.030
The refrigeration is mostly in the metal.

1434
01:19:44.630 --> 01:19:46.411
All of those lines are microwave lines.

1435
01:19:46.691 --> 01:19:47.491
Oh, that's interesting.

1436
01:19:47.891 --> 01:19:48.131
Okay?

1437
01:19:48.231 --> 01:19:48.511
Okay.

1438
01:19:48.531 --> 01:19:50.992
That's the microwaves that are talking to your qubits.

1439
01:19:51.072 --> 01:19:51.932
Yeah.

1440
01:19:52.032 --> 01:19:53.633
And a lot of these lines are fat.

1441
01:19:54.053 --> 01:20:01.195
They're semi-rigid coaxial cables made out of stainless steel or superconducting niobium.

1442
01:20:01.975 --> 01:20:06.078
And they deliver some resonant frequency to these individual qubits.

1443
01:20:06.659 --> 01:20:09.060
And this is the stuff that goes all the way down to the qubits.

1444
01:20:09.441 --> 01:20:16.065
So there's a wiring problem in terms of there's a bunch of wires, and I don't know how many more wires I can fit into this thing.

1445
01:20:16.366 --> 01:20:16.626
Yeah.

1446
01:20:17.046 --> 01:20:17.306
Okay?

1447
01:20:18.587 --> 01:20:19.948
And we live in a wireless world.

1448
01:20:19.968 --> 01:20:20.349
No, I'm kidding.

1449
01:20:21.309 --> 01:20:22.370
Effectively.

1450
01:20:22.450 --> 01:20:28.455
Now, the other problem is the qubit itself is at tens of millikelvin.

1451
01:20:28.515 --> 01:20:28.675
Yeah.

1452
01:20:28.695 --> 01:20:28.895
Yeah.

1453
01:20:29.814 --> 01:20:30.034
Right?

1454
01:20:30.814 --> 01:20:34.035
Now, if... And this is what a dilution refrigerator looks like.

1455
01:20:34.195 --> 01:20:43.218
A dilution refrigerator you can think of as a Russian nesting doll of big, and then you use the big as a heat dump for... At the top.

1456
01:20:43.438 --> 01:20:43.918
At the top.

1457
01:20:44.278 --> 01:20:46.919
At the top, you have like a 55 Kelvin, right?

1458
01:20:46.959 --> 01:20:48.719
I mean, at the top, I guess you have room temperature.

1459
01:20:48.759 --> 01:20:50.740
That's where the heat is getting dumped.

1460
01:20:50.800 --> 01:20:54.161
You use the room temperature to dump heat and get down to 55 Kelvin.

1461
01:20:54.241 --> 01:20:54.381
Right?

1462
01:20:55.561 --> 01:21:01.783
And then you use another stage to get down to 4 Kelvin to dump heat to the 55 Kelvin, which dumps heat back to room.

1463
01:21:01.803 --> 01:21:04.925
So you have this Russian nesting doll of like cooling stages, right?

1464
01:21:06.125 --> 01:21:11.507
All the way down at the very end is the 10 millikelvin stage, which is where your qubits sit.

1465
01:21:12.201 --> 01:21:19.404
But all of your control lines, the microwaves and everything, have to go all the way down to 10 millikelvin in order to talk to your qubits.

1466
01:21:19.824 --> 01:21:25.367
That means you're heating up that 10 millikelvin stage with a bunch of microwaves.

1467
01:21:25.767 --> 01:21:25.967
Yeah.

1468
01:21:26.571 --> 01:21:27.412
And there was a lot of them.

1469
01:21:27.672 --> 01:21:28.593
And there was a lot of them.

1470
01:21:29.014 --> 01:21:31.997
So the question is, how many can I get in this?

1471
01:21:32.197 --> 01:21:39.985
There's some limiting capacity based on the need to be able to control the levels of heat at some very, very low level.

1472
01:21:40.105 --> 01:21:40.346
Yes.

1473
01:21:40.426 --> 01:21:42.628
And so there's some upper limit, theoretically.

1474
01:21:42.848 --> 01:21:43.149
Exactly.

1475
01:21:43.169 --> 01:21:46.732
Like how many microwave lines can you actually put there before it becomes...

1476
01:21:47.573 --> 01:22:16.770
there's no room there's no room there's no room and there's no more cooling capacity right right um and the other thing is each of those transpons that you saw earlier they're at the scale of a millimeter one millimeter it's actually quite big it's quite large it's quite big um if you're trying to fit a million of these things it's not going to fit in a single dilution refrigerator yeah okay so one of the so there's there's there's a bunch of problems here um the cubit itself is too big there's too many wires that are going down um

1477
01:22:18.102 --> 01:22:20.583
And there's a frequency crowding, right?

1478
01:22:20.663 --> 01:22:24.745
For a single sort of chip, there's not that many that I can do mathematically even.

1479
01:22:25.786 --> 01:22:31.768
So in each dilution refrigerator, I can't actually fit that many qubits.

1480
01:22:32.609 --> 01:22:33.289
What I'd have to do

1481
01:22:34.678 --> 01:22:38.439
is get a bunch of dilution refrigerators and rig them up.

1482
01:22:38.479 --> 01:22:43.361
Like a server rack where you have multiple individual servers into this rack system.

1483
01:22:43.481 --> 01:22:43.921
Exactly.

1484
01:22:44.281 --> 01:22:46.982
And actually, IBM is kind of working on that.

1485
01:22:47.122 --> 01:22:47.382
Okay.

1486
01:22:47.502 --> 01:22:50.003
They've made a modular dilution refrigerator.

1487
01:22:50.023 --> 01:22:51.404
This came out very, very recently.

1488
01:22:51.484 --> 01:22:51.664
Okay.

1489
01:22:51.684 --> 01:22:51.784
Okay.

1490
01:22:52.885 --> 01:23:10.221
where they're showing that you can take a bunch of single dilution refrigerators, fit everything inside of it, and then these quantum fridges, they're 200 times colder than deep space, but that's just every dilution refrigerator, so that's part of that headline, and could pave way for fault-tolerant quantum computing, because you've got a bunch of these, you connect them together.

1491
01:23:10.501 --> 01:23:14.705
Now the communication between one dilution refrigerator and the next better be very, very good.

1492
01:23:14.945 --> 01:23:15.706
That's another layer.

1493
01:23:15.706 --> 01:23:17.348
That's another layer that I have to worry about.

1494
01:23:17.428 --> 01:23:24.996
Because now you're creating this individual component now in a larger system that was already its own system.

1495
01:23:25.817 --> 01:23:26.357
Yeah.

1496
01:23:26.518 --> 01:23:31.923
And effectively, if I rig a bunch of these dilution refrigerators up, I'm going to need like a data center.

1497
01:23:33.178 --> 01:23:33.998
type of warehouse.

1498
01:23:34.018 --> 01:23:34.198
Yeah.

1499
01:23:34.358 --> 01:23:34.518
Yeah.

1500
01:23:34.919 --> 01:23:37.599
With a bunch of dilution refrigerators all rigged up.

1501
01:23:37.799 --> 01:23:37.960
Yeah.

1502
01:23:38.420 --> 01:23:39.920
And we already can't get data centers.

1503
01:23:39.980 --> 01:23:40.160
Right.

1504
01:23:40.300 --> 01:23:41.441
We already hate data centers.

1505
01:23:41.481 --> 01:23:41.661
Right.

1506
01:23:42.201 --> 01:23:42.361
Right.

1507
01:23:42.621 --> 01:23:46.302
And we're using that as a, as a, as a structure and architectural and structural point.

1508
01:23:46.322 --> 01:23:46.502
Yes.

1509
01:23:46.642 --> 01:23:48.103
It's not literally a data center.

1510
01:23:48.143 --> 01:23:48.843
No, no.

1511
01:23:48.923 --> 01:23:50.203
It's a quantum, I guess it's a quantum.

1512
01:23:50.263 --> 01:23:55.325
I don't know if you, but the point is you're talking about the scale and the size of power, water, water,

1513
01:23:55.785 --> 01:24:24.206
physical space that's necessary to actually have this helium three where are you going to get the helium three i will say it looks really nice it does the marketing photo looks great right and like just for one of these there's going to be a lot of helium three right and now you want to scale this to multiple right where are you going there's questions there's resource constraints on the architecture there's questions that need to be answered yes okay and so now um and you can do these estimates other people have done these estimates for a thousand plus qubits um and

1514
01:24:25.007 --> 01:24:26.528
For a thousand plus logical qubits.

1515
01:24:26.588 --> 01:24:28.148
Which is not the million we talked about earlier.

1516
01:24:28.268 --> 01:24:28.448
No.

1517
01:24:28.689 --> 01:24:29.309
It's just a thousand.

1518
01:24:29.329 --> 01:24:33.610
A thousand logical qubits, you need ten million physical qubits of these transplants.

1519
01:24:33.751 --> 01:24:34.371
Okay.

1520
01:24:34.771 --> 01:24:38.893
And you need like ten million dollars, right?

1521
01:24:38.953 --> 01:24:43.534
For a million, you're talking like billions of dollars for a single quantum computer.

1522
01:24:44.555 --> 01:24:44.815
Yeah.

1523
01:24:46.354 --> 01:24:47.416
Yeah, that's tough.

1524
01:24:47.576 --> 01:24:48.358
It's tough, it's tough.

1525
01:24:48.699 --> 01:24:50.663
Billions of dollars for a single computer?

1526
01:24:50.683 --> 01:24:53.168
It's not gonna, it's not, right?

1527
01:24:53.228 --> 01:24:55.412
And the footprint is the size of a warehouse, um...

1528
01:24:56.321 --> 01:24:56.521
Yeah.

1529
01:24:56.801 --> 01:24:58.262
So let's look at the final verdict.

1530
01:24:58.342 --> 01:24:59.042
Final verdict.

1531
01:24:59.082 --> 01:25:01.683
The FFP criteria for superconducting circuits.

1532
01:25:02.163 --> 01:25:04.064
Cupid quality, I'm going to say, is 5 out of 10.

1533
01:25:04.124 --> 01:25:05.625
Cupid control is 5 out of 10.

1534
01:25:05.745 --> 01:25:08.005
Scalability and economics, 1 out of 10.

1535
01:25:08.346 --> 01:25:10.126
For a total of 11 out of 30.

1536
01:25:11.247 --> 01:25:15.628
The quantitative criteria about which we judge this is, of course, proprietary.

1537
01:25:15.668 --> 01:25:16.889
Proprietary.

1538
01:25:17.969 --> 01:25:21.731
Proprietary FFP IP.

1539
01:25:22.031 --> 01:25:24.312
If you claim that I made these numbers up,

1540
01:25:25.372 --> 01:25:48.450
uh i will sue you i guess that's that's what uh you are making claims against our proprietary uh trade secrets yeah yeah yeah if you if you claim that i mean you'll see how these numbers get when we go to a neutral neutral atoms let's just say that um but 11 out of 30 not not great really struggled in the scalability and economics category which goes back to

1541
01:25:48.970 --> 01:25:57.698
This whole point we talked about earlier about electric relays and vacuum tubes, yes, they could operate as transistors.

1542
01:25:58.158 --> 01:26:03.463
However, if you want an iPhone, you cannot have an iPhone made of vacuum tubes.

1543
01:26:04.264 --> 01:26:14.373
And ultimately, what is going to matter in these spaces because of the way we engage with technology in general and the use cases for how people want to use this stuff is,

1544
01:26:14.762 --> 01:26:24.988
is that the economics and the scalability matters just as much as the fundamentals, which is where a lot of the energy has been put so far.

1545
01:26:25.548 --> 01:26:33.433
And then the problem is you go down a route, and then you've invested so much in that route that then you get this inertia of like, well...

1546
01:26:34.469 --> 01:26:35.570
we have to commit to this.

1547
01:26:35.770 --> 01:26:41.073
So we have to make, we have to like make the economics fit into this path.

1548
01:26:41.113 --> 01:26:42.614
We've already spent billions of dollars on.

1549
01:26:42.814 --> 01:26:46.876
And this is where you get a lot of the tension in these corporate environments of like, well, we can't like pivot.

1550
01:26:47.076 --> 01:26:47.256
Yeah.

1551
01:26:47.537 --> 01:26:54.400
And like, to be clear, I mean, we're not trying to make an iPhone out of quantum computers, but we're trying to have a lot of quantum computers.

1552
01:26:54.480 --> 01:26:57.622
And if a single quantum computer is billions of dollars, that's not great.

1553
01:26:58.183 --> 01:26:59.984
We, we, where's the helium three going to come from?

1554
01:27:00.004 --> 01:27:00.144
Yeah.

1555
01:27:00.564 --> 01:27:00.724
Yeah.

1556
01:27:00.744 --> 01:27:00.884
Yeah.

1557
01:27:00.904 --> 01:27:01.084
Yeah.

1558
01:27:01.444 --> 01:27:01.725
Exactly.

1559
01:27:01.745 --> 01:27:03.346
I mean, it's just like, there's just like functional.

1560
01:27:03.386 --> 01:27:03.526
Yeah.

1561
01:27:03.546 --> 01:27:03.646
Yeah.

1562
01:27:04.246 --> 01:27:05.086
Even if you just had one.

1563
01:27:05.246 --> 01:27:05.446
Yeah.

1564
01:27:05.746 --> 01:27:09.888
And like you can't make this in a TSMC, for example.

1565
01:27:10.068 --> 01:27:10.248
Right.

1566
01:27:10.568 --> 01:27:11.108
And things like that.

1567
01:27:11.228 --> 01:27:11.688
So, okay.

1568
01:27:12.088 --> 01:27:24.412
So that was... Like it's been great for the quantum computing industry because it's been able to get to like this intermediate scale quantum computer where they can show quantum supremacy and things like that.

1569
01:27:24.772 --> 01:27:25.812
I just don't think it's the future.

1570
01:27:26.112 --> 01:27:26.513
That's fair.

1571
01:27:26.833 --> 01:27:29.213
Superconducting qubits, 11 out of 30.

1572
01:27:29.653 --> 01:27:31.214
So next up, trapped ions.

1573
01:27:32.057 --> 01:27:35.819
Quantinuum just had its IPO, $15 billion.

1574
01:27:35.999 --> 01:27:37.740
Quantinuum?

1575
01:27:37.880 --> 01:27:38.840
Yeah, Quantinuum.

1576
01:27:39.061 --> 01:27:40.081
I love that.

1577
01:27:40.221 --> 01:27:41.382
It debuted on the NASDAQ.

1578
01:27:41.522 --> 01:27:42.682
Billion dollar IPO.

1579
01:27:42.802 --> 01:27:44.263
Yeah.

1580
01:27:44.383 --> 01:27:46.564
Another one is IonQ that's based out of Maryland.

1581
01:27:46.584 --> 01:27:48.265
These two companies do trapped ions.

1582
01:27:48.605 --> 01:27:53.148
Lots of UCLA physics people actually are involved with Quantinuum.

1583
01:27:53.168 --> 01:27:59.651
Their chief quantum architect is Anthony Ransford, who told me himself that he's a fan of the podcast.

1584
01:27:59.731 --> 01:28:00.431
Shout out, Anthony.

1585
01:28:00.451 --> 01:28:01.152
Shout out Bruins.

1586
01:28:01.172 --> 01:28:01.812
Bruins Nation.

1587
01:28:01.932 --> 01:28:02.413
Yeah, yeah.

1588
01:28:02.553 --> 01:28:04.455
But you still got to go through the audit.

1589
01:28:04.655 --> 01:28:07.738
Hopefully you still agree to call on the podcast.

1590
01:28:07.758 --> 01:28:08.499
We shall see.

1591
01:28:09.280 --> 01:28:10.842
So what is the qubit?

1592
01:28:11.082 --> 01:28:11.342
Okay.

1593
01:28:11.722 --> 01:28:13.244
Now, this is not a man-made circuit.

1594
01:28:13.444 --> 01:28:16.648
They are using an actual literal atom.

1595
01:28:17.755 --> 01:28:18.416
All right.

1596
01:28:18.656 --> 01:28:22.399
Usually it's something like uterbium or barium.

1597
01:28:22.620 --> 01:28:24.541
What they do, in this case, it's barium, right?

1598
01:28:24.561 --> 01:28:28.105
Barium's got these two electrons on its outer shell.

1599
01:28:28.505 --> 01:28:34.871
You remove one of them, then it becomes a positive ion because now there's more protons in the nucleus than there are electrons around it.

1600
01:28:35.511 --> 01:28:38.374
And now the whole thing has a positive electrical charge.

1601
01:28:38.754 --> 01:28:42.618
Now, because of that charge, you can now move it around using electromagnetic fields.

1602
01:28:44.552 --> 01:28:45.753
There's a key way to do this, though.

1603
01:28:45.773 --> 01:28:47.574
You can't use a static electric field.

1604
01:28:47.874 --> 01:28:55.740
You can't just put a bunch of, like, electrodes at certain voltages and trap them because the ion is going to figure out a way to just, like, shoot out.

1605
01:28:56.101 --> 01:28:58.943
So instead, you have to oscillate the electric fields.

1606
01:28:58.963 --> 01:29:05.808
You can find in one direction and these two other directions, you, like, you know, you go positive, negative, and then you switch from negative, positive.

1607
01:29:06.348 --> 01:29:08.450
And this back and forth...

1608
01:29:09.090 --> 01:29:12.533
is sort of massaging the ions to stay in a certain spot.

1609
01:29:12.893 --> 01:29:19.218
And that is how you confine a bunch of ions in a single location.

1610
01:29:19.258 --> 01:29:20.479
This is called a pall trap.

1611
01:29:20.899 --> 01:29:23.762
And this is basically how we're trying to create the qubit states.

1612
01:29:23.842 --> 01:29:24.822
Yes.

1613
01:29:25.003 --> 01:29:26.584
Well, first you've got to localize it.

1614
01:29:26.684 --> 01:29:27.264
Right, right, right.

1615
01:29:27.284 --> 01:29:29.266
With the transmons, it's like, oh, it's on a circuit.

1616
01:29:29.286 --> 01:29:30.107
It's like right there.

1617
01:29:30.327 --> 01:29:30.507
Right.

1618
01:29:30.727 --> 01:29:30.927
Right.

1619
01:29:30.967 --> 01:29:33.868
But with atoms now I got to put them, I got to keep them in a spot.

1620
01:29:34.368 --> 01:29:39.890
And so the way you keep them in a spot is using this oscillating electromagnetic field that like oscillates at a certain frequency.

1621
01:29:39.970 --> 01:29:45.252
It's funny because before we're talking about oscillation from like the microwaves and how it's coming back to that same idea.

1622
01:29:45.272 --> 01:29:47.853
You have to maintain the state via oscillating somehow.

1623
01:29:48.013 --> 01:29:48.373
Somehow.

1624
01:29:48.453 --> 01:29:49.413
Yeah.

1625
01:29:49.973 --> 01:29:51.474
Harmonic oscillators are everywhere.

1626
01:29:52.134 --> 01:29:54.336
In physics, to be honest.

1627
01:29:54.636 --> 01:29:57.838
So that's how you keep the ion in a certain spot.

1628
01:29:58.259 --> 01:30:06.425
The qubit states, the zero and the one, these are two very specific stable energy levels of the atom's outermost electron.

1629
01:30:06.625 --> 01:30:11.589
We've seen this photo before of the hydrogen hyperfine transition.

1630
01:30:11.989 --> 01:30:17.513
This was sent on the Pioneer probes and the Voyager probes where the electron on the outside of the hydrogen is,

1631
01:30:17.847 --> 01:30:22.371
is either parallel to the spin of the proton or it's anti-parallel to the spin of the proton.

1632
01:30:22.651 --> 01:30:25.573
And the difference between those two is 1420 megahertz.

1633
01:30:26.814 --> 01:30:36.522
And that set the time on the pioneer record that we sent out for the aliens if they wanted to decipher where we're from and how to locate Earth and things like that.

1634
01:30:36.802 --> 01:30:38.403
This is called a hyperfine transition.

1635
01:30:38.443 --> 01:30:43.267
It's when the electron is parallel to the nuclear spin versus opposite the nuclear spin.

1636
01:30:44.503 --> 01:30:49.727
The trapped ion people, at least in continuum, they're using these two as their zero and one.

1637
01:30:49.987 --> 01:30:50.227
Okay.

1638
01:30:50.427 --> 01:30:50.648
Okay?

1639
01:30:50.908 --> 01:30:51.828
That's their zero and one.

1640
01:30:51.889 --> 01:30:57.252
And the way you interact between them is using lasers.

1641
01:30:58.073 --> 01:30:58.954
Laser beam.

1642
01:30:59.274 --> 01:30:59.514
Right?

1643
01:30:59.674 --> 01:31:04.938
And the energy scale between these guys is about 12 gigahertz.

1644
01:31:04.958 --> 01:31:06.679
So it's in the microwave frequencies.

1645
01:31:06.860 --> 01:31:07.440
Okay.

1646
01:31:07.700 --> 01:31:10.682
And that temperature is equivalent to about 600 millikelvin.

1647
01:31:11.163 --> 01:31:11.263
Okay.

1648
01:31:11.283 --> 01:31:11.443
Okay.

1649
01:31:11.543 --> 01:31:17.326
Okay, so the temperature difference or the energy difference between your zero and one in this case is less than a Kelvin.

1650
01:31:17.606 --> 01:31:18.347
Okay.

1651
01:31:18.447 --> 01:31:23.710
It's larger than the superconducting but still less than a Kelvin.

1652
01:31:23.750 --> 01:31:24.350
Yeah.

1653
01:31:24.430 --> 01:31:27.312
My point is here, this stuff still operates at room temperature though.

1654
01:31:27.912 --> 01:31:28.732
The question is why.

1655
01:31:29.433 --> 01:31:31.694
It's because you suspend it in a vacuum.

1656
01:31:32.294 --> 01:31:35.315
If you put it in a vacuum, then nothing is interacting with it.

1657
01:31:35.495 --> 01:31:40.137
There's no atoms that are jiggling around that are poking it, hopefully, if the vacuum is good enough.

1658
01:31:40.637 --> 01:31:46.140
And all of the electrons—I mean, sorry, all of the photons—because remember, at any given temperature—

1659
01:31:46.640 --> 01:31:54.523
There's not just degrees of freedom with the atoms that are moving around, but also there's degrees of freedom with photons and the electromagnetic field.

1660
01:31:54.863 --> 01:32:03.966
And so in this room itself, for example, in our body, there are photons that are jiggling around at around infrared because we are at about 300 Kelvin.

1661
01:32:05.046 --> 01:32:11.190
Now, there's going to be a bunch of photons that are poking this ion thing, right, at 300 Kelvin.

1662
01:32:11.430 --> 01:32:14.372
It just so happens, though, that a lot of those photons are in the infrared.

1663
01:32:15.133 --> 01:32:20.496
And those infrared photons are very different from the energy gap between the zero and the one.

1664
01:32:20.536 --> 01:32:21.317
So they just sort of...

1665
01:32:22.497 --> 01:32:23.098
Coast through.

1666
01:32:23.298 --> 01:32:24.839
Coming back to our rungs of the ladder.

1667
01:32:25.179 --> 01:32:28.742
They're not at the range that matters for us in what we're looking at.

1668
01:32:28.762 --> 01:32:28.922
Exactly.

1669
01:32:28.942 --> 01:32:29.542
The rungs of the ladder.

1670
01:32:29.562 --> 01:32:30.022
Exactly.

1671
01:32:30.042 --> 01:32:31.023
Yeah.

1672
01:32:31.103 --> 01:32:32.944
That was a question that I had when I was researching this.

1673
01:32:32.984 --> 01:32:34.305
It's like, okay, fine.

1674
01:32:35.046 --> 01:32:39.309
It's a vacuum, but you have an ambient heat bath of photons.

1675
01:32:39.789 --> 01:32:41.450
How come that doesn't destroy you?

1676
01:32:41.470 --> 01:32:44.052
Well, it's because these guys just aren't sensitive to that.

1677
01:32:44.332 --> 01:32:48.395
The rungs of the ladder are very different from the poking that's happening, right?

1678
01:32:48.535 --> 01:32:48.735
Mm-hmm.

1679
01:32:49.246 --> 01:32:51.828
Okay, so how do you talk to them?

1680
01:32:52.028 --> 01:32:53.029
Well, you use lasers.

1681
01:32:53.409 --> 01:32:58.053
You line up a chain of these glowing ions in a trap so that you've got chains of ions.

1682
01:32:58.393 --> 01:33:03.497
Single qubit gates are done using precisely tuned laser beams on the individual ions.

1683
01:33:04.377 --> 01:33:07.019
And then two qubit gates are where it gets kind of wild.

1684
01:33:07.099 --> 01:33:07.440
Okay.

1685
01:33:07.460 --> 01:33:07.720
Okay?

1686
01:33:08.080 --> 01:33:13.985
So two qubit gates are done using effectively sound waves in your ion mesh.

1687
01:33:14.684 --> 01:33:15.004
Okay.

1688
01:33:15.124 --> 01:33:16.024
Okay?

1689
01:33:16.264 --> 01:33:17.765
These things are charged, right?

1690
01:33:17.805 --> 01:33:23.146
Which means if I move one guy, it's positively charged, so it's going to repel everything else.

1691
01:33:23.166 --> 01:33:25.006
Because we've removed the two outer shell.

1692
01:33:25.026 --> 01:33:25.686
One, just one of them.

1693
01:33:25.787 --> 01:33:26.667
One of the outer shell electrons.

1694
01:33:26.687 --> 01:33:27.787
So it's just a barium plus.

1695
01:33:27.907 --> 01:33:29.067
Okay.

1696
01:33:29.247 --> 01:33:31.888
And we use the remaining outer shell as the hyperfine, right?

1697
01:33:31.968 --> 01:33:32.588
Got it.

1698
01:33:32.728 --> 01:33:38.889
But if I move one of these barium atoms, that's going to cause a Coulomb repulsion, an electrostatic repulsion on the other one.

1699
01:33:38.909 --> 01:33:40.550
Because, you know, like charges...

1700
01:33:43.374 --> 01:33:44.154
Do not attract.

1701
01:33:44.635 --> 01:33:45.035
Repel.

1702
01:33:45.415 --> 01:33:46.415
That's the word.

1703
01:33:46.675 --> 01:33:49.296
And so if I move one of these guys, that's going to move one of these guys.

1704
01:33:49.316 --> 01:33:50.517
That's going to move one of these guys, right?

1705
01:33:50.777 --> 01:33:57.839
And those phonon modes, those sound waves, are how you start entangling and doing two-qubit gates.

1706
01:33:58.099 --> 01:33:59.100
It's kind of interesting, right?

1707
01:33:59.280 --> 01:34:00.300
That's interesting.

1708
01:34:01.653 --> 01:34:02.494
That's interesting.

1709
01:34:02.514 --> 01:34:02.774
Yeah.

1710
01:34:02.954 --> 01:34:03.534
Yeah.

1711
01:34:04.715 --> 01:34:05.595
I thought it was pretty cool.

1712
01:34:06.076 --> 01:34:10.198
Because now it's just another means of – is this now – I'm trying to think about it.

1713
01:34:10.218 --> 01:34:11.459
This is how we measure.

1714
01:34:11.879 --> 01:34:12.519
This is the measure.

1715
01:34:12.860 --> 01:34:15.841
No, this is how we do two-cubit gates.

1716
01:34:15.861 --> 01:34:20.744
So how we entangle them, how we get them to talk to one another is using sound waves.

1717
01:34:20.784 --> 01:34:23.646
We read them out and measure them using the lasers again.

1718
01:34:23.726 --> 01:34:23.906
Okay.

1719
01:34:24.086 --> 01:34:24.426
Got it.

1720
01:34:24.546 --> 01:34:25.407
It's effectively imaging.

1721
01:34:25.627 --> 01:34:47.695
got it it's like you you poke it with and you try to see is it in a this state or this state that's interesting but the the the way in which we're having them entangle or interact is via sound with sound waves that's interesting that's cool yeah that's cool that's quite nice yeah it's called the cool points mulmur sorenson gate okay okay okay um and and that's it's the jiggling

1722
01:34:48.795 --> 01:34:51.517
of the sound waves between these ions that's actually doing this.

1723
01:34:51.537 --> 01:34:51.897
So, okay.

1724
01:34:52.137 --> 01:34:54.919
How does this hold up with the FFP criteria?

1725
01:34:54.959 --> 01:34:57.741
And this is a chip that shows right in the center.

1726
01:34:57.761 --> 01:34:58.701
You've got this line.

1727
01:34:58.761 --> 01:34:59.742
Yeah, yeah, yeah.

1728
01:34:59.802 --> 01:35:00.382
Right in the middle.

1729
01:35:00.582 --> 01:35:01.603
Okay, okay, okay.

1730
01:35:01.703 --> 01:35:04.304
Okay, so how does it hold up with the FFP criteria?

1731
01:35:04.345 --> 01:35:05.005
The strength...

1732
01:35:07.533 --> 01:35:12.939
This is mother nature's ultimate qubit in some sense, because every single qubit is identical.

1733
01:35:13.520 --> 01:35:16.143
Before with the superconducting thing, you know, you got to manufacture it.

1734
01:35:16.223 --> 01:35:19.867
Each thing is going to be different kind of by design because you want the resonant frequencies to be different.

1735
01:35:19.907 --> 01:35:21.609
Here, everything is exactly equal.

1736
01:35:21.649 --> 01:35:26.575
And as long as I can point my laser accurately, I can be like, okay, talk to this guy.

1737
01:35:26.615 --> 01:35:27.536
Now talk to this guy.

1738
01:35:27.956 --> 01:35:29.018
and so on and so forth, right?

1739
01:35:29.038 --> 01:35:30.900
So every single qubit is actually the same.

1740
01:35:31.181 --> 01:35:34.705
There's no, like, two-level system causing headaches that are in the background.

1741
01:35:35.546 --> 01:35:40.193
The other thing is the coherence time is pretty ridiculous on these guys.

1742
01:35:40.673 --> 01:35:44.398
How long, again, coherence time being how long it remembers...

1743
01:35:44.999 --> 01:36:10.266
the zero and one so you can then yeah chain manipulate or read yeah and i ultimately mess with mess with it ultimately we want as long of a coherence time as possible yeah this thing can get to 10 hours okay that's right so i i take an ion yeah i put it in the zero state i come back several hours later and it'll still be in the zero state that's that's quite nice that's quite nice that's quite nice right okay

1744
01:36:10.966 --> 01:36:12.967
No, that's quite nice.

1745
01:36:13.427 --> 01:36:13.988
That's a big deal.

1746
01:36:14.008 --> 01:36:18.770
Because that's a totally different category than what we were talking about with superconducting qubits.

1747
01:36:18.850 --> 01:36:19.030
Yeah.

1748
01:36:19.270 --> 01:36:20.651
In terms of coherence time.

1749
01:36:20.811 --> 01:36:21.251
Yeah, yeah.

1750
01:36:21.331 --> 01:36:22.651
They were happy with a millisecond.

1751
01:36:22.711 --> 01:36:23.232
Right.

1752
01:36:23.272 --> 01:36:24.152
We're just in...

1753
01:36:24.452 --> 01:36:24.832
Right.

1754
01:36:24.872 --> 01:36:25.733
Here we're doing hours.

1755
01:36:25.813 --> 01:36:26.073
Okay.

1756
01:36:26.353 --> 01:36:26.613
But...

1757
01:36:26.973 --> 01:36:27.254
Okay.

1758
01:36:27.714 --> 01:36:28.354
There's a caveat.

1759
01:36:28.574 --> 01:36:28.874
Okay.

1760
01:36:29.695 --> 01:36:33.977
With the superconducting, a millisecond was great because the gate times were nanoseconds.

1761
01:36:34.017 --> 01:36:34.537
Yeah, right.

1762
01:36:34.557 --> 01:36:34.677
Right?

1763
01:36:35.942 --> 01:36:40.305
Here, the gates are really, really slow because we're using sound.

1764
01:36:40.445 --> 01:36:43.047
Yeah, and sound waves are... Sound waves are kind of slow.

1765
01:36:43.147 --> 01:36:48.250
And there's actually an upper limit to how fast you can do these gates.

1766
01:36:48.691 --> 01:36:51.633
And it has to do with how fast the pall traps are going.

1767
01:36:51.953 --> 01:37:00.398
Like, you know the thing I was showing you earlier with the electromagnetic fields, like kind of maintaining these ions in a geographic position?

1768
01:37:00.979 --> 01:37:04.061
Those things are creating like a sort of bulk

1769
01:37:04.575 --> 01:37:07.076
That is like, it's really a saddle, you know, those saddles.

1770
01:37:07.376 --> 01:37:09.497
It's like creating a saddle that is rotating around.

1771
01:37:09.937 --> 01:37:16.479
The rotation rate of that saddle is kind of like an upper limit on how fast my gates can be.

1772
01:37:17.459 --> 01:37:20.180
Because the ions are moving around in that saddle, right?

1773
01:37:20.220 --> 01:37:25.562
If you try to like, it's kind of like, imagine if you're like two people on a swing, right?

1774
01:37:25.942 --> 01:37:27.523
And you're swinging back and forth.

1775
01:37:28.325 --> 01:37:32.227
That swinging back and forth, let's say, is the electromagnetic saddle that is keeping you there.

1776
01:37:32.507 --> 01:37:38.189
But you're trying to communicate using the beam that is connecting you in the playground.

1777
01:37:38.389 --> 01:37:44.692
You're trying to communicate with the person next to you based on how you can vibrate the beam above you that is holding you together.

1778
01:37:45.532 --> 01:37:47.733
There's going to be a limit to how fast you can make it.

1779
01:37:48.293 --> 01:37:53.615
And part of then what this means is because that gate time is now slower.

1780
01:37:53.815 --> 01:37:54.036
Yeah.

1781
01:37:54.656 --> 01:37:54.816
Yeah.

1782
01:37:56.465 --> 01:37:59.367
Even though our coherence time is very long, you can just do less.

1783
01:37:59.728 --> 01:37:59.908
Yeah.

1784
01:38:01.249 --> 01:38:01.489
Right?

1785
01:38:01.689 --> 01:38:02.169
Yeah.

1786
01:38:02.209 --> 01:38:02.490
Yeah.

1787
01:38:02.530 --> 01:38:08.374
Like the coherence time is way longer, but you can do less with the same amount of just physical time in the lab.

1788
01:38:08.394 --> 01:38:08.614
Right.

1789
01:38:08.654 --> 01:38:08.854
Right.

1790
01:38:09.135 --> 01:38:09.335
Right.

1791
01:38:09.415 --> 01:38:09.615
Right.

1792
01:38:09.775 --> 01:38:09.955
Right.

1793
01:38:10.295 --> 01:38:15.900
So just because you would ideally want a longer coherence time and a really short gate time.

1794
01:38:15.960 --> 01:38:16.200
Yes.

1795
01:38:16.320 --> 01:38:22.164
And so we're like, yeah, we have long coherence time, but we're now having a much longer from as compared to superconducting qubits, longer gate time.

1796
01:38:22.184 --> 01:38:25.267
So you can just basically cycle to do stuff less frequently.

1797
01:38:25.587 --> 01:38:25.827
Is that...

1798
01:38:26.007 --> 01:38:26.628
Yeah, yeah, yeah.

1799
01:38:26.648 --> 01:38:31.473
So it's like the scale of the quantum circuit that you're trying to implement might actually be the same.

1800
01:38:31.573 --> 01:38:32.234
Right, yeah.

1801
01:38:32.274 --> 01:38:33.895
Because both of the things have scaled.

1802
01:38:33.975 --> 01:38:35.917
Right, exactly, exactly, exactly.

1803
01:38:35.937 --> 01:38:36.138
Okay.

1804
01:38:36.198 --> 01:38:38.260
Yeah, yeah, yeah.

1805
01:38:38.300 --> 01:38:40.102
So that's one of the caveats, right?

1806
01:38:40.642 --> 01:38:40.762
Okay.

1807
01:38:41.957 --> 01:38:43.758
Now, what about the control?

1808
01:38:43.858 --> 01:38:46.078
So we did cubit quality and sort of gate quality.

1809
01:38:46.538 --> 01:38:48.199
Now, the control, there is a strength here.

1810
01:38:48.679 --> 01:38:50.379
You can get all-to-all connectivity.

1811
01:38:51.300 --> 01:38:51.580
Okay?

1812
01:38:52.160 --> 01:38:53.440
You don't have to do nearest neighbor.

1813
01:38:53.740 --> 01:38:58.422
Because what you can do is move around the ion so that any ion can talk to any other ion.

1814
01:38:58.942 --> 01:38:59.122
Right?

1815
01:38:59.502 --> 01:39:03.883
And for Helios from Quantinium, Helios is their latest processor.

1816
01:39:04.363 --> 01:39:05.864
He's also out in Nature.

1817
01:39:05.884 --> 01:39:08.785
They had a nice paper out in Nature.

1818
01:39:08.905 --> 01:39:09.625
Not on the cover, though.

1819
01:39:10.955 --> 01:39:11.615
That was me.

1820
01:39:11.816 --> 01:39:12.276
That was Lester.

1821
01:39:12.296 --> 01:39:13.817
That was me, Anthony.

1822
01:39:13.837 --> 01:39:14.617
That was Lester.

1823
01:39:14.678 --> 01:39:17.139
Anthony's first author on this.

1824
01:39:17.199 --> 01:39:17.960
Congratulations.

1825
01:39:18.100 --> 01:39:19.961
Congratulations.

1826
01:39:20.101 --> 01:39:22.683
So anyways, this is what the cubit chip looks like.

1827
01:39:22.703 --> 01:39:24.584
So on the right-hand side, it's printed out.

1828
01:39:24.624 --> 01:39:25.905
You can see there's like a ring.

1829
01:39:26.906 --> 01:39:31.329
And then there's like a sort of two trains that are going into the ring.

1830
01:39:31.869 --> 01:39:33.290
These are where all the ions sit.

1831
01:39:33.350 --> 01:39:36.092
Okay, the ring is kind of like ring storage.

1832
01:39:36.572 --> 01:39:37.013
And the...

1833
01:39:38.512 --> 01:39:39.413
And that's your memory.

1834
01:39:39.453 --> 01:39:40.733
The ring is your memory.

1835
01:39:40.813 --> 01:39:44.415
And then on the right-hand side where you do the logic is your processor.

1836
01:39:44.435 --> 01:39:46.096
It looks very von Neumann-y.

1837
01:39:46.156 --> 01:39:46.676
Yeah, yeah.

1838
01:39:46.696 --> 01:39:47.977
You know, von Neumann architecture.

1839
01:39:48.037 --> 01:39:50.699
You've got the separation between memory and processing.

1840
01:39:50.739 --> 01:39:51.259
Ring and processor.

1841
01:39:51.279 --> 01:39:52.300
So I thought that was kind of cool.

1842
01:39:52.320 --> 01:39:53.220
That is nice.

1843
01:39:54.000 --> 01:39:56.282
I just think, yeah, the implementation of like...

1844
01:39:56.882 --> 01:40:00.265
there being a separate storage for processing and a separate storage for memory.

1845
01:40:00.485 --> 01:40:03.347
And you can have this kind of memory because your coherence times are so long.

1846
01:40:03.687 --> 01:40:08.971
You can mess with stuff and then just move it into the memory and it'll kind of just remember where it was.

1847
01:40:09.351 --> 01:40:13.234
And what you can do is move stuff around so that there's an interaction zone

1848
01:40:14.532 --> 01:40:16.374
Where you can make the two interact.

1849
01:40:16.414 --> 01:40:18.777
You can put any two ions right next to each other.

1850
01:40:19.117 --> 01:40:22.361
And that's where they get their all-to-all connectivity.

1851
01:40:22.641 --> 01:40:27.888
Now, they out here saying that it's all-to-all connectivity, comma, two at a time.

1852
01:40:29.508 --> 01:40:33.891
Because it's really, you got to put two next to each other, and then you interact those two.

1853
01:40:34.251 --> 01:40:37.293
It's just you can choose any two.

1854
01:40:37.433 --> 01:40:41.075
It is all to all connectivity, but it's two at a time.

1855
01:40:41.636 --> 01:40:42.936
But it's still pretty good.

1856
01:40:44.978 --> 01:40:46.258
So I thought that was really cool.

1857
01:40:46.318 --> 01:40:50.301
And then this is the quantum logic, the processing part of their paper.

1858
01:40:51.382 --> 01:40:56.226
One other really cool thing that I thought of, actually, when I was visiting this.

1859
01:40:56.506 --> 01:40:58.949
So they use barium as their computational qubit, right?

1860
01:40:58.969 --> 01:41:03.973
The barium ion, the hyperfine, so the outer electron being either aligned or not aligned.

1861
01:41:03.993 --> 01:41:05.595
That's your zero and one.

1862
01:41:05.635 --> 01:41:09.438
But if you want to cool this thing down, you still need to cool it down, right?

1863
01:41:09.598 --> 01:41:12.781
Like you still need it to not jiggle around and access.

1864
01:41:13.061 --> 01:41:16.525
Like the ion itself is going to have other states, just like how the superconducting

1865
01:41:17.045 --> 01:41:19.345
qubit had all these twos, threes, and fours.

1866
01:41:19.405 --> 01:41:22.626
The ion itself, the electron could do random other nonsense, right?

1867
01:41:23.106 --> 01:41:28.127
So there's other states that you don't want it to get to, which means you've got to cool even the ion down.

1868
01:41:28.287 --> 01:41:30.807
But you don't want to cool it down by poking it.

1869
01:41:30.967 --> 01:41:32.748
Which is independent of it being in a vacuum.

1870
01:41:32.828 --> 01:41:34.108
Yeah, yeah, yeah.

1871
01:41:34.148 --> 01:41:35.408
That's an independent thing.

1872
01:41:35.648 --> 01:41:38.029
If it's in a vacuum, that means no atom is going to bump into it.

1873
01:41:38.469 --> 01:41:43.630
But there's still, as I said, these photons and things going around, and you don't want it to access all these other spots.

1874
01:41:43.710 --> 01:41:43.850
Yep.

1875
01:41:45.731 --> 01:41:48.654
And the electromagnetic trap is also moving it around, right?

1876
01:41:48.974 --> 01:41:51.396
The little rotating saddle is also moving it around.

1877
01:41:51.436 --> 01:41:52.618
So you've got to be able to cool this thing.

1878
01:41:52.998 --> 01:41:58.964
And when you're moving it around in this ring, in the processor, right, you're physically moving these ions around.

1879
01:41:59.284 --> 01:42:01.306
That's going to introduce heat into the system.

1880
01:42:01.346 --> 01:42:02.587
So you need a way to cool it down.

1881
01:42:02.708 --> 01:42:02.968
Okay.

1882
01:42:03.649 --> 01:42:08.975
But you don't want to poke the barium ion because that would destroy the quantum information.

1883
01:42:08.995 --> 01:42:13.900
So every single barium ion has a partner, uterbium ion, right next to it.

1884
01:42:14.181 --> 01:42:19.367
And what you do is you cool the uterbium ion with a different laser at a different frequency, right?

1885
01:42:19.627 --> 01:42:22.510
And then because the uterbium ion is cooling...

1886
01:42:23.278 --> 01:42:26.199
And the barium ion is like interacting with the uterbium ion.

1887
01:42:26.219 --> 01:42:27.539
They're all in the same trap.

1888
01:42:28.199 --> 01:42:31.800
The barium ion is also going to get cooled, but it's not going to lose its quantum information.

1889
01:42:31.820 --> 01:42:33.000
I thought that was kind of cool.

1890
01:42:33.020 --> 01:42:34.421
And that's why you see the circle.

1891
01:42:34.441 --> 01:42:36.181
There's like a small circle and a bigger circle.

1892
01:42:36.201 --> 01:42:41.062
The bigger circle is the uterbium ion that we're using to cool down the barium.

1893
01:42:41.342 --> 01:42:42.643
I thought that was a cool trick.

1894
01:42:42.703 --> 01:42:44.123
It's like a conduit.

1895
01:42:44.223 --> 01:42:52.705
It's basically it becomes this companion that offloads the cooling function that gets passed on to the barium,

1896
01:42:54.045 --> 01:42:57.426
in such a way that allows the barium to retain its quantum information.

1897
01:42:57.526 --> 01:42:58.226
Yes.

1898
01:42:58.626 --> 01:43:00.627
But it's always paired.

1899
01:43:00.687 --> 01:43:08.189
The barium's always paired with the uterine in order to be able to, in the quantum logic part of the system, manage...

1900
01:43:08.309 --> 01:43:08.869
Everywhere.

1901
01:43:09.289 --> 01:43:09.829
Even in the memory.

1902
01:43:09.889 --> 01:43:11.150
Even in the memory part.

1903
01:43:11.170 --> 01:43:12.430
To basically manage its cooling...

1904
01:43:13.491 --> 01:43:17.476
aspect to it, which is quite cool.

1905
01:43:18.137 --> 01:43:20.760
As a small side note, this is maybe unrelated.

1906
01:43:21.200 --> 01:43:27.048
We've talked about the von Neumann bottleneck when you separate your memory from your processor.

1907
01:43:27.588 --> 01:43:31.253
Is there a similar problem in this type of system because we're separating the two?

1908
01:43:31.677 --> 01:43:35.078
Where you get some inefficiency because you have to translate.

1909
01:43:35.438 --> 01:43:36.598
I mean, I think kind of, yes.

1910
01:43:36.718 --> 01:43:38.259
Like, you know what I'm trying to ask?

1911
01:43:38.319 --> 01:43:38.919
I think totally.

1912
01:43:38.979 --> 01:43:44.941
Because, I mean, you have to move stuff around in order to get into the processing part, right?

1913
01:43:45.001 --> 01:43:47.562
And so this is the whole all-to-all connectivity two at a time.

1914
01:43:47.582 --> 01:43:48.182
Two at a time.

1915
01:43:48.282 --> 01:43:48.502
Right?

1916
01:43:48.582 --> 01:43:51.883
Because in the processor part, you can only have these things two at a time.

1917
01:43:52.303 --> 01:43:54.885
And then you're applying these logic gates using your lasers, right?

1918
01:43:55.005 --> 01:43:55.666
Yeah, yeah.

1919
01:43:55.886 --> 01:43:57.107
And so in part, the architect...

1920
01:43:57.127 --> 01:44:04.393
But you can do this with trapped ions because the coherence time is long enough that you can move this stuff around and kind of retain that information.

1921
01:44:04.413 --> 01:44:04.913
That makes sense.

1922
01:44:04.953 --> 01:44:05.473
No, that makes sense.

1923
01:44:05.493 --> 01:44:05.714
Okay.

1924
01:44:05.834 --> 01:44:06.034
Okay.

1925
01:44:06.114 --> 01:44:06.294
Yes.

1926
01:44:06.634 --> 01:44:06.774
Yes.

1927
01:44:06.814 --> 01:44:06.995
Yeah.

1928
01:44:07.395 --> 01:44:07.575
Okay.

1929
01:44:07.595 --> 01:44:08.676
So I thought that was kind of cool.

1930
01:44:08.696 --> 01:44:09.777
We've talked about quality.

1931
01:44:10.477 --> 01:44:30.297
uh very high yeah the quality is very high the gate times might be a little too long um control is pretty cool but again you have the slowness associated with moving stuff around but some cleverness in implementation scalability and economics scalability and economics is next this is where i think the architecture kind of hits the wall okay um

1932
01:44:31.337 --> 01:44:36.941
What they did with Helios, continuum, what they did with Helios, I think they know that they can't do this for larger systems.

1933
01:44:37.521 --> 01:44:37.802
Okay.

1934
01:44:37.882 --> 01:44:41.564
Because you can only really fit like 30 to 50 ions in that linear chain.

1935
01:44:41.604 --> 01:44:42.745
I don't know how many they fit actually.

1936
01:44:43.085 --> 01:44:44.807
No, with Helios, obviously, it was like 98.

1937
01:44:45.167 --> 01:44:45.327
Right?

1938
01:44:45.347 --> 01:44:47.769
So they had much more than, let's say like 200-ish.

1939
01:44:48.049 --> 01:44:52.552
But if you want to get to many, many more, that thing is not going to work.

1940
01:44:52.692 --> 01:44:54.533
That sort of architecture is not going to work.

1941
01:44:54.834 --> 01:45:00.438
To scale up, you need this atomic highway to do all sorts of

1942
01:45:01.178 --> 01:45:23.394
weird things um and it might be a real nightmare when it comes to optical engineering lasers are not great to work laser beam laser beams are not great to work with i'm gonna be honest okay um if you want to do arbitrary greats arbitrary gates on millions of ions you're gonna need like

1943
01:45:24.560 --> 01:45:27.623
a bunch of really perfectly aligned laser beams.

1944
01:45:28.183 --> 01:45:29.204
Okay.

1945
01:45:29.364 --> 01:45:31.966
There's going to be these like spatial light modulators.

1946
01:45:32.867 --> 01:45:37.871
There's going to be massive lenses that are all going to be pointing inside this vacuum chamber.

1947
01:45:38.852 --> 01:45:41.094
Now that's going to heat stuff up first.

1948
01:45:41.394 --> 01:45:45.058
You're pumping in lasers into a thing that's supposed to be cold.

1949
01:45:45.678 --> 01:45:46.518
You're heating stuff up.

1950
01:45:46.538 --> 01:45:50.639
And it's like the more lasers you add, it changes the economics of the equation.

1951
01:45:50.999 --> 01:45:51.399
Right.

1952
01:45:51.479 --> 01:45:55.080
It's not like a linear where it's like, oh, one additional laser means just like one additional.

1953
01:45:55.120 --> 01:45:55.400
Yeah.

1954
01:45:56.100 --> 01:45:57.700
It becomes more complex.

1955
01:45:57.820 --> 01:45:58.060
Anyway.

1956
01:45:58.280 --> 01:45:58.800
Exactly.

1957
01:45:59.360 --> 01:45:59.640
Okay.

1958
01:45:59.820 --> 01:46:05.561
And, you know, if let's say like some random thermal expansion changes the lens shape.

1959
01:46:07.042 --> 01:46:07.242
Right.

1960
01:46:07.622 --> 01:46:07.822
Right.

1961
01:46:08.562 --> 01:46:08.702
Right.

1962
01:46:08.722 --> 01:46:09.302
Then everything else.

1963
01:46:09.322 --> 01:46:11.323
Then like the laser is not pointing somewhere.

1964
01:46:11.603 --> 01:46:11.743
Right.

1965
01:46:11.783 --> 01:46:12.703
Now you got to deal with that.

1966
01:46:13.003 --> 01:46:13.903
Lasers are just tough.

1967
01:46:14.283 --> 01:46:14.443
Yeah.

1968
01:46:14.563 --> 01:46:14.824
Okay?

1969
01:46:14.964 --> 01:46:17.206
Lasers are tough.

1970
01:46:17.306 --> 01:46:19.768
The other thing about the economics part of things, right?

1971
01:46:20.628 --> 01:46:23.471
With superconducting circuits, I told you that, you know, it's going to be big.

1972
01:46:23.791 --> 01:46:24.992
These things are going to be massive.

1973
01:46:25.052 --> 01:46:25.172
Yeah.

1974
01:46:25.853 --> 01:46:29.816
Well, with this, the algorithms are going to take a really, really long time.

1975
01:46:30.797 --> 01:46:32.258
Because the gate times are so long.

1976
01:46:32.318 --> 01:46:32.678
Yeah.

1977
01:46:32.799 --> 01:46:32.999
Right?

1978
01:46:33.039 --> 01:46:35.881
They're like a thousand times longer than the superconducting circuits.

1979
01:46:36.201 --> 01:46:37.703
There have been estimates that show...

1980
01:46:38.655 --> 01:46:45.259
And obviously these are biased estimates, but this is a biased show, so we're going to talk about the biased estimates.

1981
01:46:45.959 --> 01:46:57.425
It shows that superconducting arrays, if they want to crack 2048-bit RSA encryption, it's going to take them about eight hours with a scalable, fault-tolerant quantum computer.

1982
01:46:57.686 --> 01:47:03.669
Here, even if we achieve scale, because the gate times are so slow, it might take on the order of a year.

1983
01:47:05.146 --> 01:47:09.028
to decrypt 2048 RSA.

1984
01:47:09.068 --> 01:47:11.089
Which defeats the purpose of why we want these systems.

1985
01:47:11.129 --> 01:47:11.710
Yeah, yeah, yeah.

1986
01:47:11.870 --> 01:47:14.531
I mean, you could say that... Yeah, yeah, it's one of the reasons, right?

1987
01:47:14.551 --> 01:47:20.974
You could say there are other uses for quantum computing, but as I talked about last episode...

1988
01:47:23.312 --> 01:47:25.433
The one that's clear to me is Shor's algorithm.

1989
01:47:25.493 --> 01:47:25.693
Yeah.

1990
01:47:26.034 --> 01:47:26.254
Right?

1991
01:47:26.434 --> 01:47:29.175
It's like everyone wants to decrypt stuff.

1992
01:47:29.956 --> 01:47:35.039
And that's also the geopolitical incentive.

1993
01:47:35.179 --> 01:47:35.639
Exactly.

1994
01:47:35.859 --> 01:47:39.381
Which is a driver of the investment into the space.

1995
01:47:39.421 --> 01:47:39.621
Yeah.

1996
01:47:39.681 --> 01:47:42.703
I mean, so Continuum, they have a lot of private funding.

1997
01:47:43.243 --> 01:47:50.828
I think Honeywell is one of the big computer chip technology firms, is I think one of the big sponsors.

1998
01:47:50.968 --> 01:47:51.348
Also...

1999
01:47:52.049 --> 01:47:58.474
JP Morgan, I think they want to do financial algorithms and portfolio management with quantum computers.

2000
01:47:58.514 --> 01:47:59.315
More power to them.

2001
01:47:59.975 --> 01:48:02.457
I'm not convinced.

2002
01:48:03.118 --> 01:48:06.141
So there are use cases for it.

2003
01:48:06.561 --> 01:48:12.766
And they obviously have the backing, private backing, and now public backing with the IPO.

2004
01:48:13.267 --> 01:48:18.011
And I'm actually excited to see what they're going to come up with for their next iteration after Helios.

2005
01:48:18.031 --> 01:48:18.271
Because

2006
01:48:20.151 --> 01:48:26.721
One of the things that we're going to get into later is the fact that algorithms are getting more and more efficient.

2007
01:48:27.422 --> 01:48:30.667
So maybe you don't need that many qubits and that many gates to do stuff.

2008
01:48:30.767 --> 01:48:31.788
And it could be irrelevant.

2009
01:48:32.269 --> 01:48:33.591
So it's an open problem, right?

2010
01:48:33.972 --> 01:48:36.015
But in any case, as of now...

2011
01:48:37.196 --> 01:48:44.847
With all of the optical engineering, like if it takes a year for you to do RSA, like in that year, your lasers have to be perfect, right?

2012
01:48:44.887 --> 01:48:45.448
For a whole year.

2013
01:48:45.528 --> 01:48:47.111
Like it's tough, right?

2014
01:48:47.531 --> 01:48:50.435
So again, opinions are all my own.

2015
01:48:50.836 --> 01:48:51.517
Final verdict.

2016
01:48:52.659 --> 01:48:54.421
The same as superconducting.

2017
01:48:54.581 --> 01:49:00.069
If you say that I copied the slide and just replaced it, that is actually exactly what I did.

2018
01:49:01.170 --> 01:49:02.272
But again, proprietary.

2019
01:49:02.833 --> 01:49:06.898
The standards by which we judge things is proprietary.

2020
01:49:06.999 --> 01:49:08.220
Cupid quality, 5 out of 10.

2021
01:49:08.300 --> 01:49:09.362
Cupid control, 5 out of 10.

2022
01:49:09.822 --> 01:49:35.956
scalability and economics 1 out of 10 to get 11 out of 30 what i would say just as a brief side note is that being said with the same score the lever in which superconducting qubits versus trapped ions could change uh the levers they would pull are different um yeah right like with with trapped ions if the algorithm problem goes away the scalability in economics very quickly um

2023
01:49:36.676 --> 01:49:59.951
is a solved problem as an example yeah and so while they're they're similarly scored the levers of changing are fundamentally different yes yeah and as as time goes on there's a there's an interesting plot oh i wish i'd had this overlay you know but maybe i'll put it up uh in the clips later go on go on instagram um there's a plot that shows um on the on the x-axis time and on the y-axis like

2024
01:50:00.551 --> 01:50:02.492
the efficiency of the algorithm effectively.

2025
01:50:02.512 --> 01:50:08.614
Like how many qubits do you need or how many gate, how many Clifford gates do you need to, or whatever gates that you need to implement.

2026
01:50:08.895 --> 01:50:10.975
And like, it's steadily decreasing as time goes on.

2027
01:50:11.015 --> 01:50:14.577
People are finding more and more efficient ways to, to implement this kind of stuff.

2028
01:50:14.895 --> 01:50:18.618
It's like the, not quite, but it's like the inverse of Moore's Law.

2029
01:50:19.039 --> 01:50:19.419
Yeah.

2030
01:50:20.160 --> 01:50:22.422
Not quite, because Moore's Law is a little bit, the numbers are a little different.

2031
01:50:22.442 --> 01:50:23.142
Yeah, well, it depends.

2032
01:50:23.182 --> 01:50:27.006
I mean, if you do Moore's Law size of transistor, that's going down, right?

2033
01:50:27.026 --> 01:50:27.986
Oh, that's going down, yeah, okay.

2034
01:50:28.026 --> 01:50:31.189
Moore's Law is traditionally number of transistors in a chip, and that goes up.

2035
01:50:31.209 --> 01:50:33.591
But you could do it one way or the other.

2036
01:50:33.611 --> 01:50:34.692
So that's trapped ions.

2037
01:50:34.772 --> 01:50:36.834
So we've covered superconducting qubits.

2038
01:50:37.395 --> 01:50:38.716
We've covered trapped ions.

2039
01:50:39.276 --> 01:50:42.179
And then the next thing we're going to look at.

2040
01:50:43.444 --> 01:50:44.164
Neutral atoms.

2041
01:50:44.225 --> 01:50:44.825
Neutral atoms.

2042
01:50:44.865 --> 01:50:46.026
I didn't even want to do this.

2043
01:50:46.506 --> 01:50:47.927
But we got it.

2044
01:50:48.027 --> 01:50:53.310
For our audience, we're always going to give you the best you can get anywhere.

2045
01:50:53.510 --> 01:50:54.051
This is the best.

2046
01:50:54.211 --> 01:50:54.771
This is the best.

2047
01:50:55.371 --> 01:50:57.173
So we're finally going to do neutral atoms.

2048
01:50:58.553 --> 01:51:00.875
There's a bunch of companies that are actually trying to do neutral atoms.

2049
01:51:00.915 --> 01:51:03.036
Qera, Pascal, Atom Computing.

2050
01:51:03.156 --> 01:51:06.799
Or Atomic is a new one that came out of Caltech, actually.

2051
01:51:06.859 --> 01:51:07.799
And it raised like $300 million.

2052
01:51:07.819 --> 01:51:07.919
Yeah.

2053
01:51:09.400 --> 01:51:11.461
on low qubit quantum computing.

2054
01:51:11.842 --> 01:51:15.564
Their idea is that they actually don't need that many qubits.

2055
01:51:15.744 --> 01:51:21.868
Their physical to logical qubit ratio is very low.

2056
01:51:21.928 --> 01:51:24.409
That's the claim they're making.

2057
01:51:25.029 --> 01:51:28.091
But let's try to get behind the PR hype here.

2058
01:51:28.191 --> 01:51:28.972
So what is the qubit?

2059
01:51:29.652 --> 01:51:35.556
So like trapped ions, the qubit is a real pristine atom, but it's not ionized.

2060
01:51:35.596 --> 01:51:37.237
Most of the time it's like a rubidium atom,

2061
01:51:38.240 --> 01:51:45.992
or a cesium atom, these are coincidentally the same atoms that are used in atomic clocks, and for a very good reason, because they're highly tunable,

2062
01:51:46.737 --> 01:51:47.597
highly precise.

2063
01:51:47.657 --> 01:51:52.439
The transitions are like highly precise and you can manage them very well with like lasers.

2064
01:51:52.459 --> 01:51:57.681
There's no electric charge and because they're neutral, we can't confine them using that pall trap.

2065
01:51:58.101 --> 01:52:00.962
Right, with the electrostatic fields.

2066
01:52:01.542 --> 01:52:05.483
So instead you trap it in midair using optical tweezers.

2067
01:52:05.583 --> 01:52:09.384
I shouldn't say midair, really it's mid-vacuum, right?

2068
01:52:09.804 --> 01:52:11.805
But you trap it with an optical tweezer.

2069
01:52:11.845 --> 01:52:14.686
It's a highly focused laser beam where...

2070
01:52:15.542 --> 01:52:22.450
Because of the physics of the laser beam being focused, the neutral atom wants to live at the focus of that laser beam.

2071
01:52:22.730 --> 01:52:25.393
There's like a dipole force that happens that restores.

2072
01:52:25.413 --> 01:52:29.678
Like every time the atom moves away, there's a dipole force that restores it back.

2073
01:52:30.158 --> 01:52:31.900
The qubit states are 0 and 1.

2074
01:52:32.040 --> 01:52:33.843
And again, it's the hyperfine clock states.

2075
01:52:34.723 --> 01:52:37.725
So we basically can point at it and be like, stay right here.

2076
01:52:38.385 --> 01:52:39.465
Yeah, there's like a laser.

2077
01:52:39.485 --> 01:52:40.246
You concentrate it.

2078
01:52:40.526 --> 01:52:41.687
You make it stay right there.

2079
01:52:42.187 --> 01:52:46.329
And it's the same super stable spin transitions that are used in atomic clocks.

2080
01:52:46.809 --> 01:52:48.030
It's like a tractor beam.

2081
01:52:48.550 --> 01:52:49.190
It is kind of.

2082
01:52:49.630 --> 01:52:50.871
Actually, exactly.

2083
01:52:50.891 --> 01:52:54.413
A tractor beam is like, yeah, that's exactly right.

2084
01:52:54.513 --> 01:52:57.014
It's a tractor beam.

2085
01:52:58.014 --> 01:52:58.935
Now, the problem is...

2086
01:53:00.378 --> 01:53:02.801
Actually, before we get into the problem, how do we talk to it?

2087
01:53:03.201 --> 01:53:05.063
Well, we use lasers, just like trapped ions.

2088
01:53:05.083 --> 01:53:05.823
We use lasers.

2089
01:53:06.164 --> 01:53:10.768
Single-cubit gates are driven by two-photon Raman laser pulses.

2090
01:53:10.788 --> 01:53:11.709
We don't have to get into it.

2091
01:53:12.109 --> 01:53:14.412
Two-cubit gates are a bit different.

2092
01:53:14.432 --> 01:53:23.060
Now, instead of using sound waves like we did with trapped ions, we are going to use something called a Rydeberg state and the Rydeberg blockade.

2093
01:53:23.100 --> 01:53:23.680
Here's the idea.

2094
01:53:24.181 --> 01:53:25.322
You pump a laser into it.

2095
01:53:26.524 --> 01:53:31.390
So that the electron that's on the outside gets knocked to a really high energy level.

2096
01:53:31.410 --> 01:53:31.871
Okay.

2097
01:53:32.051 --> 01:53:32.311
Okay?

2098
01:53:32.571 --> 01:53:41.062
Like, imagine you're taking an electron that's in the orbit of, like, Earth near the nucleus, and you're knocking it all the way out to Pluto.

2099
01:53:41.542 --> 01:53:42.023
Oh, yes.

2100
01:53:42.043 --> 01:53:43.565
That's quite some distance.

2101
01:53:43.745 --> 01:53:45.988
You've increased the size of the atom.

2102
01:53:46.008 --> 01:53:46.148
Okay.

2103
01:53:47.243 --> 01:53:50.004
By a massive amount, like almost by a factor of a million.

2104
01:53:50.404 --> 01:53:55.325
Because now the orbit of the electron... Is like out where Pluto is, kind of, right?

2105
01:53:55.665 --> 01:54:05.148
Now, because this atom is now very big, and its neighboring atoms are still the same size, let's say, it's going to start having effects on the neighboring atom.

2106
01:54:05.208 --> 01:54:07.208
The neighboring atom is going to start getting nudged.

2107
01:54:07.568 --> 01:54:11.709
That physical volume is going to start nudging this atom.

2108
01:54:12.409 --> 01:54:14.830
And that massive shift...

2109
01:54:16.390 --> 01:54:19.173
is going to make the other atom shift its energy levels.

2110
01:54:19.213 --> 01:54:19.453
Yeah.

2111
01:54:19.794 --> 01:54:20.034
Okay?

2112
01:54:20.615 --> 01:54:25.340
And then whatever laser can no longer excite the other atom.

2113
01:54:26.080 --> 01:54:27.802
This is how you do entangling, effectively.

2114
01:54:28.043 --> 01:54:37.733
You're making them talk based on something called a Vanderwaal's force, which is like volume becoming fat and making the volume do the talking.

2115
01:54:38.311 --> 01:54:46.323
So, again, so previously we used sound as the basically the vector by which we, you know, had the communication between the qubits.

2116
01:54:46.943 --> 01:54:53.192
Now we're seeing this like very like fast, almost instantaneous, massive change in volume.

2117
01:54:54.073 --> 01:54:58.397
has these derivative impacts on the other qubits in the system.

2118
01:54:58.777 --> 01:55:00.018
And that's what's communicating.

2119
01:55:00.038 --> 01:55:08.705
So we're going to make it go from a current size to very, very big in a very particular way because we then know how that volume change is going to impact the other qubits.

2120
01:55:08.725 --> 01:55:17.332
And then we read – that's the way to communicate the zero-one – to communicate in this two qubit plus states.

2121
01:55:17.412 --> 01:55:18.313
Plus states, yeah.

2122
01:55:18.413 --> 01:55:20.515
It's how you make the qubits talk to one another is –

2123
01:55:21.075 --> 01:55:28.337
blow it up, and then because this thing is blowed up, the other stuff is going to be like, whoa, and that's your entangling, and that's your two-qubit gates.

2124
01:55:28.817 --> 01:55:29.317
Interesting.

2125
01:55:29.437 --> 01:55:29.917
Interesting.

2126
01:55:29.977 --> 01:55:31.978
I mean, I wouldn't do it that way, but whatever.

2127
01:55:32.258 --> 01:55:33.798
Look, interesting.

2128
01:55:34.519 --> 01:55:46.962
So one of the problems here, though, is that with the trapped ions, because it was an ion hyperfine frequency, and the difference between the zero and the one

2129
01:55:47.918 --> 01:55:51.744
is very far away from the infrared stuff that we see at room temperature.

2130
01:55:52.425 --> 01:55:54.487
Here, though, the thing is not ionized.

2131
01:55:54.608 --> 01:55:56.490
It's just at a really high Pluto orbit.

2132
01:55:56.610 --> 01:55:58.773
And this goes back to the rungs of the ladder.

2133
01:55:58.794 --> 01:55:59.795
Yeah, the rungs of the ladder.

2134
01:55:59.835 --> 01:56:01.898
Before the rungs of the ladder were very big, so then

2135
01:56:02.348 --> 01:56:04.430
If infrared came in, eh, it doesn't matter.

2136
01:56:04.730 --> 01:56:12.297
Here, though, because you're now at Pluto's orbit, Pluto plus one is actually kind of nearby.

2137
01:56:12.317 --> 01:56:13.097
Yeah.

2138
01:56:13.357 --> 01:56:18.322
So the infrared bath that I'm in might actually start knocking you into these other registers.

2139
01:56:18.582 --> 01:56:20.263
In a way that entrapped ions, it did not.

2140
01:56:20.323 --> 01:56:21.484
It did not, right?

2141
01:56:21.745 --> 01:56:24.107
So that's a problem that they need to deal with.

2142
01:56:24.747 --> 01:56:24.947
Okay.

2143
01:56:25.308 --> 01:56:26.709
Oh, let's go into cubic quality now.

2144
01:56:26.749 --> 01:56:28.290
Let's go into the FFP audit.

2145
01:56:28.330 --> 01:56:29.091
The strength here...

2146
01:56:30.871 --> 01:56:36.115
You can pack thousands of them into a tiny 2D or 3D array.

2147
01:56:36.536 --> 01:56:36.816
Okay.

2148
01:56:37.016 --> 01:56:37.276
Okay?

2149
01:56:37.537 --> 01:56:40.479
You can have a bunch of these optical tweezers, and you can make a grid.

2150
01:56:40.499 --> 01:56:41.440
Like, this is kind of cool.

2151
01:56:41.760 --> 01:56:45.003
You've got a grid of neutral atoms that are all together.

2152
01:56:45.023 --> 01:56:45.343
Mm-hmm.

2153
01:56:46.058 --> 01:56:47.299
that are packed in.

2154
01:56:47.799 --> 01:56:50.500
And each of those is a single atom that you're looking at.

2155
01:56:50.900 --> 01:56:53.721
That's suspended in a checkerboard pattern.

2156
01:56:53.741 --> 01:56:54.581
In a sunbeam.

2157
01:56:54.921 --> 01:56:56.842
It's kind of cool.

2158
01:56:56.942 --> 01:57:00.423
And each of these is spaced just like four or five microns apart.

2159
01:57:00.663 --> 01:57:00.983
Okay.

2160
01:57:01.103 --> 01:57:01.743
So it's quite small.

2161
01:57:01.843 --> 01:57:03.203
So it's quite small, right, yeah.

2162
01:57:03.323 --> 01:57:05.404
And the physical density is quite large, right?

2163
01:57:05.584 --> 01:57:07.284
That's actually pretty cool architecturally.

2164
01:57:07.384 --> 01:57:08.244
Architecturally, right.

2165
01:57:08.564 --> 01:57:14.526
And now a lot of these groups, they report fidelities that are really high, 99.5% gate fidelity.

2166
01:57:14.826 --> 01:57:19.166
Like the way that they're moving these things around, it's like very, very accurate.

2167
01:57:19.226 --> 01:57:20.727
But you read the fine print.

2168
01:57:22.587 --> 01:57:23.587
You read the fine print.

2169
01:57:25.368 --> 01:57:26.868
What's actually happening is the following.

2170
01:57:29.034 --> 01:57:31.618
during their experiment, they will lose atoms.

2171
01:57:32.859 --> 01:57:36.424
Because the atoms are in this tractor beam.

2172
01:57:36.945 --> 01:57:37.946
Sometimes they'll leave.

2173
01:57:38.006 --> 01:57:39.948
Sometimes the photon will come in, they'll leave.

2174
01:57:40.369 --> 01:57:42.432
Another atom from the vacuum will come in, they'll leave.

2175
01:57:42.452 --> 01:57:43.453
They're going to lose atoms.

2176
01:57:43.813 --> 01:57:46.577
Every time they lose atoms, they just throw away that experiment.

2177
01:57:50.088 --> 01:57:50.969
That doesn't count.

2178
01:57:51.309 --> 01:57:53.010
Yeah, they're just like, ah.

2179
01:57:53.030 --> 01:57:53.891
We have so many of them.

2180
01:57:54.031 --> 01:57:55.873
Yeah, yeah, let's just do it again.

2181
01:57:56.173 --> 01:58:06.161
And then so there's this post-selection, and many of the published fidelity figures calculate conditioned on Adam's survival.

2182
01:58:06.181 --> 01:58:08.102
They throw away the trials where the Adams died.

2183
01:58:08.903 --> 01:58:09.744
Which doesn't count.

2184
01:58:09.764 --> 01:58:11.606
Which is like, I mean, there's a reason.

2185
01:58:11.887 --> 01:58:14.670
Okay, there might be a good reason for you to do that.

2186
01:58:15.130 --> 01:58:20.236
But then at the same time, I should be able to say, is that the same as the numbers that other people are reporting?

2187
01:58:20.577 --> 01:58:26.524
If I'm running a hundred meter dash and I can run it a hundred times and just throw out the ones I don't like...

2188
01:58:27.645 --> 01:58:28.425
Does it still count?

2189
01:58:28.625 --> 01:58:30.586
Yeah.

2190
01:58:31.126 --> 01:58:31.546
I don't know.

2191
01:58:31.746 --> 01:58:32.267
I don't know.

2192
01:58:32.427 --> 01:58:33.047
I'm a layman.

2193
01:58:33.127 --> 01:58:37.308
I'm just asking the question because that's what it sounds like to me.

2194
01:58:37.689 --> 01:58:41.510
But please convince – I can be dissuaded from this perspective.

2195
01:58:41.570 --> 01:58:41.770
Yeah.

2196
01:58:41.950 --> 01:58:43.531
Anyway, so that's cubit quality, right?

2197
01:58:44.051 --> 01:58:45.031
The quality of the cubit.

2198
01:58:45.551 --> 01:58:45.751
All right.

2199
01:58:45.831 --> 01:58:46.632
What about control?

2200
01:58:47.592 --> 01:58:52.934
Control – like the fact that you can use these laser beams, you can bring any two atoms together.

2201
01:58:52.954 --> 01:58:53.294
Mm-hmm.

2202
01:58:54.094 --> 01:59:00.479
And you can make the tweezers sort of grab this atom and this atom and bring them together, grab this atom and this atom.

2203
01:59:00.779 --> 01:59:03.921
This is an experiment where they showed, like, using these tractor beams,

2204
01:59:04.268 --> 01:59:08.209
They can create like a 3D sculpture of stuff, which is kind of cool.

2205
01:59:08.229 --> 01:59:08.769
That's very cool.

2206
01:59:08.989 --> 01:59:09.529
Right?

2207
01:59:09.669 --> 01:59:13.210
And so this is to show you that you can physically move them across the array.

2208
01:59:13.230 --> 01:59:15.831
You can park them right next to new orbits, mid-circuit.

2209
01:59:16.131 --> 01:59:19.012
So you can have like this all-to-all connectivity type of thing.

2210
01:59:19.252 --> 01:59:23.593
And because you have all-to-all connectivity, you can now... Not limited by two.

2211
01:59:23.853 --> 01:59:24.813
Not limited by two, right?

2212
01:59:24.833 --> 01:59:25.293
By trapped ion.

2213
01:59:25.393 --> 01:59:26.374
Exactly, yeah.

2214
01:59:26.414 --> 01:59:27.134
So now you can...

2215
01:59:27.634 --> 01:59:32.756
you can do error codes that are like way more efficient, right?

2216
01:59:32.936 --> 01:59:36.957
Because you can harness this all-to-all connectivity.

2217
01:59:37.478 --> 01:59:47.721
The readout, however, is kind of destructive because you do it by shining a laser and capturing the fluorescent photons, but the light pressure from this readout can heat up the atoms and then, again, they'll like leave.

2218
01:59:48.101 --> 01:59:49.442
But then I guess you can just throw it out.

2219
01:59:49.602 --> 01:59:50.842
Yeah.

2220
01:59:50.942 --> 01:59:52.343
Would this then sort of mean like,

2221
01:59:52.883 --> 02:00:07.493
the idea is that we're solving for lack of coherence time in this kind of system which was great in trapped ions but is not necessarily as great here by just saying we can scale this so much we can just have so many that coherence time is not no longer as important of a variable

2222
02:00:07.633 --> 02:00:12.535
Yeah, it's like, I mean, coherence time might not be the correct idea, but I think like survival.

2223
02:00:12.575 --> 02:00:12.955
Survival.

2224
02:00:12.975 --> 02:00:13.895
It's like cubit survival.

2225
02:00:13.935 --> 02:00:14.395
Yeah, right.

2226
02:00:14.475 --> 02:00:18.737
It's like, yeah, it might not be because maybe the gates are a little bit more faster.

2227
02:00:19.097 --> 02:00:22.038
And I mean, the community is saying that they are working on it.

2228
02:00:22.418 --> 02:00:22.678
Okay.

2229
02:00:22.878 --> 02:00:23.139
Okay?

2230
02:00:23.339 --> 02:00:24.439
They're working on this problem.

2231
02:00:24.459 --> 02:00:27.160
And they've got these ideas where they've got a reservoir.

2232
02:00:27.700 --> 02:00:31.842
where they can take the atom from the reservoir and put it in where the, where it was missing.

2233
02:00:32.022 --> 02:00:35.663
The key thing is it's, it gets pretty obvious to know where the atom left.

2234
02:00:35.743 --> 02:00:35.983
Right.

2235
02:00:36.043 --> 02:00:36.263
Yeah.

2236
02:00:36.383 --> 02:00:36.543
Yeah.

2237
02:00:36.583 --> 02:00:36.763
Right.

2238
02:00:36.783 --> 02:00:38.104
Because you've got a grid or whatever.

2239
02:00:38.344 --> 02:00:38.824
Right.

2240
02:00:38.844 --> 02:00:46.106
And because you know exactly where the atom left, the error codes where, you know, where the error happened are really efficient.

2241
02:00:46.146 --> 02:00:46.306
Yeah.

2242
02:00:46.386 --> 02:00:47.007
And that makes sense.

2243
02:00:47.307 --> 02:00:56.990
And again, these systems sort of have optimizations for different things or are successful in different arenas that, uh,

2244
02:00:57.670 --> 02:01:00.031
Maybe other methodologies don't do as well.

2245
02:01:00.451 --> 02:01:14.657
But the idea, again, going back to our original analogy of the transistor versus vacuum tube versus electric relays, it's still unclear right now, you'll make the argument otherwise, right now, which path is going to be.

2246
02:01:14.877 --> 02:01:24.080
Because there's going to be, maybe there are use cases for some niche areas for some of these, if there's not an outright winner, that's just good for everything.

2247
02:01:24.100 --> 02:01:24.801
Maybe that's true.

2248
02:01:25.521 --> 02:01:34.607
But it's also very possible that one of these is just going to solve each of these layers and just be the best for everything.

2249
02:01:35.267 --> 02:01:42.391
And in this case, the architecture for these neutral atoms is really nice because you have a lot of fine grain control.

2250
02:01:42.491 --> 02:01:42.692
Yeah.

2251
02:01:42.772 --> 02:01:46.574
And that's why I think a lot of people think that this is the current sort of frontrunner.

2252
02:01:46.854 --> 02:01:47.134
Okay.

2253
02:01:47.274 --> 02:01:47.514
Okay.

2254
02:01:47.634 --> 02:01:49.015
Because it's out there, yeah.

2255
02:01:49.055 --> 02:01:51.797
You've got all these nice little knobs that you can tune, right?

2256
02:01:52.037 --> 02:01:52.537
Okay.

2257
02:01:52.957 --> 02:01:56.619
And then to scale them, like how scalability?

2258
02:01:56.659 --> 02:02:02.022
Well, to scale them, you've got, you know, how many atoms can I put in my array?

2259
02:02:02.382 --> 02:02:02.562
Yeah.

2260
02:02:02.702 --> 02:02:03.522
That's the idea, right?

2261
02:02:03.542 --> 02:02:04.243
Yeah.

2262
02:02:04.423 --> 02:02:08.445
You can take a singular electron beam and split it up into a bunch of optical tweezers.

2263
02:02:09.558 --> 02:02:13.480
And then that's normally what we see when we saw that grid of atoms.

2264
02:02:13.800 --> 02:02:22.984
That's really a single laser beam that you're splitting into a bunch of optical tweezers, a bunch of tractor beams, and then each of the atoms are in that.

2265
02:02:23.444 --> 02:02:26.066
One of the problems, though, there's two problems really with this.

2266
02:02:26.226 --> 02:02:27.726
One is there's a laser power wall.

2267
02:02:28.187 --> 02:02:29.727
Like how powerful can you make your laser?

2268
02:02:29.927 --> 02:02:31.008
All right, you've got a thousand.

2269
02:02:31.028 --> 02:02:31.248
Yeah.

2270
02:02:31.995 --> 02:02:32.235
Right.

2271
02:02:32.315 --> 02:02:33.776
Can you like 10x your laser power?

2272
02:02:34.497 --> 02:02:40.761
If you 10x your laser power, can you not impart heat into the system?

2273
02:02:41.181 --> 02:02:48.526
And two, if you 10x your laser power, but the laser has some noise because the laser is not magically tuned to some frequency.

2274
02:02:48.546 --> 02:02:48.726
Right.

2275
02:02:48.946 --> 02:02:50.307
There's a jitter in the frequency.

2276
02:02:50.787 --> 02:02:55.010
And that frequency noise is going to be correlated across all of your beam splitters.

2277
02:02:55.950 --> 02:03:00.973
Each of the atoms is going to be receiving the same noise because it's coming from the same laser.

2278
02:03:01.654 --> 02:03:10.860
And crucially, for a lot of the error detection algorithms for the fault-tolerant computing, that relies on uncorrelated noise.

2279
02:03:10.920 --> 02:03:14.022
The assumption that the noise on all of these qubits is uncorrelated.

2280
02:03:14.062 --> 02:03:15.062
That's a good point.

2281
02:03:15.563 --> 02:03:17.804
So if it's all correlated because it's coming from the same source.

2282
02:03:17.864 --> 02:03:19.265
Same source, then like, you know...

2283
02:03:20.163 --> 02:03:20.583
That's good.

2284
02:03:20.924 --> 02:03:22.565
Might might be a problem.

2285
02:03:22.685 --> 02:03:22.985
Yeah.

2286
02:03:23.185 --> 02:03:23.405
Right.

2287
02:03:24.346 --> 02:03:35.054
There was also this really nice paper that came out in March 2026 that said that with just 10,000 quantum quantum bits, you might crack inherent encryption schemes.

2288
02:03:35.134 --> 02:03:38.276
This is out of Internet Internet encryption schemes.

2289
02:03:38.476 --> 02:03:41.778
Yeah, internet encryption schemes, but also Bitcoin is going to go to zero.

2290
02:03:41.798 --> 02:03:43.939
It's going to get your crypto wallets, everything.

2291
02:03:44.779 --> 02:03:46.120
As headlines tend to.

2292
02:03:46.140 --> 02:03:49.142
Yeah, this was out of Harvard, Caltech, and QARA.

2293
02:03:49.722 --> 02:03:53.284
Naturally, the press lost its mind.

2294
02:03:54.905 --> 02:03:57.486
But yet, mathematically, let's go into the paper.

2295
02:03:57.987 --> 02:04:00.528
They've got a little figure that shows you the space-time trade-off.

2296
02:04:01.957 --> 02:04:07.943
You're shuttling the atoms, and that's mechanically slow in order to do the error correction and things like that.

2297
02:04:08.884 --> 02:04:18.093
Even if you've got a 10,000 qubit array, it's going to take you a really, really long time.

2298
02:04:19.995 --> 02:04:23.519
If you've got 100,000 physical qubits, even then...

2299
02:04:24.882 --> 02:04:30.364
With mathematically optimal assumptions, it's going to take you about three months to crack RSA.

2300
02:04:30.504 --> 02:04:30.765
Okay?

2301
02:04:31.225 --> 02:04:31.465
Yeah.

2302
02:04:32.185 --> 02:04:34.346
With 10,000, it goes into, like, years.

2303
02:04:35.567 --> 02:04:37.728
Which is, again, not... Fine.

2304
02:04:37.928 --> 02:04:39.128
Your computer isn't that big.

2305
02:04:39.348 --> 02:04:39.528
Right.

2306
02:04:39.788 --> 02:04:39.989
Right?

2307
02:04:41.449 --> 02:04:42.830
But it's taking a year now.

2308
02:04:43.010 --> 02:04:43.190
Yeah.

2309
02:04:43.390 --> 02:04:43.590
Yeah.

2310
02:04:43.970 --> 02:04:45.971
And this goes back to the same issue we had with trapped ions.

2311
02:04:46.131 --> 02:04:46.371
Yeah.

2312
02:04:46.491 --> 02:04:52.454
Which is this cycle time is still... Yeah.

2313
02:04:54.439 --> 02:05:08.444
In my head, again, as someone who doesn't live in this space, all I keep hearing is like this will allow us to do what you couldn't do in the entirety of the existence of the universe in the snap of Thanos' finger.

2314
02:05:08.684 --> 02:05:11.065
So that's where my expectation level is.

2315
02:05:11.325 --> 02:05:15.767
Yeah, around time efficiency, specifically, independent of all the other details.

2316
02:05:16.147 --> 02:05:18.628
And so when I hear it, it's still going to take, I thought this was going to be instant.

2317
02:05:18.688 --> 02:05:18.928
No, no.

2318
02:05:18.969 --> 02:05:20.969
As soon as it's done, RSA will just be over.

2319
02:05:21.510 --> 02:05:22.730
Everyone can be hacked immediately.

2320
02:05:22.850 --> 02:05:26.552
No, I mean, those headlines would have made you think that.

2321
02:05:26.732 --> 02:05:26.912
Right.

2322
02:05:26.952 --> 02:05:29.596
But you go into the figures and it's like, no, it'll still take a year.

2323
02:05:29.656 --> 02:05:29.796
Yeah.

2324
02:05:29.956 --> 02:05:30.157
Yeah.

2325
02:05:30.297 --> 02:05:31.899
Which again, it's not a year.

2326
02:05:31.979 --> 02:05:34.342
It's not a year, but also that means no one's targeting me.

2327
02:05:35.344 --> 02:05:35.584
Right?

2328
02:05:35.644 --> 02:05:39.089
No one has like the one quantum computer and they're targeting my wallet.

2329
02:05:39.329 --> 02:05:41.632
It basically only gets critical infrastructure.

2330
02:05:41.652 --> 02:05:41.892
Yeah.

2331
02:05:42.653 --> 02:05:44.195
It becomes like a war thing.

2332
02:05:44.215 --> 02:05:44.536
Yeah.

2333
02:05:44.816 --> 02:05:44.977
Yeah.

2334
02:05:45.097 --> 02:05:45.317
Right.

2335
02:05:45.397 --> 02:05:45.718
Yeah.

2336
02:05:45.818 --> 02:05:50.264
And no one's going to use this to, to, to find the next room temperature superconductor.

2337
02:05:50.404 --> 02:05:50.584
Right.

2338
02:05:50.664 --> 02:05:52.367
Which is not, which is what we want to do.

2339
02:05:52.387 --> 02:05:53.007
That's the whole point.

2340
02:05:53.048 --> 02:05:53.188
Right.

2341
02:05:53.228 --> 02:05:53.508
Yeah.

2342
02:05:53.608 --> 02:05:55.371
And not just targeted for weapons systems.

2343
02:05:55.751 --> 02:05:56.112
Please.

2344
02:05:56.232 --> 02:05:58.054
So, so now we do the final verdict.

2345
02:05:58.967 --> 02:05:59.727
On neutral atoms.

2346
02:06:00.488 --> 02:06:03.869
Cubit quality, I give it a negative 1,000 out of 10.

2347
02:06:04.109 --> 02:06:05.310
Yes.

2348
02:06:05.390 --> 02:06:07.611
Cubit control, negative 1,000 out of 10.

2349
02:06:07.651 --> 02:06:08.171
Yes, yes.

2350
02:06:08.371 --> 02:06:14.934
And sustainability and economics, another negative 1,000 out of 10 for a total of negative 3,000 out of 30.

2351
02:06:14.954 --> 02:06:15.895
Yeah, yeah.

2352
02:06:16.155 --> 02:06:17.095
I think this is fair.

2353
02:06:17.575 --> 02:06:19.136
I think this is totally fair.

2354
02:06:20.137 --> 02:06:27.220
Again, the metrics are proprietary, FFP, proprietary, IP.

2355
02:06:27.260 --> 02:06:27.460
Yeah.

2356
02:06:29.045 --> 02:06:51.770
for all the neutral atoms community i could never have thought um you know since that night at alice and bob that neutral atoms would end up at negative 3 000 out of 30 but i that's how the cookie crumbles so what can you do this is where we started and and it's just not it's not good yeah it's just not good and you can complain about in the comments

2357
02:06:52.960 --> 02:06:54.623
But there's just nothing you can do about it.

2358
02:06:54.643 --> 02:07:01.753
And so we've now covered all of the top contenders but for the star of the show.

2359
02:07:01.813 --> 02:07:04.397
So we started at super – no, we didn't start.

2360
02:07:04.637 --> 02:07:07.261
We started, yeah, superconducting Qubits.

2361
02:07:08.482 --> 02:07:10.102
Then we went to trapped ions.

2362
02:07:11.063 --> 02:07:12.243
Then we went to neutral atoms.

2363
02:07:12.523 --> 02:07:12.963
The worst.

2364
02:07:13.183 --> 02:07:13.983
Yeah, the worst.

2365
02:07:14.263 --> 02:07:14.744
Negative 3,000.

2366
02:07:15.024 --> 02:07:15.964
Negative 3,000.

2367
02:07:16.284 --> 02:07:17.544
Right.

2368
02:07:17.564 --> 02:07:24.546
And all of them, we now have a very fundamental understanding of how they work across our three criteria.

2369
02:07:24.766 --> 02:07:24.966
Yeah.

2370
02:07:25.086 --> 02:07:29.267
Which is qubit quality, qubit control, and scalability and economics.

2371
02:07:29.647 --> 02:07:34.868
Which I think is a three-axis system that is really relevant to really try to understand what's going on.

2372
02:07:35.188 --> 02:07:37.889
When we're talking about building a quantum computer, what actually matters?

2373
02:07:38.269 --> 02:07:51.954
And from our part one, we have fundamentals of understanding all of the different weirdness that goes into the quantum mechanics and quantum algorithms and qubit state zero one, but with the phase and then the north south.

2374
02:08:05.495 --> 02:08:09.219
Something that people at the frontier didn't even know about.

2375
02:08:09.700 --> 02:08:10.140
That's right.

2376
02:08:10.581 --> 02:08:11.201
During your talk.

2377
02:08:11.301 --> 02:08:11.802
Yeah, yeah.

2378
02:08:11.982 --> 02:08:13.083
It's not made out of cheese.

2379
02:08:13.203 --> 02:08:14.084
It's not made out of cheese.

2380
02:08:14.104 --> 02:08:14.865
Made out of silicon.

2381
02:08:15.126 --> 02:08:17.828
And it's also on the front page of nature.

2382
02:08:18.009 --> 02:08:20.131
Unlike trapped ions.

2383
02:08:20.231 --> 02:08:20.391
Yeah.

2384
02:08:20.511 --> 02:08:20.932
Unlike...

2385
02:08:22.195 --> 02:08:22.955
Neutral atoms.

2386
02:08:22.975 --> 02:08:24.876
Trapped ions have been on the front.

2387
02:08:24.916 --> 02:08:27.057
We're talking about it in 2026.

2388
02:08:27.077 --> 02:08:27.337
2026.

2389
02:08:27.957 --> 02:08:28.357
Before.

2390
02:08:28.377 --> 02:08:29.317
The before times.

2391
02:08:29.737 --> 02:08:30.958
I don't know if neutral atoms have.

2392
02:08:31.358 --> 02:08:32.418
I know superconducting has.

2393
02:08:32.778 --> 02:08:32.998
Of course.

2394
02:08:33.098 --> 02:08:35.499
I didn't see in my research if neutral atoms have.

2395
02:08:35.659 --> 02:08:37.140
If they have, definitely put it in the comments.

2396
02:08:37.160 --> 02:08:38.600
Quantum supremacy, which is the superconducting.

2397
02:08:38.620 --> 02:08:39.701
That's the superconducting.

2398
02:08:39.721 --> 02:08:40.301
That's been on there.

2399
02:08:40.541 --> 02:08:43.782
So we've seen everybody make their claim on the cover.

2400
02:08:44.642 --> 02:08:50.124
Now it's time to see what the supreme qubit is.

2401
02:08:51.047 --> 02:08:55.690
is going to look like I'm giving a lot of setup here because this has been a whole Christian.

2402
02:08:55.710 --> 02:08:56.871
This has been a lot of hard work.

2403
02:08:56.951 --> 02:08:57.171
Yeah.

2404
02:08:57.351 --> 02:09:15.544
You've put a lot of blood, sweat and tears, not only into the work to be a part of this project, but to kind of put this series together to really give all of us as the audience, a real understanding of, of what it is this means and why in a biased way, you believe that this is the best option.

2405
02:09:15.584 --> 02:09:17.425
And so we are going to get now into this,

2406
02:09:19.107 --> 02:09:20.429
understanding spin qubits.

2407
02:09:20.670 --> 02:09:21.090
That's right.

2408
02:09:21.391 --> 02:09:22.192
We're finally here.

2409
02:09:22.512 --> 02:09:23.214
Spin qubits.

2410
02:09:23.514 --> 02:09:25.137
All right.

2411
02:09:25.357 --> 02:09:26.599
The nature cover...

2412
02:09:27.445 --> 02:09:28.445
Quantum silicon.

2413
02:09:28.645 --> 02:09:30.946
Which we will hang on the wall.

2414
02:09:31.006 --> 02:09:35.127
I think we're going to now replace our downtown LA with a gallery wall.

2415
02:09:35.207 --> 02:09:38.548
This will be our first addition to the gallery wall.

2416
02:09:38.588 --> 02:09:39.888
Something that is very important.

2417
02:09:40.108 --> 02:09:41.049
Yeah.

2418
02:09:41.189 --> 02:09:42.849
We've covered the three big technologies.

2419
02:09:43.609 --> 02:09:44.830
And now I want to get here.

2420
02:09:45.050 --> 02:09:47.711
The story actually starts in 1998.

2421
02:09:47.791 --> 02:09:48.931
We're going to do a little bit of history.

2422
02:09:48.951 --> 02:09:49.431
Okay.

2423
02:09:51.608 --> 02:10:01.717
The year 2020 marked the Physical Review A's 50th anniversary, and as part of the celebrations, the journal presented a collection of milestone papers, 50 milestone papers.

2424
02:10:02.098 --> 02:10:02.778
This was one of them.

2425
02:10:02.878 --> 02:10:04.360
It was listed as a milestone paper.

2426
02:10:04.680 --> 02:10:12.928
Quantum Computation with Quantum Dots by Daniel Loss, who was at UC Santa Barbara in Basel, and DiVincenzo.

2427
02:10:14.097 --> 02:10:16.600
who was at IBM and UC Santa Barbara.

2428
02:10:17.080 --> 02:10:23.588
So in this paper, Lawson DiVincenzo, they laid out a proposal for quantum computation based on quantum dots.

2429
02:10:24.008 --> 02:10:27.532
Quantum dots meaning little tiny localities of charge

2430
02:10:28.043 --> 02:10:29.984
that are in some kind of solid state device.

2431
02:10:30.764 --> 02:10:45.608
And it was a detailed investigation into how you can do one qubit gates, two qubit gates with these quantum dots, single electrons that are localized in some solid state device, in some like piece of metal.

2432
02:10:47.297 --> 02:10:54.420
Now, the idea is you're going to use some piece of metal to confine the electrons into a geographically isolated place.

2433
02:10:54.920 --> 02:11:05.945
This thing is going to have to be small, something like tens of nanometers for each electron's room, so to speak, because the electron's wave function is that big.

2434
02:11:05.965 --> 02:11:07.185
You don't want to fit too many.

2435
02:11:08.006 --> 02:11:09.906
So this thing has to be really small.

2436
02:11:10.927 --> 02:11:13.148
It's going to be confined in the z direction.

2437
02:11:13.928 --> 02:11:15.328
by the material itself.

2438
02:11:15.348 --> 02:11:18.189
And I think we've got a thing that shows that.

2439
02:11:18.209 --> 02:11:18.970
Yes.

2440
02:11:19.430 --> 02:11:30.473
So, you know, you can imagine you have a silicon substrate, like some kind of chip, and you do something to the silicon such that all of the electrons want to live in a plane.

2441
02:11:31.243 --> 02:11:36.749
So you get a two-dimensional electron gas, a 2-Deg is what they call it in the industry.

2442
02:11:37.811 --> 02:11:43.036
This can be either because you do silicon and then you put some silicon oxide and then you put some more silicon.

2443
02:11:43.337 --> 02:11:46.280
Or you put silicon and then germanium and then you put some more silicon.

2444
02:11:46.560 --> 02:11:50.525
Some kind of heterostructure that makes the electrons want to live directly.

2445
02:11:50.807 --> 02:12:15.362
in a plane everyone wants to live on the second floor of the apartment not the third fourth and fifth yeah not the first but for whatever reason yeah for whatever reason we all want to live on the second floor we all want to live on the second floor now crucially that means that one dimension of confinement has already been taken care of because of the material it at the architecture level we've already confined the system to some variable we know yeah right so

2446
02:12:16.181 --> 02:12:25.588
What that means is I only need to confine it now in these two dimensions into this spot and this spot and this spot and this spot, kind of like a chess checkerboard.

2447
02:12:26.769 --> 02:12:32.694
As opposed to when we talked about trapped ions and neutral atoms, they're in a 3D, three-dimensional space.

2448
02:12:32.734 --> 02:12:36.217
So the complexity of maintaining, you know,

2449
02:12:36.737 --> 02:12:40.740
X, Y, and Z, pun intended, is significantly more difficult.

2450
02:12:40.760 --> 02:12:41.160
Exactly.

2451
02:12:41.240 --> 02:12:42.601
Specifically with trapped ions, right?

2452
02:12:42.621 --> 02:12:44.222
Because they're kind of related to electrons.

2453
02:12:44.262 --> 02:12:46.484
Electrons have charge, just like trapped ions.

2454
02:12:46.924 --> 02:12:54.990
And one of the fundamental theorems that you learn about in undergrad electromagnetism is this idea that a static electric...

2455
02:12:55.590 --> 02:12:57.972
field cannot confine you in three dimensions.

2456
02:12:58.012 --> 02:13:01.134
That's why the trapped ions needed that rotating saddle.

2457
02:13:01.734 --> 02:13:04.216
But here, I've already got 1D confinement.

2458
02:13:04.837 --> 02:13:09.300
And so in order to confine in 2D, I can use static electric fields.

2459
02:13:09.860 --> 02:13:10.140
Right?

2460
02:13:10.180 --> 02:13:11.001
I don't need to...

2461
02:13:12.215 --> 02:13:15.176
oscillate stuff in order to localize the charge here.

2462
02:13:15.296 --> 02:13:17.036
We don't need a harmonic oscillator?

2463
02:13:17.256 --> 02:13:17.476
No.

2464
02:13:17.816 --> 02:13:18.517
That's quite nice.

2465
02:13:18.537 --> 02:13:19.177
That's quite nice.

2466
02:13:19.697 --> 02:13:20.797
No harmonic oscillator.

2467
02:13:20.817 --> 02:13:22.317
Well, there's still going to be a harmonic oscillator.

2468
02:13:22.337 --> 02:13:23.558
But like... You know what I mean.

2469
02:13:23.578 --> 02:13:24.058
I know what you mean.

2470
02:13:24.078 --> 02:13:25.078
I know what you mean.

2471
02:13:25.438 --> 02:13:29.799
So what we can do there, and if you could bring up that... For 59 again?

2472
02:13:29.919 --> 02:13:30.139
Yeah.

2473
02:13:30.539 --> 02:13:31.520
If you could bring that up.

2474
02:13:31.640 --> 02:13:34.080
So you're confining it into 2D.

2475
02:13:34.380 --> 02:13:34.640
Okay.

2476
02:13:34.820 --> 02:13:41.422
And now what you can do is in the 2D, you can create an egg carton potential landscape.

2477
02:13:42.162 --> 02:13:47.626
Okay, for example, you can have an electrode, like a little wire that goes up top here, pops down.

2478
02:13:48.387 --> 02:13:56.313
On the left, you see an electron microscope of all of these wires that are going down from all these places, and that are going to plop down at a certain spot.

2479
02:13:56.794 --> 02:14:06.742
I can have the wire go down, maintain that wire at plus 5 volts, have another wire right next to it that goes down, maintain that wire at negative 5 volts,

2480
02:14:07.303 --> 02:14:10.424
right next to it, plus 5 volts, negative 5 volts, or millivolts or whatever.

2481
02:14:11.544 --> 02:14:12.685
The idea is not the scale.

2482
02:14:12.725 --> 02:14:20.447
The idea is that the sine I can switch such that I create a mountain and a valley and a mountain and a valley.

2483
02:14:20.908 --> 02:14:23.769
And all of the electrons are going to want to sit at the valley.

2484
02:14:25.129 --> 02:14:28.150
And so now I've got a way to confine single electrons.

2485
02:14:29.170 --> 02:14:29.410
Okay?

2486
02:14:29.651 --> 02:14:30.231
That's the idea.

2487
02:14:30.371 --> 02:14:30.691
Okay.

2488
02:14:31.811 --> 02:14:33.892
Okay, so all of these electrons are now confined to...

2489
02:14:34.720 --> 02:14:38.663
in these single electron wells is what we would call it.

2490
02:14:38.823 --> 02:14:41.245
Because we've been able to confine everything to floor two.

2491
02:14:41.825 --> 02:14:49.770
And then we have these electrons rooms that, that we can basically decide which has a two story on the second floor.

2492
02:14:50.271 --> 02:14:52.913
And we can just turn off the two story second floor room or not.

2493
02:14:53.093 --> 02:14:53.433
Or not.

2494
02:14:53.693 --> 02:14:54.294
That's very good.

2495
02:14:54.454 --> 02:14:55.274
Yeah.

2496
02:14:55.434 --> 02:15:00.538
And yeah, it's like we can open the door to the room or not based on like the, the voltage that's coming in.

2497
02:15:00.818 --> 02:15:01.759
right?

2498
02:15:01.919 --> 02:15:09.985
The qubit itself in the, in the original proposal, the lost even Chenzo proposal in that original proposal, the qubit itself was the spins of individual electrons.

2499
02:15:10.526 --> 02:15:12.467
So you can split them up using a magnetic field.

2500
02:15:12.487 --> 02:15:16.691
Like if the spin is this way and then the one neighboring, it is also spinning in one direction.

2501
02:15:16.991 --> 02:15:18.832
You can split them up with a magnetic field.

2502
02:15:19.993 --> 02:15:21.734
And how do you talk to the qubits?

2503
02:15:21.754 --> 02:15:23.676
How do you talk to these like LD qubits?

2504
02:15:23.696 --> 02:15:25.597
You apply a microwave magnetic field.

2505
02:15:25.958 --> 02:15:27.919
That's going to switch them from one spin to another.

2506
02:15:29.060 --> 02:15:37.869
And you can make them talk to each other by simply lowering the voltage barrier between two adjacent spins.

2507
02:15:38.450 --> 02:15:43.315
So you've got one electron, let's say, in this egg depression.

2508
02:15:43.475 --> 02:15:47.579
And then the one right next to it, there's a barrier in between that's keeping them separate.

2509
02:15:48.080 --> 02:15:50.682
If you want them to talk to each other, just lower the barrier.

2510
02:15:50.883 --> 02:15:51.023
Mm-hmm.

2511
02:15:51.343 --> 02:15:51.523
Right.

2512
02:15:51.744 --> 02:15:54.728
There's a, there's a little electrode that is maintaining that barrier.

2513
02:15:54.748 --> 02:15:57.051
It goes negative five volts, positive five volts, negative five volts.

2514
02:15:57.111 --> 02:16:02.579
Actually it's opposite because electrons have negative charge, but whatever, whatever that barrier is, just lower it.

2515
02:16:03.100 --> 02:16:06.405
And now the electrons mush together and they can talk to one another.

2516
02:16:06.525 --> 02:16:10.046
Would it be like in those hotels where they have the two doors on each side of the hotel room?

2517
02:16:10.106 --> 02:16:11.006
And you just open that door.

2518
02:16:11.066 --> 02:16:12.126
Yeah, you just open that door.

2519
02:16:12.226 --> 02:16:12.706
To allow them.

2520
02:16:12.826 --> 02:16:15.607
So it's like the first level is like opening the door to get into the room.

2521
02:16:15.627 --> 02:16:17.787
The second level, which is creating the well.

2522
02:16:18.227 --> 02:16:22.468
And the second level is the door in between the two wells, like the hotel room, to allow them to communicate.

2523
02:16:22.548 --> 02:16:23.248
Exactly.

2524
02:16:23.308 --> 02:16:25.128
And that's called the exchange interaction.

2525
02:16:25.248 --> 02:16:25.768
Okay.

2526
02:16:26.268 --> 02:16:30.569
It was first proposed by Heisenberg when he was trying to talk about magnetic fields.

2527
02:16:30.629 --> 02:16:33.830
But here's the idea with the exchange interaction and why that works so well.

2528
02:16:34.250 --> 02:16:34.610
First...

2529
02:16:35.630 --> 02:16:37.011
It is a DC signal.

2530
02:16:38.112 --> 02:16:38.373
Okay.

2531
02:16:38.933 --> 02:16:42.897
It's just DC voltage where I'm like setting the voltage to this and then I'm moving.

2532
02:16:43.157 --> 02:16:46.259
There's no oscillating stuff that's happening, right?

2533
02:16:46.400 --> 02:16:48.301
When I want the electrons to talk to one another.

2534
02:16:48.922 --> 02:16:56.128
And that exchange interaction is really, um, the way it works is it sounds kind of like a magnet magnetism interaction.

2535
02:16:56.148 --> 02:17:01.012
Like, you know, if you have two bar magnets that are aligned the same way, they're going to kind of repel one another.

2536
02:17:01.032 --> 02:17:01.773
Um, yeah.

2537
02:17:03.518 --> 02:17:13.423
Quantum mechanically, it's not really a magnetic interaction, so much so as it's really electrostatics, like the electrons don't want to be next to each other because they're both negatively charged.

2538
02:17:14.164 --> 02:17:21.628
And there's a Pauli exclusion principle that's happening where if the two electrons are spinning in the same direction...

2539
02:17:22.698 --> 02:17:26.479
If they have the same spin, they're not going to want to be close to one another.

2540
02:17:26.819 --> 02:17:30.261
But if they're spinning in the opposite direction, they're okay being close to one another.

2541
02:17:30.641 --> 02:17:34.342
Because they have opposite spins, and this is how the periodic table works.

2542
02:17:34.382 --> 02:17:40.684
This is why there's two for every energy state, every angular momentum state.

2543
02:17:41.004 --> 02:17:44.725
You populate it one this way, and then you put the next electron in the down state.

2544
02:17:45.046 --> 02:17:49.267
So one up state, one down state, and then you populate the periodic table that way.

2545
02:17:52.168 --> 02:17:56.070
The electrons want to be close to one another only if they have opposite spin.

2546
02:17:56.731 --> 02:18:06.936
If you have this whole, in this hotel room analogy, I don't mean to keep making this dumb, but like if you have a soccer tournament and you have two teams, the door opens, you have red team and blue team, right?

2547
02:18:07.317 --> 02:18:11.539
If the door opens between red team and blue team, they're not going to want to talk to each other because they're on opposite teams.

2548
02:18:11.819 --> 02:18:15.141
But if you have between red team and red team, again, in this analogy, they're going to want to talk to each other.

2549
02:18:15.201 --> 02:18:18.823
It'll be somehow opposite because what I'm saying is the electrons are opposite.

2550
02:18:19.003 --> 02:18:20.064
They want to talk to one another.

2551
02:18:20.084 --> 02:18:20.604
So fair enough.

2552
02:18:20.664 --> 02:18:21.665
So maybe they want to fight.

2553
02:18:21.785 --> 02:18:24.448
The red team and the blue team.

2554
02:18:24.548 --> 02:18:25.589
Everyone's agitated.

2555
02:18:25.609 --> 02:18:26.150
They want to get.

2556
02:18:26.410 --> 02:18:27.551
So and I know.

2557
02:18:27.651 --> 02:18:29.853
They'll keep their space if they're the same team.

2558
02:18:29.913 --> 02:18:39.043
I'm mixing metaphors here because I know your point that you're saying that the energy, it's the positive or negative or the spin one versus another direction.

2559
02:18:39.063 --> 02:18:41.225
And so if it's the same, they're not going to want to.

2560
02:18:41.265 --> 02:18:41.425
Yeah.

2561
02:18:41.545 --> 02:18:45.586
And so in the analogy I'm talking about, you know, red and red and blue and blue are not going to want to.

2562
02:18:46.686 --> 02:18:50.567
But if they're opposite colors, they will want to exchange words.

2563
02:18:50.868 --> 02:18:51.268
Banter.

2564
02:18:51.528 --> 02:18:51.968
Banter.

2565
02:18:52.028 --> 02:18:52.388
Yeah.

2566
02:18:52.408 --> 02:18:54.889
Let's say it's the banter gate.

2567
02:18:56.209 --> 02:19:00.510
And so if they're opposite colors, they're going to want to jaw at each other.

2568
02:19:00.750 --> 02:19:03.991
But again, just to keep – try to simplify that.

2569
02:19:04.551 --> 02:19:07.872
There's the complexities about how those spin states exist.

2570
02:19:07.892 --> 02:19:10.593
But I think part of the point we're getting at is like we –

2571
02:19:12.028 --> 02:19:17.332
Just like every other system we've talked about, you have the potential well has...

2572
02:19:18.373 --> 02:19:20.454
The entanglement state has two...

2573
02:19:21.095 --> 02:19:29.721
The zero and one is very well defined by the dynamics of spin in these systems as has already existed and is well defined.

2574
02:19:29.741 --> 02:19:30.502
Yes, yeah.

2575
02:19:30.642 --> 02:19:34.004
We understand electrons and how they interact with one another very, very well.

2576
02:19:34.044 --> 02:19:34.424
It's no problem.

2577
02:19:34.444 --> 02:19:39.448
And so if we can create these electron wells where they're sitting and we can move them around...

2578
02:19:39.986 --> 02:19:51.169
in these wells and make them talk to one another, we've got a very good handle on how these electrons will talk to one another, how those spins will change as they talk to one another, and so on and so forth.

2579
02:19:51.649 --> 02:19:52.549
How do we read them out?

2580
02:19:52.849 --> 02:19:53.869
Okay, you're right.

2581
02:19:54.509 --> 02:19:54.709
Right?

2582
02:19:55.349 --> 02:19:58.990
Like, how do I tell if the electron is spinning one way or the other way?

2583
02:19:59.250 --> 02:20:03.291
Because we know we understand how these things could, but then how do we see that they are?

2584
02:20:03.471 --> 02:20:03.891
Exactly.

2585
02:20:03.931 --> 02:20:06.492
Like, with the superconducting circuits, there was a resonator,

2586
02:20:06.932 --> 02:20:12.876
that if it's in a zero or one, it would resonate with that microwave cavity, and then I'd be able to read it out, whether it's one way or the other.

2587
02:20:13.476 --> 02:20:17.178
With ions and with neutral atoms, you basically just image them in some sense.

2588
02:20:17.198 --> 02:20:21.861
You, like, use a laser and you try to image the light that comes out.

2589
02:20:22.321 --> 02:20:26.084
Now, with spins, it's a little bit tricky, right?

2590
02:20:26.104 --> 02:20:29.666
Because I don't have direct access to which way they're spinning.

2591
02:20:29.686 --> 02:20:30.146
Okay.

2592
02:20:30.506 --> 02:20:32.708
But from the dynamics that I just told you...

2593
02:20:34.165 --> 02:20:42.427
If they're both spinning in the same direction or if they're spinning in opposite directions, I'm using this very colloquially in some sense.

2594
02:20:42.527 --> 02:20:48.689
Because usually it's like the spin states are not just straight this and this or this.

2595
02:20:49.789 --> 02:20:51.210
There's combinations between them.

2596
02:20:51.230 --> 02:20:57.151
There's something called the singlet state and the triplet state, which is the spins going this way and this way.

2597
02:20:57.211 --> 02:20:59.172
You either add them up or you subtract them.

2598
02:21:00.072 --> 02:21:03.556
And those are the two states that are zeros and ones.

2599
02:21:03.957 --> 02:21:09.803
But the dynamics that I told you earlier about how they want to be together or not is still the same.

2600
02:21:10.143 --> 02:21:14.588
If they're in the singlet state, then they have no problem being in a single state.

2601
02:21:15.377 --> 02:21:15.717
Spot.

2602
02:21:16.277 --> 02:21:19.799
If they're in the triplet state, they have a problem being in the same spot.

2603
02:21:20.299 --> 02:21:26.522
OK, because of the Pauli exclusion principle is part of what you're saying that what puts them in the singlet or triplet state is a lot of options.

2604
02:21:26.582 --> 02:21:28.683
Yeah, there's it's not just up or down.

2605
02:21:28.743 --> 02:21:28.963
Yeah.

2606
02:21:29.403 --> 02:21:33.585
But to simplify like two options, but like it doesn't matter for this discussion.

2607
02:21:33.625 --> 02:21:33.925
For sure.

2608
02:21:33.985 --> 02:21:35.846
What matters is that those are the two states.

2609
02:21:35.966 --> 02:21:36.186
Yes.

2610
02:21:36.567 --> 02:21:36.747
And.

2611
02:21:37.487 --> 02:21:46.029
For the singlet state, the Pauli exclusion principle lets them hang out in the same spot, but the triplet state, it does not let them hang out in the same spot.

2612
02:21:46.089 --> 02:21:58.673
So now what you can do is if I have two wells, and now I raise one of them so that I try to put both of the electrons in the same room, if they're in the singlet state, it's going to be way easier for them to get into the same room.

2613
02:21:59.013 --> 02:22:01.814
But if they're in the triplet state, they're not going to want to get into the same room.

2614
02:22:01.954 --> 02:22:03.254
It's going to take a lot more time.

2615
02:22:04.175 --> 02:22:05.055
And if I sense...

2616
02:22:06.191 --> 02:22:17.636
whether there are two electrons or just one electron in that room that I tried to shove everyone in, then I've got a readout mechanism to tell whether I'm in the zero or the one, whether I'm in a singlet or a triplet.

2617
02:22:17.916 --> 02:22:18.756
That's what's happening here.

2618
02:22:18.816 --> 02:22:23.558
So on the top, you've got kind of a triplet state in the sense that the electrons are not aligned.

2619
02:22:24.038 --> 02:22:25.819
And when I try to...

2620
02:22:26.179 --> 02:22:27.099
They are not aligned, right.

2621
02:22:27.159 --> 02:22:31.541
And so in the singlet state, when they're not aligned, if I try to shove them into one, it's allowed.

2622
02:22:32.222 --> 02:22:33.262
But if they're in the same...

2623
02:22:34.393 --> 02:22:38.563
then when I try to shove them, it kind of gets blocked because the electrons don't want to talk to one another.

2624
02:22:38.904 --> 02:22:42.473
And the point is, if I can tell what the charge is,

2625
02:22:43.327 --> 02:22:48.708
If there's two electrons in that second room or just one, then I can tell whether it was in the zero or the one.

2626
02:22:48.748 --> 02:22:50.128
And that's my readout mechanism.

2627
02:22:50.729 --> 02:22:53.829
So you basically do something to change the environment.

2628
02:22:54.289 --> 02:22:59.230
And then when you look at it, if the two electrons are together, then you know it's zero.

2629
02:22:59.370 --> 02:23:00.911
If they're not, then you know it's a one.

2630
02:23:00.931 --> 02:23:01.871
Then it's a no.

2631
02:23:02.351 --> 02:23:07.712
To keep my annoying analogy together, in the movie Inception, when the hotel room started rotating...

2632
02:23:08.052 --> 02:23:13.458
If when it started rotating, the electron moved into the room, then you have your zero.

2633
02:23:13.618 --> 02:23:21.547
If for whatever reason it was sticking to the wall and refusing to go into the room when the whole hallway was rotating, you're in your one state here.

2634
02:23:21.787 --> 02:23:22.248
Exactly.

2635
02:23:23.830 --> 02:23:25.932
Now, this introduces a caveat, though.

2636
02:23:25.952 --> 02:23:29.436
It's kind of magical that we can even tell that there are two electrons floating.

2637
02:23:30.475 --> 02:23:31.576
In the room in the first place.

2638
02:23:31.736 --> 02:23:32.316
In the well.

2639
02:23:32.397 --> 02:23:32.577
Right?

2640
02:23:32.617 --> 02:23:37.861
Like, how do I tell if there's two electrons there or one electron's there?

2641
02:23:38.161 --> 02:23:38.341
Right?

2642
02:23:38.381 --> 02:23:41.784
Like, imagine, again, this is a solid state, like, piece of metal.

2643
02:23:42.424 --> 02:23:45.387
It's a piece of metal where we've confined it single electrons.

2644
02:23:46.928 --> 02:23:48.789
I need to know where the electrons are.

2645
02:23:49.990 --> 02:23:50.191
Yeah.

2646
02:23:50.891 --> 02:23:51.412
In a metal.

2647
02:23:51.652 --> 02:23:51.752
Yeah.

2648
02:23:51.772 --> 02:23:51.932
Yeah.

2649
02:23:53.307 --> 02:23:55.150
There's a lot of electrons everywhere.

2650
02:23:55.170 --> 02:23:56.532
Yeah, I was going to say, which one?

2651
02:23:56.872 --> 02:23:57.052
Right?

2652
02:23:57.112 --> 02:24:01.879
Like, how do I tell where the electron is and how many there are and so on and so forth?

2653
02:24:02.399 --> 02:24:02.620
Okay.

2654
02:24:03.261 --> 02:24:07.426
So to actually see the thing, I mean, we're talking about single electrons again, right?

2655
02:24:07.446 --> 02:24:10.230
You can't use the resonant cavities and you can't use the lasers.

2656
02:24:10.250 --> 02:24:10.370
Right.

2657
02:24:10.922 --> 02:24:11.782
and all that other stuff.

2658
02:24:11.842 --> 02:24:13.383
Oh, no lasers.

2659
02:24:13.603 --> 02:24:16.784
Instead, we used something called a single electron transistor.

2660
02:24:16.824 --> 02:24:22.586
This was one of the coolest things that I had to get used to once I was getting involved in this project.

2661
02:24:22.626 --> 02:24:24.526
A single electron transistor?

2662
02:24:24.626 --> 02:24:26.907
Yeah, it's such a cool-sounding thing, right?

2663
02:24:27.787 --> 02:24:28.147
Okay.

2664
02:24:28.328 --> 02:24:30.208
So here's how a normal transistor works.

2665
02:24:30.588 --> 02:24:36.050
There's a source and a drain, and if there's current flowing between the source and the drain...

2666
02:24:36.403 --> 02:24:37.084
that's your one.

2667
02:24:37.184 --> 02:24:40.287
And if the current is not flowing in your source and drain, that's a zero.

2668
02:24:40.547 --> 02:24:48.255
And the way you make the current flow is you control the gate, the voltage on the gate, and you lower the barrier.

2669
02:24:48.896 --> 02:24:50.998
If you lower the barrier enough, there's a bunch of current.

2670
02:24:51.138 --> 02:24:54.341
If you don't lower the barrier enough, there's a barrier, and it stops the current.

2671
02:24:54.501 --> 02:24:55.542
That's how transistors work.

2672
02:24:55.622 --> 02:24:56.023
Yeah, yeah, yeah.

2673
02:24:56.964 --> 02:24:58.085
Now, there's going to be a point...

2674
02:24:59.810 --> 02:25:13.818
If you manufacture this stuff so cleanly and so closely, such that there's a source electrode and a gate electrode that are right next to each other, maybe a few nanometers, tens of nanometers apart.

2675
02:25:14.158 --> 02:25:17.560
You've also got a little gate in the middle that controls that voltage.

2676
02:25:18.741 --> 02:25:23.424
If you lower the gate just enough, single electrons...

2677
02:25:24.267 --> 02:25:26.628
are going to go through on the left-hand side.

2678
02:25:26.648 --> 02:25:27.548
You slaver dog.

2679
02:25:27.588 --> 02:25:28.048
I see it.

2680
02:25:28.148 --> 02:25:28.388
Yep.

2681
02:25:28.648 --> 02:25:28.828
Right?

2682
02:25:28.849 --> 02:25:29.029
I get it.

2683
02:25:29.049 --> 02:25:29.609
Yeah, I get it.

2684
02:25:30.029 --> 02:25:36.151
Basically, you're just creating a gap that's only the size of literally the shell of an electron.

2685
02:25:36.171 --> 02:25:42.473
Yeah, this is a review paper that was actually written by Michel DeVore, who is one of the Nobel Prizes.

2686
02:25:43.248 --> 02:25:43.708
last year.

2687
02:25:43.768 --> 02:25:45.289
Yeah, that's quite nice.

2688
02:25:45.349 --> 02:25:47.590
He's been working in quantum tech for a long time.

2689
02:25:47.630 --> 02:25:51.873
And he's saying you can amplify quantum signals using the single electron transistor.

2690
02:25:51.913 --> 02:25:52.553
Here's the idea.

2691
02:25:53.033 --> 02:25:56.796
If I've now got this sensor, this is effectively a sensor.

2692
02:25:57.376 --> 02:25:57.556
Right.

2693
02:25:57.956 --> 02:26:02.919
I've got a little single electron transistor that is moving these electrons from one spot to another.

2694
02:26:04.725 --> 02:26:10.030
If now I start changing the environment in my device, right?

2695
02:26:10.170 --> 02:26:17.756
The rooms, let's say your hotel rooms, are all on the... Let's say there's a lot... You know where the elevators are on the second floor?

2696
02:26:17.776 --> 02:26:18.036
Yeah, yeah.

2697
02:26:18.257 --> 02:26:18.417
Right?

2698
02:26:18.457 --> 02:26:21.219
Let's say those elevators are where the single electron transistor is.

2699
02:26:21.419 --> 02:26:21.559
Okay.

2700
02:26:21.579 --> 02:26:21.800
Right?

2701
02:26:21.820 --> 02:26:23.921
You've got a source elevator and a drain elevator.

2702
02:26:23.941 --> 02:26:24.162
Yeah, yeah.

2703
02:26:24.382 --> 02:26:28.405
And you've got this like shuttling that's happening, right?

2704
02:26:28.846 --> 02:26:32.809
If the rooms start moving around with electrons...

2705
02:26:34.339 --> 02:26:46.642
the electron that is doing this single transistor effect is going to feel the effect because this is negatively charged and all the other electrons are close by and negatively charged.

2706
02:26:46.782 --> 02:26:58.365
And if I can sense that current very precisely, I can get little tiny deflections, little blips, whenever the states in the rooms change.

2707
02:26:58.565 --> 02:27:02.926
So by watching my single electron transistor very precisely,

2708
02:27:04.147 --> 02:27:07.209
I can tell all of the stuff that is happening on the second floor.

2709
02:27:07.550 --> 02:27:11.693
Would it be almost like hearing footsteps when you're in the elevator of someone running up and down the hallway?

2710
02:27:11.913 --> 02:27:12.233
Kind of.

2711
02:27:12.273 --> 02:27:12.994
Yeah, yeah.

2712
02:27:13.034 --> 02:27:13.454
Exactly.

2713
02:27:13.494 --> 02:27:20.900
Like the idea that you can sense at distance something that's happening from your single electron transistor, which is this elevator shaft.

2714
02:27:20.920 --> 02:27:23.241
Again, trying to create a very crude analogy here.

2715
02:27:23.622 --> 02:27:27.885
But effectively, that's what we're trying to say.

2716
02:27:28.025 --> 02:27:31.347
You can sense what's happening in these wells, these potential wells.

2717
02:27:31.367 --> 02:27:32.048
Yeah.

2718
02:27:32.268 --> 02:27:51.633
at distance because the charge of what's happening in the wells will impact the electron gate that you have yeah that you're sensitive that you have is your sensor yeah exactly so i've got a sensor right here and that's like got a little tiny bit of current that i'm sensitive to and as the electrons move around in my device

2719
02:27:52.673 --> 02:27:54.594
This thing is going to start changing.

2720
02:27:54.654 --> 02:27:55.194
It'll jiggle.

2721
02:27:55.414 --> 02:27:55.975
It'll jiggle.

2722
02:27:56.095 --> 02:28:03.838
And if I'm sensitive to that jiggle and I know my physics well enough about what each jiggle represents, I can tell what's happening everywhere.

2723
02:28:03.858 --> 02:28:06.259
You can translate it into position of all of the... Yeah.

2724
02:28:06.499 --> 02:28:06.699
Okay.

2725
02:28:06.719 --> 02:28:07.920
It's kind of...

2726
02:28:07.980 --> 02:28:14.223
When I first got my hands on one of these devices and I was like, you know, I had a single... Like I made a...

2727
02:28:14.723 --> 02:28:17.226
call it a charge sensor or a single SET.

2728
02:28:17.747 --> 02:28:21.171
It's just, it's so cool to think that that's what you're doing.

2729
02:28:21.972 --> 02:28:25.957
It was one of those moments, I think like in my life when I was like, this is like really cool.

2730
02:28:25.997 --> 02:28:33.146
That's really, I'm watching like single electrons move around from one compartment to the another on this nano fabricated device.

2731
02:28:34.053 --> 02:28:35.254
That's been fabricated.

2732
02:28:35.274 --> 02:28:35.534
Yeah.

2733
02:28:35.614 --> 02:28:35.834
Yeah.

2734
02:28:35.854 --> 02:28:37.035
It's, it's, it's really cool.

2735
02:28:37.055 --> 02:28:39.577
I mean, it's like you're, you're sensing quantum stuff.

2736
02:28:39.737 --> 02:28:39.937
Yeah.

2737
02:28:40.498 --> 02:28:40.678
Right.

2738
02:28:40.698 --> 02:28:41.318
That's happening.

2739
02:28:41.559 --> 02:28:41.739
Yeah.

2740
02:28:42.139 --> 02:28:42.819
Yeah.

2741
02:28:42.880 --> 02:28:43.440
That's quite nice.

2742
02:28:43.700 --> 02:28:44.381
It was really cool.

2743
02:28:44.401 --> 02:28:48.404
I still, I will never forget the day that I had my first SET.

2744
02:28:48.804 --> 02:28:52.327
I made my first SET and then I saw like my first tunneling event and things like that.

2745
02:28:52.347 --> 02:28:53.227
It was, it was really cool.

2746
02:28:53.848 --> 02:28:54.048
Um,

2747
02:28:54.940 --> 02:29:05.164
So that's one way to implement it, which is, in this case, every single electron that's in my checkerboard, eggshell, whatever you want to call it, is a single qubit, right?

2748
02:29:05.204 --> 02:29:08.165
It's either spinning one way or it's spinning the other way based on a magnetic field.

2749
02:29:08.225 --> 02:29:10.526
I talk to it based on microwave frequencies.

2750
02:29:10.827 --> 02:29:16.229
Now, there's an argument to be made that, like, you don't want any microwaves whatsoever, right?

2751
02:29:16.329 --> 02:29:23.692
Even you could have just a single microwave that's talking to these guys, and then you can tune all of them based on the single microwave.

2752
02:29:24.212 --> 02:29:26.933
But what if you don't want any microwaves whatsoever?

2753
02:29:28.353 --> 02:29:32.674
What if all I want to do is lower the barriers?

2754
02:29:33.954 --> 02:29:34.254
Okay?

2755
02:29:34.334 --> 02:29:36.135
That's all I want to do is exchange.

2756
02:29:36.475 --> 02:29:37.815
Open the doors between the hotel rooms.

2757
02:29:37.835 --> 02:29:38.095
Yeah.

2758
02:29:38.175 --> 02:29:40.856
Remember, before the exchange was for two qubit gates.

2759
02:29:41.176 --> 02:29:41.396
Yes.

2760
02:29:42.056 --> 02:29:45.637
But in order to do one qubit flipping, I still needed the microwave.

2761
02:29:45.737 --> 02:29:45.837
Yeah.

2762
02:29:45.857 --> 02:29:47.257
And I still needed the magnetic field.

2763
02:29:47.337 --> 02:29:47.517
Yeah.

2764
02:29:47.597 --> 02:29:50.678
What if I want to do everything based on just opening and closing doors?

2765
02:29:50.998 --> 02:29:51.218
Mm-hmm.

2766
02:29:52.292 --> 02:30:01.254
So DiVincenzo came up in 2000 with this Nature paper, along with a bunch of his colleagues, with the exchange-only qubit.

2767
02:30:02.194 --> 02:30:02.435
Okay?

2768
02:30:02.875 --> 02:30:12.097
This is a qubit where both single-qubit gates and two-qubit gates are mediated only by the exchange interaction.

2769
02:30:13.451 --> 02:30:20.198
Meaning we now no longer need two separate basically vehicles for interacting with this or controlling the system.

2770
02:30:20.238 --> 02:30:20.458
Yeah.

2771
02:30:20.578 --> 02:30:27.705
That are almost related but independent variables that when you come to like the experimental apparatus –

2772
02:30:28.452 --> 02:30:30.152
like need to be controlled in different ways.

2773
02:30:30.172 --> 02:30:30.893
Yeah, and maybe it's better.

2774
02:30:31.013 --> 02:30:35.074
Maybe it's better if there's just only one thing we do, which is just exchange, it's all DC.

2775
02:30:35.174 --> 02:30:36.314
It's one thing to handle.

2776
02:30:36.494 --> 02:30:38.315
There's no microwave signal that's going in.

2777
02:30:38.375 --> 02:30:40.435
It's only one thing that we gotta get really, really good at.

2778
02:30:40.715 --> 02:30:40.915
Right.

2779
02:30:41.115 --> 02:30:41.656
Which is ideal.

2780
02:30:41.896 --> 02:30:42.116
Yeah.

2781
02:30:42.376 --> 02:30:49.258
The caveat though, is that now your qubit is not a single electron.

2782
02:30:50.158 --> 02:30:54.219
You need three electrons in entangled states.

2783
02:30:55.340 --> 02:30:59.644
And then you can now have a singlet and a triplet be your zero and one.

2784
02:30:59.684 --> 02:31:02.166
Before it's like this was a zero and one.

2785
02:31:02.206 --> 02:31:04.648
Now it's like this is your zero.

2786
02:31:04.988 --> 02:31:07.430
And then another set of spins is your one.

2787
02:31:07.731 --> 02:31:08.051
Okay.

2788
02:31:08.231 --> 02:31:08.491
Okay.

2789
02:31:08.912 --> 02:31:11.754
So the caveat is you've made your problem a bit bigger.

2790
02:31:12.415 --> 02:31:15.898
Right now, instead of a single electron, you're worried about three electrons at a time.

2791
02:31:16.398 --> 02:31:18.640
Because that's what's required to give you a zero.

2792
02:31:19.040 --> 02:31:19.741
That's the trade-off.

2793
02:31:20.281 --> 02:31:21.663
That's the trade-off.

2794
02:31:21.883 --> 02:31:22.043
And...

2795
02:31:23.632 --> 02:31:29.344
This is where the exchange-only interaction comes in, and this exchange-only qubit.

2796
02:31:29.825 --> 02:31:30.948
Three electrons now.

2797
02:31:31.469 --> 02:31:31.649
Yeah.

2798
02:31:32.070 --> 02:31:32.210
Okay?

2799
02:31:32.230 --> 02:31:32.431
Okay.

2800
02:31:33.987 --> 02:31:44.473
The first two, whether the first two are in a singlet or a triplet state, these two different spin states that we don't have to worry about for this episode, that's going to be your zero and one.

2801
02:31:45.354 --> 02:31:45.594
Okay.

2802
02:31:46.415 --> 02:31:46.595
Okay?

2803
02:31:47.155 --> 02:31:57.321
And the third electron is there to give you full qubit control on the block sphere, meaning, like, you know, for a full qubit, I need to be able to rotate on two axes, right?

2804
02:31:57.381 --> 02:32:00.083
I need to access this, and I need to access every longitude.

2805
02:32:00.103 --> 02:32:00.243
Okay.

2806
02:32:00.383 --> 02:32:01.164
And every latitude.

2807
02:32:01.544 --> 02:32:07.151
And so the exchange on the first two is going to let you rotate on the north-south.

2808
02:32:07.191 --> 02:32:07.331
Yeah.

2809
02:32:07.491 --> 02:32:08.112
Yep.

2810
02:32:08.132 --> 02:32:13.578
And the exchange on the second two, two and three, is going to let you rotate somewhere near the equator.

2811
02:32:13.618 --> 02:32:20.846
Not actually at the equator, but somewhere off the equator, just based on how the algebra of the space works out.

2812
02:32:21.507 --> 02:32:22.207
This is interesting.

2813
02:32:22.247 --> 02:32:31.209
And so it requires three electrons now to basically define the two states of zero and one.

2814
02:32:31.369 --> 02:32:31.569
Yep.

2815
02:32:31.809 --> 02:32:36.630
Based on how the first two of those three interact versus the second two of those three interact.

2816
02:32:36.670 --> 02:32:36.870
Yeah.

2817
02:32:37.191 --> 02:32:40.911
And so we're basically deriving two states from a three-body system.

2818
02:32:40.931 --> 02:32:41.151
Yes.

2819
02:32:41.531 --> 02:32:48.193
Now, with the three-body system, right, there's actually one – there's another advantage here.

2820
02:32:48.473 --> 02:32:52.014
So the first advantage I've already told you, which is that everything is DC.

2821
02:32:52.094 --> 02:32:55.856
All you have to do is lower the barriers in between them.

2822
02:32:55.896 --> 02:32:57.336
So everything is DC control.

2823
02:32:58.117 --> 02:33:04.159
So you don't have to worry about like AC oscillating, electromagnetic fields, and all that other kind of crap going in.

2824
02:33:04.379 --> 02:33:12.282
The other thing is that because there's three, the algebra also works out such that you are insensitive to...

2825
02:33:12.629 --> 02:33:14.271
to global magnetic fields.

2826
02:33:14.331 --> 02:33:22.018
If there's a giant magnetic field that's going through this, you don't care because all of these spins are rotating in the same way.

2827
02:33:22.098 --> 02:33:27.523
It's kind of like, remember in Interstellar, that scene where they tried to dock with a rotating...

2828
02:33:28.003 --> 02:33:54.641
like spaceship yeah it's like tars we need to we need to match the rotation and then like tars makes the thing spin in a certain way and um whoever who's the actor matthew mcconaughey is like he's like he's like pushing his uh head in the other direction to counteract the g-forces and they're spinning in such a way that they match the rotation and then they can dock similarly in this case like the magnetic field a big magnetic field is going to come in as long as it's the

2829
02:33:56.982 --> 02:34:00.544
Everything is going to rotate in the same way, and your quantum information is going to be preserved.

2830
02:34:00.785 --> 02:34:04.667
And now, because we have that third body in the system, it partly is why.

2831
02:34:05.848 --> 02:34:09.450
That enables...

2832
02:34:09.951 --> 02:34:16.415
The system is large enough locally that a larger external factor is going to impact, but the system still has enough...

2833
02:34:16.923 --> 02:34:24.248
Yeah, there's like an algebra in here that is going to just be invariant to all of the big rotations.

2834
02:34:24.288 --> 02:34:24.488
Yeah.

2835
02:34:24.668 --> 02:34:24.808
Right?

2836
02:34:24.828 --> 02:34:27.610
Crucially, if there's local magnetic fields, that's still a problem.

2837
02:34:27.930 --> 02:34:28.091
Right?

2838
02:34:28.111 --> 02:34:32.654
Like if the third one is rotating in a different way than the first two.

2839
02:34:32.794 --> 02:34:33.334
Still a problem.

2840
02:34:33.354 --> 02:34:34.035
That's still a problem.

2841
02:34:34.055 --> 02:34:37.497
But a global magnetic field, like the Earth's big magnetic field, you don't care about it.

2842
02:34:37.517 --> 02:34:37.797
Not a problem.

2843
02:34:37.817 --> 02:34:42.540
Because it's mostly going to be the same across these three, like a few tens of nanometers.

2844
02:34:42.600 --> 02:34:43.661
So it's like gauge hacking.

2845
02:34:43.761 --> 02:34:44.822
I call it gauge hacking.

2846
02:34:44.842 --> 02:34:44.982
Okay.

2847
02:34:45.611 --> 02:34:47.754
Because there's like a weird gauge theory that happens here.

2848
02:34:48.375 --> 02:34:49.878
Oh, gauge theory made it in.

2849
02:34:49.958 --> 02:34:51.541
Yeah, exactly.

2850
02:34:51.621 --> 02:34:53.464
So that's kind of cool, right?

2851
02:34:53.484 --> 02:34:53.704
Okay.

2852
02:34:54.466 --> 02:34:54.726
Now...

2853
02:34:55.832 --> 02:34:59.333
Why are people initially excited about just spins in general?

2854
02:35:00.034 --> 02:35:12.358
Okay, when DiVincenzo came out in 2000 with this paper, or in 1998 with the first paper, people were excited because silicon is nice, and you can do this in silicon.

2855
02:35:12.798 --> 02:35:16.300
This was a proposal to make a quantum computer in silicon, right?

2856
02:35:16.580 --> 02:35:21.842
Which means I can now leverage all of the silicon manufacturing that humanity has gotten really, really good at.

2857
02:35:21.862 --> 02:35:22.182
Right, right.

2858
02:35:22.762 --> 02:35:24.604
This is a single silicon wafer.

2859
02:35:24.984 --> 02:35:38.754
It's a piece of, I don't know, 99.999999% pure silicon that then you plug through an ASML EUV lithography machine and then you print chips.

2860
02:35:39.114 --> 02:35:40.735
This is where your GPUs come from.

2861
02:35:40.975 --> 02:35:43.737
This is where the chips in your laptop come from.

2862
02:35:43.897 --> 02:35:47.280
Everything is made out of silicon in today's economy.

2863
02:35:48.051 --> 02:36:05.597
And so the idea is this methodology of spin cubit, like, sorry, of what DiVincenzo had come up with at the time, the substrate you could build it on top of did not require lasers, did not require barium, it did not require, what was the other one?

2864
02:36:05.617 --> 02:36:07.958
The Y-savoc.

2865
02:36:09.198 --> 02:36:29.505
the the um neutral atoms yes yes it didn't uterbium uterbium did not require any of these yeah tantalum tantalum yeah like all of that it's just silicon it's just we can and the part of the point here is our entire uh current economy uh yes uh manufacturing based as it relates to computing systems

2866
02:36:30.605 --> 02:36:55.810
are well suited for scaling silicon that's convenient this was in 2000 which it wasn't even at the point where this is that big yet yeah but nowadays it's even more clear exactly or more robust yeah okay so in terms of scalability this seems like already like there's there's there's ways that this could work right sure now why have people been skeptical though yeah because

2867
02:36:56.570 --> 02:37:01.113
Because clearly that guy at Alice and Bob didn't even know about spin qubits.

2868
02:37:01.633 --> 02:37:06.635
And even the big higher-ups who know about spin qubits, they're always like, eh, but probably not.

2869
02:37:07.336 --> 02:37:11.038
There has been good reason for skepticism.

2870
02:37:11.998 --> 02:37:21.583
For one, the fabrication requirement here is difficult because you need to use one of these major fabs that has this...

2871
02:37:21.723 --> 02:37:24.565
So unlike, for example...

2872
02:37:25.548 --> 02:37:33.457
trapped ions on neutral atoms, you can create small qubits, small numbers of qubits, using bespoke physics machinery that is found in the lab.

2873
02:37:33.838 --> 02:37:35.760
Lasers are very common in labs.

2874
02:37:36.741 --> 02:37:43.109
Superconducting circuits, also you can kind of just, like PhD students can make their own because it's the size of a millimeter.

2875
02:37:43.129 --> 02:37:45.592
You can use a light microscope and make stuff.

2876
02:37:46.112 --> 02:37:47.353
With this, you need to fab it.

2877
02:37:47.493 --> 02:37:47.793
Yeah.

2878
02:37:48.013 --> 02:37:53.758
You need a fab that's, like, willing to, you know, be like, okay, let's print this thing.

2879
02:37:54.298 --> 02:37:55.599
So that's difficult.

2880
02:37:55.859 --> 02:37:57.640
You can't just make this in grad school.

2881
02:37:58.641 --> 02:38:02.564
At least not the big, at least you can make, like, big ones in grad school, right?

2882
02:38:04.393 --> 02:38:06.074
And there's certain problems.

2883
02:38:06.114 --> 02:38:08.675
There are like inherent problems that have to be solved.

2884
02:38:08.735 --> 02:38:16.739
For one, I told you about the magnetic field problem, which is that a global magnetic field is fine, but local magnetic fields are a problem.

2885
02:38:17.379 --> 02:38:25.703
Now, silicon, normal silicon, the stuff that's in your computer, has a lot of local magnetic fields because silicon comes in two isotopes.

2886
02:38:26.285 --> 02:38:28.410
It comes in a 28 and a 29.

2887
02:38:29.112 --> 02:38:32.420
That's the number of protons and neutrons in its nucleus.

2888
02:38:32.621 --> 02:38:35.628
With 28, because of the Pauli exclusion principle...

2889
02:38:36.983 --> 02:38:38.664
All of the spins are going to cancel each other.

2890
02:38:38.704 --> 02:38:40.104
That's how they're on top of one another.

2891
02:38:40.625 --> 02:38:43.866
And so there's going to be no net magnetic field inside every single atom.

2892
02:38:43.906 --> 02:38:45.547
But for 29, there's an odd number.

2893
02:38:45.987 --> 02:38:49.729
So there's going to be a tiny magnetic field because of the spin of the nucleus.

2894
02:38:50.449 --> 02:38:51.369
So we want 28.

2895
02:38:51.589 --> 02:38:52.710
We want a lot of 28.

2896
02:38:52.750 --> 02:38:53.850
We don't want a lot of 29.

2897
02:38:54.170 --> 02:38:57.592
But naturally occurring silicon has about 92% 28.

2898
02:38:57.632 --> 02:38:59.333
And for the 29, there's about 5%.

2899
02:39:05.634 --> 02:39:07.216
Now, for normal silicon, that doesn't matter.

2900
02:39:07.236 --> 02:39:09.139
For normal classical computing, it doesn't matter.

2901
02:39:09.179 --> 02:39:12.504
But here, your quantum information is going to be lost.

2902
02:39:12.724 --> 02:39:13.446
There's too much.

2903
02:39:13.646 --> 02:39:13.866
Yeah.

2904
02:39:14.267 --> 02:39:14.507
Okay?

2905
02:39:14.687 --> 02:39:14.988
Okay.

2906
02:39:15.448 --> 02:39:16.270
So that's one reason.

2907
02:39:16.991 --> 02:39:18.313
Charge noise is a thing, right?

2908
02:39:18.373 --> 02:39:20.055
If you have, like, random stray charges...

2909
02:39:20.862 --> 02:39:24.763
your fab isn't good enough or something, then you're going to have some random electromagnetic fields.

2910
02:39:25.303 --> 02:39:26.323
That's going to cause a problem.

2911
02:39:26.363 --> 02:39:29.264
And then finally, there's this demon called the valley splitting.

2912
02:39:29.284 --> 02:39:30.124
Okay?

2913
02:39:30.424 --> 02:39:33.385
This is something that I'm going to be honest, I do not understand.

2914
02:39:33.965 --> 02:39:38.406
I'm also going to be honest, a lot of practitioners in spin qubits don't understand.

2915
02:39:39.086 --> 02:39:45.047
And a lot of the people outside of spin qubits who say that valley splitting is the problem also don't understand.

2916
02:39:45.127 --> 02:39:49.888
It's kind of just this thing where the real theorists are like, yeah, it's clearly a problem.

2917
02:39:52.412 --> 02:39:55.274
here's from what I gather from reading about it, okay?

2918
02:39:55.834 --> 02:39:59.496
The idea is that silicon has this really weird band structure.

2919
02:39:59.937 --> 02:40:11.603
Like, remember, in previous episodes, we talked about the valence band and the conduction band and how the difference between these two is what gives silicon all of its nice properties as a semiconductor.

2920
02:40:12.724 --> 02:40:17.907
Now, part of that band structure means that in bulk silicon...

2921
02:40:18.618 --> 02:40:26.051
The electrons actually can choose to live in one of six different states that all have the same energy.

2922
02:40:26.631 --> 02:40:28.413
For classical computing, this doesn't matter.

2923
02:40:29.014 --> 02:40:32.337
But for quantum computing, we only want two states.

2924
02:40:33.038 --> 02:40:33.318
Okay?

2925
02:40:34.079 --> 02:40:41.266
Which means we only want one of the valley states where the electron can live in either a spin up or a spin down.

2926
02:40:41.827 --> 02:40:47.974
If there's six and in each of them they can live in a spin up or spin down, now all of a sudden I've got 12 different things that I need to worry about.

2927
02:40:48.354 --> 02:40:49.195
I only want two.

2928
02:40:50.785 --> 02:40:51.005
Mm-hmm.

2929
02:40:51.445 --> 02:40:51.705
Okay.

2930
02:40:51.925 --> 02:40:53.186
Yeah.

2931
02:40:53.246 --> 02:40:56.047
This is for us living in the valley.

2932
02:40:56.887 --> 02:41:01.069
There's six different ways to define what is the valley in Los Angeles.

2933
02:41:01.089 --> 02:41:01.309
Yes.

2934
02:41:01.569 --> 02:41:04.090
And we want one way to define what is the valley.

2935
02:41:04.391 --> 02:41:05.891
The valley is Los Angeles.

2936
02:41:05.931 --> 02:41:06.171
Yeah.

2937
02:41:06.371 --> 02:41:09.132
But the problem is part of the valley is in Los Angeles, the city.

2938
02:41:09.573 --> 02:41:11.193
Part of it's not in the city of Los Angeles.

2939
02:41:11.633 --> 02:41:14.935
What we're kind of saying is we just want the part of the valley that's in the city of Los Angeles.

2940
02:41:15.075 --> 02:41:15.175
Yes.

2941
02:41:15.195 --> 02:41:15.315
Yes.

2942
02:41:15.335 --> 02:41:15.495
Exactly.

2943
02:41:16.096 --> 02:41:17.117
And not the other stuff.

2944
02:41:17.157 --> 02:41:17.938
And not the other stuff.

2945
02:41:17.958 --> 02:41:19.099
Not Burbank, Glendale.

2946
02:41:19.139 --> 02:41:19.580
Right, right.

2947
02:41:19.620 --> 02:41:21.582
Not Thousand Oaks and all that.

2948
02:41:21.963 --> 02:41:24.245
However, that's not how it physically is.

2949
02:41:24.265 --> 02:41:24.485
Yeah.

2950
02:41:24.505 --> 02:41:29.071
Physically, all of these, the electrons can't tell the difference between the cities.

2951
02:41:29.311 --> 02:41:29.772
Right, right.

2952
02:41:29.792 --> 02:41:30.993
It's like we're in the valley.

2953
02:41:31.173 --> 02:41:32.435
Oh, it's we're in the valley.

2954
02:41:32.475 --> 02:41:32.915
Exactly.

2955
02:41:33.035 --> 02:41:33.296
Anyway.

2956
02:41:33.436 --> 02:41:35.298
Now, that's in bulk silicon.

2957
02:41:35.318 --> 02:41:35.839
You get six.

2958
02:41:36.379 --> 02:41:56.249
Now, if you do the heterostructure that we've been talking about that confines the electrons into this 2D plane, you put, I don't know, a layer of germanium or something, then that lifts the degeneracy, and now you're only worried about two things, because the two dimensions in X and Y are in one state, the Z dimension, which is the one that has the different symmetries in the other state.

2959
02:41:56.269 --> 02:41:57.209
So now you're worried about two.

2960
02:41:57.729 --> 02:42:03.552
But that's still two, and if the electron lives in a spin-up, spin-down in the top, or a spin-up, spin-down in the bottom...

2961
02:42:05.005 --> 02:42:05.809
There's still a problem.

2962
02:42:05.829 --> 02:42:06.853
Because now you've got four.

2963
02:42:06.994 --> 02:42:08.581
Again, I only want two.

2964
02:42:08.601 --> 02:42:08.922
Yeah.

2965
02:42:08.942 --> 02:42:09.083
Yeah.

2966
02:42:10.121 --> 02:42:10.401
Okay.

2967
02:42:11.061 --> 02:42:13.242
And that's been kind of a problem.

2968
02:42:14.243 --> 02:42:28.749
This is a limiting factor because the position, like this impacts everything else downstream from a qubit quality and qubit control perspective.

2969
02:42:28.769 --> 02:42:29.010
Both.

2970
02:42:29.530 --> 02:42:29.810
Both.

2971
02:42:30.050 --> 02:42:30.850
You're very correct.

2972
02:42:31.431 --> 02:42:31.711
Both.

2973
02:42:31.891 --> 02:42:35.372
Qubit quality in terms of I don't really have a well-defined zero and a one.

2974
02:42:35.633 --> 02:42:38.334
And qubit control because if I try to kick my zero,

2975
02:42:39.437 --> 02:42:45.162
201, how do I know I didn't go into the other zero of the other valley state or some nonsense, right?

2976
02:42:45.562 --> 02:42:53.950
And when I'm reading it out specifically, like, and I'm trying to do this polyspin blockade thing where I, like, shoved, like, what if the stuff goes into the other valley state?

2977
02:42:54.010 --> 02:42:54.130
Right.

2978
02:42:54.150 --> 02:42:54.310
Right.

2979
02:42:55.468 --> 02:42:57.869
This is like kind of an existential – It's fundamental.

2980
02:42:57.949 --> 02:42:58.909
It's a fundamental problem.

2981
02:42:58.929 --> 02:43:05.812
Because if you don't solve this, then you can't get to sustainability in cubic quality or cubic control.

2982
02:43:05.832 --> 02:43:06.292
Yeah, yeah.

2983
02:43:06.512 --> 02:43:08.453
And then scalability is a matter of thing.

2984
02:43:08.573 --> 02:43:10.073
Right, right, right, right, right, right, right.

2985
02:43:10.274 --> 02:43:13.675
Because we still have this – there's a physical – it's about the material.

2986
02:43:13.695 --> 02:43:22.018
So this is a problem that arises out of the actual physical manufacturing of the material, both in like the quality of it and then – anyway.

2987
02:43:22.398 --> 02:43:22.778
Exactly.

2988
02:43:22.798 --> 02:43:23.299
This is a big deal.

2989
02:43:23.319 --> 02:43:25.100
This is a big deal that needs to get solved.

2990
02:43:25.160 --> 02:43:32.364
I can understand why people are like, yeah, yeah, because it seems like just like this magic trick that silicon does that, first of all, they don't even understand.

2991
02:43:32.404 --> 02:43:39.209
So then when someone tells them, oh, it's impossible, I'm going to go do my neutral atoms nonsense in Munich, Germany.

2992
02:43:40.729 --> 02:43:41.050
Sorry.

2993
02:43:41.550 --> 02:43:43.151
So anyways, there's that.

2994
02:43:43.471 --> 02:43:49.695
And then finally, there's also a wiring problem because each of these gates, you know, as I told you, there's a wire that has to go in.

2995
02:43:49.995 --> 02:43:52.737
and control the plus five, minus five, plus five, minus five.

2996
02:43:52.837 --> 02:43:54.879
Each of these have to be independent wires that go in.

2997
02:43:55.219 --> 02:43:59.262
And so you're sort of met with the same wiring problem that you had with superconducting qubits.

2998
02:43:59.282 --> 02:43:59.943
Conducting qubits, yeah.

2999
02:43:59.963 --> 02:44:04.446
Except it's a little bit better because with superconducting qubits, you had coax cables that were like semi-rigid.

3000
02:44:04.746 --> 02:44:07.088
Here, at least, you've got like just wires, right?

3001
02:44:07.428 --> 02:44:08.789
So it's a little bit more tractable.

3002
02:44:09.170 --> 02:44:10.971
Inherently, though, there is still a wiring problem.

3003
02:44:11.031 --> 02:44:11.231
Okay.

3004
02:44:11.832 --> 02:44:12.052
Okay.

3005
02:44:12.428 --> 02:44:15.150
Now let's finally talk about HRL and this particular paper.

3006
02:44:15.270 --> 02:44:15.490
Yes.

3007
02:44:15.590 --> 02:44:17.412
Because that's sort of where we landed.

3008
02:44:17.652 --> 02:44:17.852
Yes.

3009
02:44:17.992 --> 02:44:18.232
Right?

3010
02:44:18.312 --> 02:44:20.654
With why people think spin qubits ain't going to be it.

3011
02:44:20.834 --> 02:44:20.994
Right.

3012
02:44:21.215 --> 02:44:21.475
Okay?

3013
02:44:21.795 --> 02:44:33.504
Now, HRL, for those who don't know, it started its life out as Hughes Research Labs after Howard Hughes, who is the Leonardo DiCaprio character in The Aviator.

3014
02:44:33.584 --> 02:44:33.804
Yes.

3015
02:44:34.004 --> 02:44:35.785
And if you've seen that movie, there's like this…

3016
02:44:36.826 --> 02:44:43.689
There's like this gaggle of engineers and scientists that are trying to make him this crazy airplane.

3017
02:44:44.590 --> 02:44:48.032
And he goes to them and he's like, these rivets are on the airplane.

3018
02:44:48.052 --> 02:44:49.472
They need to be completely flush.

3019
02:44:49.572 --> 02:44:50.693
And they spend their time like...

3020
02:44:52.097 --> 02:45:19.142
sanding down the rivets on the airplane and then he takes it for a ride and he like lands in a cotton field and crazy things like that those engineers and scientists are what became Hughes research labs now at the time of the movie there was no hrl but i feel like that's yeah that's hrl okay it was like howard hughes going and being like make me this and then they do it he got this nice little plot of land right above pepperdine university in malibu and he built that lab um it's

3021
02:45:22.503 --> 02:45:25.224
it invented the laser way back in the day.

3022
02:45:25.364 --> 02:45:29.805
Didn't get the Nobel prize because the Maser won the Nobel prize for microwave amplification.

3023
02:45:30.165 --> 02:45:31.885
The laser was the optical version of that.

3024
02:45:31.925 --> 02:45:33.026
So the Maser had already won.

3025
02:45:33.046 --> 02:45:34.446
I think that's why the laser didn't win.

3026
02:45:35.366 --> 02:45:39.167
Kind of weird because like other places, other laser things have won for a lot less.

3027
02:45:39.707 --> 02:45:44.288
So HRL has been working on encoded spin qubits for a while.

3028
02:45:44.308 --> 02:45:47.729
They've had a lot of papers over the past decades.

3029
02:45:48.109 --> 02:45:50.050
A big one came out in 2023.

3030
02:45:50.250 --> 02:45:51.270
It was submitted, I think, in 2022.

3031
02:45:53.431 --> 02:46:11.348
this one was in 2023 universal logic with encoded spin qubits in silicon here they showed an instance of the first universal logic meaning universal computational logic like you can do anything you want with two qubits but remember two qubits with exchange only

3032
02:46:12.187 --> 02:46:14.110
means six electrons.

3033
02:46:14.210 --> 02:46:16.394
So there were six electrons, yeah.

3034
02:46:16.814 --> 02:46:19.859
And we've got a little video that shows exactly how that works.

3035
02:46:20.200 --> 02:46:21.782
So here you've got your six qubits

3036
02:46:22.683 --> 02:46:27.426
the six sort of potential wells, and the blue are the exchange gates, the barriers in between.

3037
02:46:27.926 --> 02:46:28.166
Okay?

3038
02:46:29.027 --> 02:46:29.967
This is the wiring.

3039
02:46:30.447 --> 02:46:33.029
And here you can see sort of the wiring problem already.

3040
02:46:33.849 --> 02:46:40.573
Even with those six cubits, there's all these wires that need to go in to control the voltages in that little environment.

3041
02:46:40.593 --> 02:46:40.753
Yeah.

3042
02:46:41.053 --> 02:46:41.253
Right?

3043
02:46:41.333 --> 02:46:41.453
Yeah.

3044
02:46:41.473 --> 02:46:41.574
Yeah.

3045
02:46:42.714 --> 02:46:47.217
These are the gates that go through the silicon heterostructure, as you can see.

3046
02:46:47.737 --> 02:46:51.700
And right in that layer there is where the electrons are confined.

3047
02:46:52.200 --> 02:46:54.121
Three at a time for a single qubit.

3048
02:46:54.181 --> 02:46:58.864
It's called a DFS qubit here because it's decoherence-free subspace.

3049
02:46:58.984 --> 02:47:01.746
That's the whole idea of I don't care about magnetic fields.

3050
02:47:02.066 --> 02:47:05.568
So I'm free from decoherence due to magnetic fields.

3051
02:47:05.928 --> 02:47:08.130
And now you can see the voltage pulses come in.

3052
02:47:08.931 --> 02:47:10.758
They mix the electrons together.

3053
02:47:11.260 --> 02:47:13.108
And that is everything that is needed.

3054
02:47:14.735 --> 02:47:16.216
For all logical operations.

3055
02:47:16.336 --> 02:47:25.239
And then what we're seeing with the squiggles, is it kind of similar to the resonance lines we saw in, I guess it would have been the superconducting qubits?

3056
02:47:25.359 --> 02:47:27.020
Oh, these squiggles over here?

3057
02:47:27.040 --> 02:47:27.320
Yeah.

3058
02:47:27.360 --> 02:47:32.221
No, that's a representation of which two electrons are getting mixed at a time.

3059
02:47:32.281 --> 02:47:32.501
Okay.

3060
02:47:32.682 --> 02:47:34.602
So it's basically giving us our zero and one.

3061
02:47:34.642 --> 02:47:35.082
Yeah, yeah.

3062
02:47:35.122 --> 02:47:38.864
It's giving us our, yeah, like the zero and one is the three electrons.

3063
02:47:40.092 --> 02:47:44.995
The three here being in either a singlet or a triplet, the three here being in either a singlet or a triplet plus whatever.

3064
02:47:45.815 --> 02:47:53.220
And the squiggles are telling you like if there are six independent lines, that tells you that you're doing nothing.

3065
02:47:53.680 --> 02:48:00.044
If two of the lines come together, that's telling you that you're removing the barrier in between those two lines.

3066
02:48:00.124 --> 02:48:04.146
And so this is a quantum sort of like a simple gate operation that you're performing.

3067
02:48:04.186 --> 02:48:04.827
I got you.

3068
02:48:04.907 --> 02:48:06.628
It's a two-qubit gate operation.

3069
02:48:06.848 --> 02:48:11.913
I don't actually know what exactly the gate is that is being represented in this video.

3070
02:48:12.353 --> 02:48:18.459
Again, if there are former colleagues in the comments, let me know what exactly this gate is.

3071
02:48:18.939 --> 02:48:20.441
But in any case, that's the idea, right?

3072
02:48:20.481 --> 02:48:21.122
It's the golden gate.

3073
02:48:21.162 --> 02:48:21.602
No, I'm playing that.

3074
02:48:22.765 --> 02:48:28.949
Yeah, so the golden electrodes are what maintain the valleys, right?

3075
02:48:29.090 --> 02:48:33.933
And then the little blue pulses come in to make the electrons mix together.

3076
02:48:34.233 --> 02:48:38.756
And whenever a blue pulse comes in, those two lines sort of come together.

3077
02:48:38.776 --> 02:48:40.938
Basically, our hotel rooms are where the pink is.

3078
02:48:41.038 --> 02:48:44.981
The door in between the hotel rooms, in our analogy from earlier, is when they start coming together.

3079
02:48:45.001 --> 02:48:47.903
That's when the doors open and that's being triggered by the pulses that were coming.

3080
02:48:48.003 --> 02:48:48.383
Exactly.

3081
02:48:48.403 --> 02:48:49.224
Having down the gold.

3082
02:48:49.304 --> 02:48:50.725
And then we were reading out again...

3083
02:48:51.245 --> 02:48:53.266
state based on whether they're not coming together.

3084
02:48:53.366 --> 02:48:59.229
And then these two on the left, that's the single electron transistor on the left here.

3085
02:48:59.309 --> 02:49:01.429
That's the thing that is sensing.

3086
02:49:01.650 --> 02:49:04.851
That's the M1, the Z, M1, Z2.

3087
02:49:05.231 --> 02:49:07.252
Those are the single electron transistors.

3088
02:49:07.412 --> 02:49:09.213
Got it.

3089
02:49:09.233 --> 02:49:10.273
Because they can sense what's happening.

3090
02:49:10.293 --> 02:49:11.054
It's the elevator shaft.

3091
02:49:11.174 --> 02:49:11.594
Exactly.

3092
02:49:11.634 --> 02:49:16.196
And then they can sense, like, when we finally want to read it out, we'll shove the two into one.

3093
02:49:16.616 --> 02:49:18.757
If they get shoved together, then you've got to

3094
02:49:19.481 --> 02:49:43.384
um singlet if they don't get shoved together then you've got a triplet and you can you can figure that out makes sense okay so this is this is the quantum computer right okay like that's made in silicon okay yes right it's printed in silicon yes the gate electrodes are all like printed the same way that you sort of print a chip yep and it works and it works right for two cubic gates it totally works this was in 2022 and this is right around the time that i started my job yep at hrl

3095
02:49:44.154 --> 02:49:47.739
I got involved about a year in into my career at HRL.

3096
02:49:48.120 --> 02:49:49.081
I was having a great time.

3097
02:49:49.882 --> 02:49:51.685
More on what I did specifically later.

3098
02:49:51.765 --> 02:49:52.767
And then came early 2026.

3099
02:49:54.697 --> 02:49:57.278
when HRL lost significant program funding.

3100
02:49:57.358 --> 02:50:09.060
I know I can say this because Thaddeus Ladd, who's one of the corresponding authors on this paper, he went on a podcast with Sebastian Hessinger called the New Quantum Era Podcast.

3101
02:50:09.360 --> 02:50:14.161
If you want to hear it from one of the corresponding authors on this paper, go check out that podcast.

3102
02:50:14.201 --> 02:50:15.322
It's not that long.

3103
02:50:15.342 --> 02:50:20.023
This is going to be a three-hour long podcast, but that one's only 40 minutes.

3104
02:50:20.603 --> 02:50:20.763
Yeah.

3105
02:50:21.483 --> 02:50:23.424
And it was announced to the world in February.

3106
02:50:23.464 --> 02:50:35.207
There's a bunch of headlines from the great journalistic powerhouses of the Malibu Times and the Los Angeles Daily News talking about how HRL had to lay off 376 employees.

3107
02:50:36.488 --> 02:50:40.549
Malibu's HRL Labs cuts that many jobs after losing government work.

3108
02:50:41.089 --> 02:50:44.550
So HRL was kind of in a crisis mode.

3109
02:50:44.867 --> 02:50:51.251
And they transitioned from working on this stuff to now we need to commercialize this.

3110
02:50:51.952 --> 02:50:55.574
We need to bring in some outside work to commercialize this.

3111
02:50:55.614 --> 02:50:56.675
Maybe someone's going to buy us.

3112
02:50:57.055 --> 02:50:58.536
And that's when IBM comes in later.

3113
02:50:58.916 --> 02:51:06.681
I want to make a quick note here about when we talk about funding conversations, there's a difference between basic research and applied research or applied technologies.

3114
02:51:07.242 --> 02:51:10.484
And this is kind of that line that is being straddled here because –

3115
02:51:11.324 --> 02:51:19.408
And correct me if I'm wrong here, to some extent, in its initial conception, it was still – it was going to eventually be applied somehow.

3116
02:51:19.788 --> 02:51:25.511
But the context was let's just do this as a basic research function and figure out how to get to stability here.

3117
02:51:25.851 --> 02:51:35.295
However, the government is cutting basic – generally, it's cutting basic research in favor for applied research.

3118
02:51:35.475 --> 02:51:35.675
Yeah.

3119
02:51:35.695 --> 02:51:38.977
Which basically means where can we go invest our money and make billions of dollars?

3120
02:51:38.997 --> 02:51:39.297
Yeah.

3121
02:51:40.257 --> 02:51:41.518
How can we productize stuff?

3122
02:51:41.638 --> 02:51:44.618
How can we create this golden age of American technology?

3123
02:51:44.998 --> 02:51:47.359
That is kind of the shtick right now.

3124
02:51:47.499 --> 02:52:00.222
And as such, IBM in the Chips Act was given a prop around this idea of we need to create re-onshore chip manufacturing.

3125
02:52:01.142 --> 02:52:02.062
Intel too, I think.

3126
02:52:02.102 --> 02:52:06.264
Intel and IBM are two great American chip makers, right?

3127
02:52:06.644 --> 02:52:08.324
And how do we compete and both?

3128
02:52:09.050 --> 02:52:26.455
This is the background context in which this is happening, where there's a huge federal policy funding shift to putting money where it is perceived that it can boost stock prices, basically.

3129
02:52:26.635 --> 02:52:26.895
Yeah.

3130
02:52:27.215 --> 02:52:29.236
I mean, I don't know much about that.

3131
02:52:29.696 --> 02:52:31.036
But that's the context.

3132
02:52:31.256 --> 02:52:32.257
That's the context, yeah.

3133
02:52:33.637 --> 02:52:46.248
And it's not – it's very explicit in the documentation coming out of the executive offices, the president of the White House in terms of how they've defined – you have this project with the Department of Energy where they're doing the same idea.

3134
02:52:46.268 --> 02:52:52.213
The idea is we want to decompress the time from research to applications.

3135
02:52:52.725 --> 02:52:54.506
That's how it's framed, right?

3136
02:52:55.106 --> 02:52:58.487
And application means monetization, ultimately.

3137
02:52:59.047 --> 02:53:02.288
And how do we make this something that actually can generate GDP value?

3138
02:53:02.729 --> 02:53:12.232
Because they want to mimic what's been done with AI in terms of boosting growth, GDP growth in the U.S., in every other industry much more quickly.

3139
02:53:12.532 --> 02:53:12.732
Yeah.

3140
02:53:12.992 --> 02:53:14.413
So that's the context.

3141
02:53:14.773 --> 02:53:18.374
Again, a separate issue and a separate topic.

3142
02:53:19.054 --> 02:53:25.356
And my viewpoint on this, not that of Krishna's for those who are listening, who are still listening, who are his teammates.

3143
02:53:25.736 --> 02:53:26.657
But again, it's weird.

3144
02:53:26.677 --> 02:53:33.419
People get weirdly emotional about this subject in ways that it doesn't make sense to me because it's just – it's literally what they're saying.

3145
02:53:33.559 --> 02:53:33.779
Yeah.

3146
02:53:34.859 --> 02:53:39.221
I mean, the White House is very explicit in its executive orders and its website, whitehouse.gov.

3147
02:53:39.761 --> 02:53:40.682
You can check it out, right?

3148
02:53:41.082 --> 02:53:45.044
So in any case, HRL loses significant program funding.

3149
02:53:45.384 --> 02:53:52.427
And so this is when HRL decides to sort of come out with this work.

3150
02:53:52.787 --> 02:53:58.670
And during that reduction force, I had to move on to other places.

3151
02:53:59.250 --> 02:53:59.570
So...

3152
02:54:00.620 --> 02:54:03.801
APS March meeting is also coming up right after this event.

3153
02:54:04.261 --> 02:54:06.863
And so at APS March meeting, we're all giving our talks.

3154
02:54:06.903 --> 02:54:12.925
And we had already sort of applied to give the talks, but now there's this kind of urgency to give these talks, right?

3155
02:54:14.165 --> 02:54:17.187
And we're not presenting the stuff that's in this paper.

3156
02:54:17.247 --> 02:54:18.547
We all have like our own talks.

3157
02:54:18.587 --> 02:54:25.430
And I had the last talk before the big talk of Thaddeus Ladd, who's one of the corresponding authors on this paper, right?

3158
02:54:25.790 --> 02:54:28.011
And we're presenting stuff that's adjacent to it.

3159
02:54:30.732 --> 02:54:33.614
At March meeting that Thaddeus' talk is going to be this big talk.

3160
02:54:34.194 --> 02:54:34.455
Okay.

3161
02:54:34.915 --> 02:54:37.857
It's going to, he's going to present some like really cool results.

3162
02:54:39.038 --> 02:54:42.460
I had the last HRL talk before Thaddeus'.

3163
02:54:42.960 --> 02:54:47.944
And in my last slide, I snuck in a photo of some of the stuff that's shown here.

3164
02:54:48.404 --> 02:54:54.688
And it was really funny, actually, just to give you guys kind of an insider of like, you know, how conferences work and things like that.

3165
02:54:55.808 --> 02:54:58.154
This was a talk in the automation section.

3166
02:54:58.736 --> 02:55:00.500
And spin qubits is quite a big field.

3167
02:55:00.521 --> 02:55:02.185
So it was quite a crowded event.

3168
02:55:03.672 --> 02:55:25.223
people came and in the last slide I showed like a little sneak peek of this stuff and I dropped it like it was like you know in a Nickelodeon shows that they'd have those celebrity cameos and like they'd stop and then the audience would like go crazy it was like when that happened like everybody took out their phones and started taking photographs um in the audience because this was all new stuff and I said you know

3169
02:55:26.283 --> 02:55:26.964
More on this.

3170
02:55:27.424 --> 02:55:28.305
Go to Thaddeus' talk.

3171
02:55:28.345 --> 02:55:29.226
It's going to be a banger.

3172
02:55:29.666 --> 02:55:31.688
And a lot of people showed up.

3173
02:55:31.748 --> 02:55:44.178
This was in a big conference room, one of these big spin-cubit exposés where you had HRL giving a talk, Intel giving a talk, Dirac, which is where I'm currently at, giving a talk.

3174
02:55:45.358 --> 02:55:49.442
And Thaddeus goes up on stage and he drops this image.

3175
02:55:49.602 --> 02:55:51.844
This is one of his first slides that he drops.

3176
02:55:52.764 --> 02:55:53.385
This is...

3177
02:55:55.201 --> 02:55:56.102
The quantum silicon.

3178
02:55:57.182 --> 02:55:57.442
Okay.

3179
02:55:58.303 --> 02:55:59.783
It's got 18 qubits now.

3180
02:56:00.124 --> 02:56:00.464
Okay.

3181
02:56:01.284 --> 02:56:05.426
So 18 times 3, there's 54 electrons that are moving around in this thing.

3182
02:56:06.147 --> 02:56:11.390
And this thing has enough wiring that is comparable to Google's Willow.

3183
02:56:11.690 --> 02:56:12.830
That's crazy.

3184
02:56:14.271 --> 02:56:15.132
That's actually crazy.

3185
02:56:15.152 --> 02:56:15.252
Yeah.

3186
02:56:15.272 --> 02:56:15.492
Yeah.

3187
02:56:16.950 --> 02:56:19.113
We don't need microwave coax.

3188
02:56:19.433 --> 02:56:20.475
That's so crazy.

3189
02:56:20.515 --> 02:56:20.775
Right?

3190
02:56:21.276 --> 02:56:21.436
Right.

3191
02:56:21.456 --> 02:56:23.058
This just looks like a PC.

3192
02:56:23.479 --> 02:56:23.719
Yeah.

3193
02:56:24.520 --> 02:56:24.861
Yeah.

3194
02:56:25.041 --> 02:56:25.322
Right?

3195
02:56:25.622 --> 02:56:28.566
I mean, it's a lot of metal instead of like plastic.

3196
02:56:28.746 --> 02:56:28.947
Sure.

3197
02:56:29.187 --> 02:56:30.509
That's like in the gaming PCs.

3198
02:56:30.569 --> 02:56:32.752
But it kind of just looked like there's a printed circuit board.

3199
02:56:32.772 --> 02:56:33.433
There's like these like...

3200
02:56:34.113 --> 02:56:42.419
The, you know, ribbon cables that are coming in, flex cables that like connect your GPU to your monitor and things like that.

3201
02:56:43.200 --> 02:56:44.741
It looks like a custom PC.

3202
02:56:44.761 --> 02:56:46.262
But it just looks kind of boring.

3203
02:56:46.402 --> 02:56:46.582
Yeah.

3204
02:56:46.943 --> 02:56:48.303
And that's kind of the point.

3205
02:56:48.344 --> 02:56:48.564
Right.

3206
02:56:49.164 --> 02:56:52.306
Boring is good because boring is scalable.

3207
02:56:52.987 --> 02:56:53.247
Okay.

3208
02:56:54.168 --> 02:56:57.250
Now, the next photo we have, it's labeled.

3209
02:56:57.270 --> 02:56:57.410
Okay.

3210
02:56:58.338 --> 02:56:59.199
Although I don't know if you can see.

3211
02:56:59.219 --> 02:57:03.502
So on the bottom, you've got the chip itself, right?

3212
02:57:03.862 --> 02:57:05.423
Before you had just 3 and 3.

3213
02:57:06.424 --> 02:57:13.330
Now you've got 54 down there and a bunch of single electron transistors on the bottom.

3214
02:57:13.790 --> 02:57:15.972
So that's your qubit chip.

3215
02:57:16.312 --> 02:57:17.493
They call it a daughter board?

3216
02:57:17.875 --> 02:57:19.675
Yeah, that's the daughterboard at the very bottom.

3217
02:57:19.695 --> 02:57:20.056
At the bottom.

3218
02:57:20.076 --> 02:57:23.256
Okay, that is being held up like this from the two sides and then the bottom.

3219
02:57:23.516 --> 02:57:23.656
Okay.

3220
02:57:23.696 --> 02:57:26.017
That thing is at the millikelvin temperature.

3221
02:57:26.317 --> 02:57:26.517
Right.

3222
02:57:26.697 --> 02:57:27.077
Okay.

3223
02:57:27.137 --> 02:57:27.417
Yeah.

3224
02:57:27.537 --> 02:57:30.318
And only that needs to be maintained at that temperature.

3225
02:57:30.338 --> 02:57:31.198
At the millikelvin temperature.

3226
02:57:31.238 --> 02:57:31.858
That's kind of nice.

3227
02:57:31.898 --> 02:57:32.679
That's kind of nice.

3228
02:57:32.699 --> 02:57:33.179
That is key.

3229
02:57:33.619 --> 02:57:34.619
That's kind of nice.

3230
02:57:35.119 --> 02:57:43.521
Okay, but the green part that you're seeing behind it that's coming down there, that thing is actually not connected to the side and the bottom.

3231
02:57:43.741 --> 02:57:44.001
Okay.

3232
02:57:44.302 --> 02:57:44.562
Okay?

3233
02:57:44.962 --> 02:57:45.662
Except...

3234
02:57:46.282 --> 02:57:50.103
For a little tiny cable at the back there.

3235
02:57:50.523 --> 02:57:56.864
And I don't know if you could see this, but actually let's remove the thing so I can show you.

3236
02:57:57.004 --> 02:57:57.204
Yes.

3237
02:57:57.424 --> 02:58:00.865
So here we've got the daughterboard on the bottom.

3238
02:58:00.965 --> 02:58:01.165
Yeah.

3239
02:58:01.525 --> 02:58:03.165
You see that square that's highlighted?

3240
02:58:03.245 --> 02:58:03.726
Yep.

3241
02:58:03.746 --> 02:58:04.466
That's the chip.

3242
02:58:04.766 --> 02:58:08.727
That's the quantum chip with the 54 electrons, 18 cubits.

3243
02:58:08.827 --> 02:58:09.067
Yep.

3244
02:58:09.847 --> 02:58:15.268
This is the 4 Kelvin stage that has something called a cryo controller, which we're going to get to.

3245
02:58:15.908 --> 02:58:19.511
But the key thing is this bottom part is at tens of millikelvin.

3246
02:58:20.171 --> 02:58:22.033
This top part here is at four kelvin.

3247
02:58:22.453 --> 02:58:27.057
And the only connection between these two is this highlighted part here.

3248
02:58:27.377 --> 02:58:28.938
A little corner pipe.

3249
02:58:28.978 --> 02:58:29.338
Yes.

3250
02:58:30.119 --> 02:58:33.962
All of the electronics, if this electronics wants to talk to the daughter board,

3251
02:58:34.386 --> 02:58:37.188
It only has to go through the superconducting ribbon cable.

3252
02:58:37.248 --> 02:58:39.010
That's actually really nice.

3253
02:58:39.030 --> 02:58:43.854
That's really nice because there's no thermal loading into the daughterboard.

3254
02:58:43.894 --> 02:58:44.774
That's the key.

3255
02:58:45.014 --> 02:58:47.496
These are separated inside a vacuum chamber.

3256
02:58:47.737 --> 02:58:54.282
And the dilution refrigerator, the helium that's pumping, is pumping on this bottom part that is going to create that tens of millikelvin.

3257
02:58:54.731 --> 02:58:55.932
That's actually really clever.

3258
02:58:56.192 --> 02:58:56.572
Yeah.

3259
02:58:56.592 --> 02:59:02.615
You've basically created like a Lincoln Tunnel of where everything needs to go through to get to New York City.

3260
02:59:03.055 --> 02:59:08.678
But the thing is, it's like a wide Lincoln Tunnel with a lot of lanes.

3261
02:59:08.698 --> 02:59:09.258
Yeah.

3262
02:59:09.698 --> 02:59:12.199
And you don't have congestion problems or anything.

3263
02:59:12.339 --> 02:59:12.439
Yeah.

3264
02:59:12.459 --> 02:59:14.560
It's just like if Lincoln Tunnel was actually efficient.

3265
02:59:14.640 --> 02:59:16.161
If it was actually efficient, right?

3266
02:59:16.541 --> 02:59:19.163
And if you go back to that photo 73.

3267
02:59:19.203 --> 02:59:19.283
Yep.

3268
02:59:21.393 --> 02:59:21.573
Right?

3269
02:59:21.633 --> 02:59:23.594
So on the bottom, that's the millikelvin stage.

3270
02:59:23.794 --> 02:59:25.115
That's got your qubits.

3271
02:59:25.815 --> 02:59:28.757
The cryocontroller is another big part of this setup.

3272
02:59:29.197 --> 02:59:30.398
And that's at the top there.

3273
02:59:30.498 --> 02:59:32.059
We're going to get into what that actually does.

3274
02:59:32.419 --> 02:59:36.401
And the way that cryocontroller controls the qubits at the bottom is through...

3275
02:59:37.001 --> 02:59:54.793
the ribbon cable which in this in this kind of diagram we can kind of see in that smaller golden box below in the white yeah yeah it's going like behind it you can't see it because it's behind it's like outlined with like a little it's the same thing as here like it literally it's like yeah no that that makes it

3276
02:59:55.313 --> 03:00:13.520
that's okay so i can already i can already see now where this is going because of what we've previously laid the table for why that architectural or structural design choice is going to be meaningful in terms of our criterion and now let's let's go to the um let's go let's take a look at the actual qubits okay

3277
03:00:14.161 --> 03:00:20.352
So this is just a bigger version of that six electrons that we had seen earlier.

3278
03:00:20.412 --> 03:00:21.434
Now we've got 54.

3279
03:00:21.895 --> 03:00:23.578
Again, there's wiring.

3280
03:00:24.379 --> 03:00:25.922
But all of this wiring is...

3281
03:00:26.945 --> 03:00:56.195
silicon yeah you can print it like a chip we know how to do this with the lithography stuff that asml does yes as an example as an example right this is not done with the same like euv lithography but there's no reason why it wouldn't be able to right sure for sure um and so here you've got 54 um electrons that are being controlled there's like two there's like two wires in each because there's a barrier and then there's a there's a spot where it sits there is the 2d confinement of the electrons quite nice right right

3282
03:00:57.334 --> 03:01:00.796
Each of the electrons are sitting under these plunger gates, we call them.

3283
03:01:00.896 --> 03:01:03.497
Those are the purples.

3284
03:01:03.557 --> 03:01:04.517
That's a single qubit.

3285
03:01:04.597 --> 03:01:05.718
There's three.

3286
03:01:05.738 --> 03:01:08.419
And control pulses come in in the barrier gates.

3287
03:01:09.123 --> 03:01:27.871
to give you oh this is nice dude this is nice yeah this is nice we we already know how to do all of the engineering of the substrate yeah the what was really missing was the like what you needed it to look like and do architecturally and then obviously the larger system around it but yeah

3288
03:01:29.458 --> 03:01:32.981
But this, you can see that maybe this can probably scale.

3289
03:01:33.561 --> 03:01:56.741
I can, one, already from just, again, the, how can we control and read makes sense based on what we've talked about this, like with the potential wells, why we're doing the singlet and triplet and like the lack of global interference, but there's still local interference, which can be handled with all the things we've talked about.

3290
03:01:56.761 --> 03:01:57.521
Yeah.

3291
03:01:58.446 --> 03:02:14.217
But I think the ability to do this in silicon is like a huge, again, not knowing really much otherwise, seems to me to be a huge enabling layer for all of the reasons we've kind of talked about.

3292
03:02:14.477 --> 03:02:14.697
Yeah.

3293
03:02:15.298 --> 03:02:22.923
And the fact that the in silica like works, like still has its own unique benefits.

3294
03:02:23.846 --> 03:02:27.167
For the quality and control aspects that are independent of the scalability.

3295
03:02:27.367 --> 03:02:28.307
It's not just a scalability solution.

3296
03:02:28.327 --> 03:02:30.108
There's the chip, and then you zoom out.

3297
03:02:30.448 --> 03:02:31.848
That goes inside the daughterboard.

3298
03:02:33.109 --> 03:02:34.049
Looks like a computer.

3299
03:02:34.289 --> 03:02:34.509
Yeah.

3300
03:02:35.309 --> 03:02:36.890
And you can handle the cooling separately.

3301
03:02:37.830 --> 03:02:42.251
And there's going to be aspects of the cooling that I want to talk about that are really cool.

3302
03:02:42.271 --> 03:02:44.312
The Cryo controller has a lot to do with that.

3303
03:02:44.392 --> 03:02:46.712
But all of this sits inside of a dilution refrigerator.

3304
03:02:47.272 --> 03:02:48.573
And there's plenty of space.

3305
03:02:49.375 --> 03:02:50.357
For more qubits.

3306
03:02:50.577 --> 03:02:50.818
Yeah.

3307
03:02:51.499 --> 03:02:53.082
Each of these things is tens of nanometers.

3308
03:02:53.102 --> 03:02:53.322
Yeah.

3309
03:02:53.603 --> 03:02:54.925
Unlike superconducting qubits.

3310
03:02:54.965 --> 03:02:55.186
Right.

3311
03:02:55.226 --> 03:02:56.508
That are millimeters.

3312
03:02:57.470 --> 03:02:57.690
Right?

3313
03:02:57.770 --> 03:02:57.931
And so.

3314
03:02:57.971 --> 03:02:59.533
There's plenty of space on a wafer.

3315
03:03:00.710 --> 03:03:02.090
For more stuff.

3316
03:03:02.130 --> 03:03:04.691
We can fit a lot into our data center than your data center.

3317
03:03:04.771 --> 03:03:05.011
Yeah.

3318
03:03:05.931 --> 03:03:09.032
And all it requires is like a single dilution refrigerator, or maybe two.

3319
03:03:09.052 --> 03:03:14.073
You don't need a whole data center worth of... A data center can now have multiple quantum computers, not a single one.

3320
03:03:14.353 --> 03:03:15.874
Which is, again, the scalability.

3321
03:03:15.914 --> 03:03:17.254
But we'll get back to that.

3322
03:03:17.294 --> 03:03:17.434
Yeah.

3323
03:03:17.634 --> 03:03:19.234
I mean, there's a lot more to talk about, right?

3324
03:03:19.254 --> 03:03:19.394
Right.

3325
03:03:19.754 --> 03:03:20.395
Unfortunately.

3326
03:03:21.255 --> 03:03:22.535
No, we're going to get it.

3327
03:03:22.555 --> 03:03:23.255
No, we're doing well.

3328
03:03:24.256 --> 03:03:25.856
And I mean, I love talking about this stuff.

3329
03:03:26.176 --> 03:03:26.836
So, okay.

3330
03:03:27.336 --> 03:03:30.157
How do you keep that qubit chip isolated thermally?

3331
03:03:30.937 --> 03:03:31.117
Right.

3332
03:03:31.298 --> 03:03:31.498
Right.

3333
03:03:31.738 --> 03:03:37.102
And I kind of alluded to this with the ribbon cable and so on and so forth, but let's actually get into it.

3334
03:03:37.362 --> 03:03:47.629
So over here, we've got, as I said, on the bottom is our qubit chip with the 54 quantum dots.

3335
03:03:48.590 --> 03:03:51.973
That's connected via ribbon cable to this cryo controller.

3336
03:03:51.993 --> 03:03:52.113
Right.

3337
03:03:52.892 --> 03:03:54.013
Here's what's actually happening.

3338
03:03:54.374 --> 03:04:00.420
The cryocontroller from room temperature, room temperature is outside of the dilution refrigerator, right?

3339
03:04:00.460 --> 03:04:04.645
I have a computer where I'm talking to all of the electronics that's going all the way down into this stuff.

3340
03:04:05.285 --> 03:04:12.053
Now, I don't want my room temperature wires to go all the way down to middle Kelvin stage.

3341
03:04:12.747 --> 03:04:12.987
Right.

3342
03:04:13.227 --> 03:04:14.348
That would be really bad.

3343
03:04:15.148 --> 03:04:21.350
Because, again, on one end is room temperature 300 Kelvin, and on the other end is something colder than outer space.

3344
03:04:21.910 --> 03:04:25.151
It's going to be really hard to maintain that thing at colder than outer space.

3345
03:04:25.892 --> 03:04:26.552
So instead...

3346
03:04:27.388 --> 03:04:41.094
You've got this intermediary called the cryo controller assembly where you feed the cryo controller all of these communications, the digital communications, the instructions on what to put the gate.

3347
03:04:41.334 --> 03:04:42.074
Yeah.

3348
03:04:42.454 --> 03:04:44.015
Biases to like, what are the algorithms?

3349
03:04:44.035 --> 03:04:45.476
What are the circuits that I want to implement?

3350
03:04:45.796 --> 03:04:47.396
And furthermore, you don't even have to.

3351
03:04:47.736 --> 03:04:50.678
Furthermore, you don't even have to give it.

3352
03:04:51.538 --> 03:05:10.476
instructions on exactly what the circuit needs to be the cryo controller itself is a chip that has memory and processing yeah so you can give it a instruction on implement this it's got some like memory and processing to be able to know what signals signals to then send through the ribbon cable to our daughter board

3353
03:05:11.222 --> 03:05:16.627
It acts like an air traffic controller to some extent, which has people in it.

3354
03:05:17.067 --> 03:05:20.791
It's not just like routing without intuiting it on its own.

3355
03:05:20.811 --> 03:05:23.994
It has the ability to route, but also be like, ah, that doesn't make sense.

3356
03:05:24.254 --> 03:05:25.355
You can compute.

3357
03:05:25.395 --> 03:05:27.797
There's some headlines that say that it's autonomously controlled.

3358
03:05:27.817 --> 03:05:29.859
This is kind of what they mean by that.

3359
03:05:29.919 --> 03:05:35.284
It's like the cryo controller is given some instructions, but then it's making its own decisions based on the context.

3360
03:05:35.304 --> 03:05:35.764
Yeah.

3361
03:05:36.025 --> 03:05:36.265
Yeah.

3362
03:05:37.225 --> 03:05:38.025
Okay.

3363
03:05:38.466 --> 03:05:39.066
I like that.

3364
03:05:39.086 --> 03:05:45.768
And because the cryo controller is this middleman, you can isolate the room temperature electronics to go to that.

3365
03:05:45.808 --> 03:05:52.650
And then this thing, when it feeds it through the ribbon cable that is superconducting, the amount of thermal leakage is out of minimum.

3366
03:05:52.830 --> 03:05:53.670
Yeah, that makes sense.

3367
03:05:53.970 --> 03:06:00.152
So we're basically splitting out the – we're splitting the journey that the instruction goes to get to its destination –

3368
03:06:00.812 --> 03:06:04.437
We're decoupling the thermal impact from the delivery of the information.

3369
03:06:04.517 --> 03:06:04.938
Exactly.

3370
03:06:05.318 --> 03:06:15.031
One of the reasons why this is important is if we go back to our discussion about superconducting qubits, all of those microwave lines had to go all the way down to the chip.

3371
03:06:15.072 --> 03:06:15.292
Yep.

3372
03:06:16.428 --> 03:06:17.428
There wasn't a middleman.

3373
03:06:18.209 --> 03:06:20.009
It had to go all the way down to the chip.

3374
03:06:20.069 --> 03:06:25.311
And if it goes all the way down to the chip, you're heating up the most delicate part, the part that is the coldest.

3375
03:06:25.892 --> 03:06:29.753
You don't have a lot of power to cool the part that's the coldest.

3376
03:06:30.113 --> 03:06:36.236
It's much easier to cool something that's 4 Kelvin than it is to cool something that's at tens of millikelvin.

3377
03:06:37.396 --> 03:06:38.557
I've got too many wires, man.

3378
03:06:38.597 --> 03:06:39.557
I don't know what to tell you.

3379
03:06:39.777 --> 03:06:41.738
So even though there is a wiring problem...

3380
03:06:42.803 --> 03:06:43.463
It's kind of okay.

3381
03:06:43.904 --> 03:06:44.064
Right.

3382
03:06:44.084 --> 03:06:44.944
At least for this many.

3383
03:06:45.404 --> 03:06:46.125
Right?

3384
03:06:46.145 --> 03:06:50.907
There's arguments to be made about, okay, like, if we get to millions of qubits, the ribbon cable isn't really going to work.

3385
03:06:51.187 --> 03:06:52.348
And we can get into that later.

3386
03:06:52.468 --> 03:06:52.748
Okay.

3387
03:06:52.808 --> 03:06:52.988
Right?

3388
03:06:53.188 --> 03:06:54.969
So it's an MVP for a reason.

3389
03:06:55.369 --> 03:06:55.869
Okay.

3390
03:06:56.129 --> 03:06:57.550
I see paths, but I understand.

3391
03:06:57.650 --> 03:06:58.691
Yeah.

3392
03:06:58.911 --> 03:06:59.211
So...

3393
03:07:00.194 --> 03:07:05.637
Now, that's all fine, but it's not going to amount to anything if you don't get all of the problems that we talked about down.

3394
03:07:06.177 --> 03:07:06.457
Yeah.

3395
03:07:07.038 --> 03:07:07.798
The valleys.

3396
03:07:07.838 --> 03:07:08.438
The valleys.

3397
03:07:08.458 --> 03:07:09.259
The charge noise.

3398
03:07:09.339 --> 03:07:09.579
Yeah.

3399
03:07:10.059 --> 03:07:11.020
The magnetic noise.

3400
03:07:11.100 --> 03:07:11.260
Yeah.

3401
03:07:11.560 --> 03:07:12.160
All of that stuff.

3402
03:07:12.180 --> 03:07:15.202
I mean, you're scaling, but if your qubits are not good.

3403
03:07:15.462 --> 03:07:15.662
Yeah.

3404
03:07:16.022 --> 03:07:20.544
If the qubits are trash, if the gates are trash, if there's so much noise, you're not going to get anywhere.

3405
03:07:20.665 --> 03:07:21.685
Yeah, you can't actually do it.

3406
03:07:21.725 --> 03:07:22.225
Okay.

3407
03:07:22.485 --> 03:07:22.766
So...

3408
03:07:23.666 --> 03:07:25.010
The fidelity has to go up.

3409
03:07:25.130 --> 03:07:29.762
The gates, like, when I say flip this thing, it better be flipping this thing 99.9% of the time.

3410
03:07:29.842 --> 03:07:29.962
Okay?

3411
03:07:29.982 --> 03:07:30.122
Okay.

3412
03:07:32.935 --> 03:07:38.636
Now, if a gate has a fidelity of 99.9%, what that really means is the error rate is 0.1%, right?

3413
03:07:38.696 --> 03:07:39.576
It's just one minus that.

3414
03:07:39.616 --> 03:07:44.197
So one in 1,000 operations are going to result in the wrong state.

3415
03:07:44.737 --> 03:07:48.578
And because quantum algorithms string together a bunch of gates, it compounds.

3416
03:07:49.358 --> 03:07:52.299
And so you really need that fidelity to be really, really high.

3417
03:07:52.499 --> 03:07:52.919
That makes sense.

3418
03:07:52.939 --> 03:07:53.099
Okay?

3419
03:07:53.819 --> 03:07:58.880
Now, this is kind of an interesting little part of...

3420
03:07:59.692 --> 03:08:03.134
this current paper, the fidelity has gone down, gone up by a lot.

3421
03:08:03.194 --> 03:08:12.738
The error rate has gone from that previous 2022, 2023 performance, 3.7% error down to nice 0.09%.

3422
03:08:12.759 --> 03:08:16.100
So just under that 0.1%, right?

3423
03:08:16.140 --> 03:08:18.181
So the performance has really, really gone up.

3424
03:08:18.721 --> 03:08:25.345
And this makes it possible to now really start doing error correction algorithms and things like that, because now I can reliably...

3425
03:08:26.257 --> 03:08:26.937
do gates.

3426
03:08:27.137 --> 03:08:27.338
Yes.

3427
03:08:27.798 --> 03:08:27.998
Yes.

3428
03:08:28.258 --> 03:08:28.358
Okay.

3429
03:08:28.398 --> 03:08:32.100
And also your pace of improvement if you were to extrapolate moving forward.

3430
03:08:33.300 --> 03:08:36.502
We've not necessarily reached the ceiling yet on that performance improvement.

3431
03:08:36.642 --> 03:08:39.243
Actually, it's kind of interesting that you bring that point up.

3432
03:08:39.363 --> 03:08:39.623
Okay.

3433
03:08:39.643 --> 03:08:40.924
So how did they reduce this error?

3434
03:08:41.064 --> 03:08:41.304
Okay.

3435
03:08:41.344 --> 03:08:41.524
Right?

3436
03:08:41.564 --> 03:08:43.165
What is the ceiling, for example?

3437
03:08:43.245 --> 03:08:43.465
Yes.

3438
03:08:43.725 --> 03:08:45.567
Well, there could be two sources to error.

3439
03:08:45.827 --> 03:08:48.289
There could be an intrinsic and an extrinsic source.

3440
03:08:48.770 --> 03:08:50.732
Intrinsic means it's the stuff that we've talked about.

3441
03:08:50.772 --> 03:08:51.733
It's the charge noise.

3442
03:08:52.373 --> 03:08:53.494
It's the magnetic noise.

3443
03:08:54.035 --> 03:08:55.236
It's this valley nonsense.

3444
03:08:55.256 --> 03:08:57.978
This is stuff that is intrinsic to the physics.

3445
03:08:58.179 --> 03:09:01.902
Extrinsic noise is stuff from the engineering, right?

3446
03:09:02.162 --> 03:09:05.305
This is stuff like, how good are my control pulses?

3447
03:09:05.365 --> 03:09:06.486
Are they squares?

3448
03:09:06.807 --> 03:09:08.048
Are they calibrated correctly?

3449
03:09:09.005 --> 03:09:16.252
How good is it to go from room temperature down to there and then from the cryocontroller through the ribbon cable down to this thing?

3450
03:09:16.613 --> 03:09:19.876
Am I losing electricity and stuff as I move through there?

3451
03:09:19.896 --> 03:09:21.378
So that's the extrinsic part.

3452
03:09:21.878 --> 03:09:22.118
Okay?

3453
03:09:22.519 --> 03:09:22.719
Yes.

3454
03:09:23.660 --> 03:09:24.281
Here's the kicker.

3455
03:09:24.461 --> 03:09:26.003
This is a quote from the paper.

3456
03:09:26.723 --> 03:09:29.246
It says, Air is resulting from the mean values of,

3457
03:09:29.710 --> 03:09:30.970
and OSC and T2 star.

3458
03:09:30.990 --> 03:09:36.832
These are two different measurements that you can do to qualify how good your qubit chip is.

3459
03:09:37.752 --> 03:09:45.095
And you can use those measurements to then qualify how much of the error is because of extrinsic sources and intrinsic sources.

3460
03:09:45.655 --> 03:09:54.638
It shows that collectively, those things only contribute to 0.02% of the absolute CNOT error, absolute error in these gates.

3461
03:09:55.098 --> 03:09:55.378
So...

3462
03:09:56.605 --> 03:10:01.847
The intrinsic part of things only contributes to 0.02% of the error.

3463
03:10:03.008 --> 03:10:09.031
This is a subtle way of them saying the physics problems have been solved.

3464
03:10:09.251 --> 03:10:09.451
Yeah.

3465
03:10:09.771 --> 03:10:10.351
Kind of.

3466
03:10:10.532 --> 03:10:10.932
Yeah.

3467
03:10:11.072 --> 03:10:11.792
Okay?

3468
03:10:11.912 --> 03:10:13.493
And then when you go into the...

3469
03:10:15.455 --> 03:10:18.236
Into the methods where they talk about the qubit chip, right?

3470
03:10:18.256 --> 03:10:23.579
Because anyone who's in spin qubits is going to look at this or anyone outside who's like, how did they do that?

3471
03:10:24.079 --> 03:10:27.360
The last sentence just says the SIGI, the silicon germanium heterostructure.

3472
03:10:27.820 --> 03:10:30.522
It was enriched with 28 silicon and depleted with 73 germanium.

3473
03:10:31.955 --> 03:10:34.256
It was engineered to increase valley-splitting energy.

3474
03:10:34.476 --> 03:10:34.836
That's it.

3475
03:10:35.797 --> 03:10:37.457
Okay?

3476
03:10:37.477 --> 03:10:40.218
That's kind of like Lincoln in Lincoln movie.

3477
03:10:40.258 --> 03:10:45.921
He was like, to my knowledge, there's no Confederate negotiators in Washington, D.C.

3478
03:10:46.521 --> 03:10:46.701
Right?

3479
03:10:46.761 --> 03:10:51.763
And then the Confederate sympathizer in Congress was like, that doesn't mean anything.

3480
03:10:52.724 --> 03:10:53.944
That's a lawyer's dodge.

3481
03:10:54.064 --> 03:10:56.205
It's kind of what this feels like.

3482
03:10:56.285 --> 03:10:56.585
Okay.

3483
03:10:56.645 --> 03:10:57.826
Doesn't really mean anything.

3484
03:10:58.607 --> 03:10:58.807
Right.

3485
03:10:58.987 --> 03:10:59.188
Right.

3486
03:10:59.348 --> 03:11:04.072
Here's to here's to underscore that point about about how they're trying to dodge this.

3487
03:11:05.013 --> 03:11:07.315
You know, as you can see, I'm no longer employed at HRL.

3488
03:11:07.355 --> 03:11:09.918
So this is just stuff that is public.

3489
03:11:09.978 --> 03:11:10.158
Right.

3490
03:11:10.719 --> 03:11:12.901
I just read off stuff that's in the paper.

3491
03:11:12.961 --> 03:11:13.561
It's in the paper.

3492
03:11:13.601 --> 03:11:14.242
It's in the paper.

3493
03:11:14.262 --> 03:11:14.582
That's all.

3494
03:11:14.602 --> 03:11:16.104
I just I just read it off.

3495
03:11:16.244 --> 03:11:22.249
In 2021, they showed Valley splitting splitting results in this paper.

3496
03:11:23.352 --> 03:11:33.702
On the left-hand side, on the red, the red shows the distribution of valley-splitting energies that go anywhere from 300 microelectron volts all the way down to, like, 10 to 30.

3497
03:11:34.363 --> 03:11:34.623
Okay?

3498
03:11:35.204 --> 03:11:39.228
Now, crucially, valley-splitting is a difference between energies, so it's always going to be positive.

3499
03:11:39.608 --> 03:11:42.331
What this should remind you of is a Gaussian that's centered at zero.

3500
03:11:43.031 --> 03:11:43.332
Okay?

3501
03:11:43.372 --> 03:11:44.873
That they've just, like, made positive.

3502
03:11:45.314 --> 03:11:45.494
Right?

3503
03:11:45.794 --> 03:11:46.074
So...

3504
03:11:46.980 --> 03:11:51.021
What this is saying is sometimes we get really good energy splitting where it's really high.

3505
03:11:51.362 --> 03:11:53.542
And so my electrons can be localized in one state.

3506
03:11:53.602 --> 03:11:54.643
Sometimes it's really bad.

3507
03:11:54.683 --> 03:11:55.703
Sometimes maybe good.

3508
03:11:56.023 --> 03:11:58.084
Sometimes maybe.

3509
03:11:58.704 --> 03:12:05.466
Gennaro Gattuso was, I think, the gaffer at Lazio now where the transfer when this is funny.

3510
03:12:05.506 --> 03:12:12.869
Mussolini's great grandson now plays for Lazio, which is the same club that Gattuso is the coach at.

3511
03:12:12.969 --> 03:12:13.990
I love that video.

3512
03:12:14.210 --> 03:12:15.611
Like that's such a good video.

3513
03:12:15.672 --> 03:12:17.613
It's so applicable in so many life situations.

3514
03:12:17.653 --> 03:12:18.114
Classic meme.

3515
03:12:18.314 --> 03:12:19.355
And this is one of them, right?

3516
03:12:19.395 --> 03:12:22.658
The Valley splitting traditionally, it's kind of a crap shoot.

3517
03:12:22.878 --> 03:12:23.078
Yeah.

3518
03:12:23.158 --> 03:12:23.399
Okay.

3519
03:12:23.639 --> 03:12:24.099
Okay.

3520
03:12:24.139 --> 03:12:29.644
Um, in this paper, the one that's in nature in the supplement, they have like a 70 page supplement that they've uploaded.

3521
03:12:30.285 --> 03:12:31.646
Um, cause there was a lot of work that was done.

3522
03:12:32.207 --> 03:12:32.387
Um,

3523
03:12:33.695 --> 03:12:34.876
Let's look at this latest result.

3524
03:12:34.976 --> 03:12:38.618
It shows a valley splitting of 1.8 millielectron volts.

3525
03:12:39.019 --> 03:12:41.280
The other one was 300, so that would be 0.3.

3526
03:12:41.900 --> 03:12:45.963
We're going from 0.3, which was the best that they had, to now 1.8 and 1.

3527
03:12:46.443 --> 03:12:49.606
They're saying typical values of the valley splitting.

3528
03:12:50.126 --> 03:12:53.008
Crucially, they don't show a distribution.

3529
03:12:53.128 --> 03:12:59.052
What they say is that given our error rate is so low, you can tell that it's mostly...

3530
03:13:00.276 --> 03:13:01.357
going to be around these values.

3531
03:13:01.517 --> 03:13:01.757
Okay.

3532
03:13:01.897 --> 03:13:02.597
Okay.

3533
03:13:02.697 --> 03:13:04.058
It is no longer a problem.

3534
03:13:04.098 --> 03:13:04.478
Yeah.

3535
03:13:04.618 --> 03:13:06.619
And this is highlighted by the reviewers.

3536
03:13:07.600 --> 03:13:08.760
Again, this is a nature paper.

3537
03:13:08.780 --> 03:13:08.940
Right.

3538
03:13:09.040 --> 03:13:09.220
Right.

3539
03:13:09.240 --> 03:13:11.061
So you can read the reviewer report.

3540
03:13:11.161 --> 03:13:11.501
Yeah.

3541
03:13:11.762 --> 03:13:19.205
And the reviewer says that the author state in a certain line that the conventional concerns such as valley splitting are no longer limiting.

3542
03:13:19.845 --> 03:13:23.767
Attributing this to quantum well, which is engineered to increase valley splitting.

3543
03:13:24.348 --> 03:13:24.448
Okay.

3544
03:13:24.468 --> 03:13:24.668
Okay.

3545
03:13:25.368 --> 03:13:30.170
And then he says, if confirmed, this would represent a significant advance for electron spin qubits.

3546
03:13:30.710 --> 03:13:30.950
Okay?

3547
03:13:30.990 --> 03:13:33.231
If this is true, this is a big deal.

3548
03:13:33.311 --> 03:13:34.732
Why is it shoved in the supplement?

3549
03:13:34.792 --> 03:13:36.432
It's kind of what he's saying.

3550
03:13:36.452 --> 03:13:36.612
Right?

3551
03:13:36.652 --> 03:13:40.054
And then he says, the current evidence, he says, the current evidence is not enough.

3552
03:13:40.994 --> 03:13:48.737
And you need to show, like, you know, I would expect, for example, a statistical analysis of valley splitting across devices.

3553
03:13:48.877 --> 03:13:49.097
Right.

3554
03:13:49.137 --> 03:13:50.958
So it's like, maybe give me a distribution.

3555
03:13:51.098 --> 03:13:51.298
Right.

3556
03:13:52.075 --> 03:13:54.636
You know, he's basically saying, like, how do you do that?

3557
03:13:54.897 --> 03:13:55.157
Right.

3558
03:13:55.317 --> 03:13:59.319
And part of the argument might be, well, now that we're going private, it's partly proprietary.

3559
03:13:59.339 --> 03:14:00.620
And that's exactly the response.

3560
03:14:00.660 --> 03:14:03.281
The response from HRL is, I'm not telling you.

3561
03:14:03.481 --> 03:14:06.023
Because that's kind of the juice.

3562
03:14:06.063 --> 03:14:06.263
Yeah.

3563
03:14:06.643 --> 03:14:07.563
I mean, that is the juice.

3564
03:14:07.583 --> 03:14:07.824
Yeah.

3565
03:14:07.864 --> 03:14:08.504
Yeah.

3566
03:14:08.724 --> 03:14:12.526
It certainly shows that it's possible, which is great for the spin community in general.

3567
03:14:12.566 --> 03:14:12.746
Right.

3568
03:14:12.906 --> 03:14:13.126
Right.

3569
03:14:13.166 --> 03:14:15.588
Because it's not an insurmountable, like...

3570
03:14:16.248 --> 03:14:17.849
2 plus 2 equals 5 problem.

3571
03:14:17.889 --> 03:14:18.890
It is certainly possible.

3572
03:14:19.550 --> 03:14:32.316
And the response there to the reviewers is, we have instead substantiated our claim that value splitting is not an impediment with circumstantial evidence like the lack of multiple frequencies in your exchange oscillations.

3573
03:14:32.617 --> 03:14:38.980
Basically, all of these other little things are saying that if value splitting was still a problem, I would notice it in all of these other plots.

3574
03:14:39.100 --> 03:14:43.242
There's derivative measurements you make that identify it, whether it's there or not.

3575
03:14:43.262 --> 03:14:44.582
Yeah, and it's clearly not there.

3576
03:14:44.602 --> 03:14:45.123
It's not there.

3577
03:14:45.163 --> 03:14:53.186
And unfortunately, the proprietary nature of that information prevents a complete discussion of those aspects.

3578
03:14:53.206 --> 03:14:54.807
We got them.

3579
03:14:55.087 --> 03:14:56.888
We got them.

3580
03:14:57.128 --> 03:14:58.168
It's kind of interesting, right?

3581
03:14:58.228 --> 03:14:59.549
It's like another aspect.

3582
03:14:59.609 --> 03:15:01.069
It sometimes goes under the radar.

3583
03:15:04.307 --> 03:15:05.668
Just putting it in the supplement.

3584
03:15:06.008 --> 03:15:08.670
But the reviewer noticed and he brought it up.

3585
03:15:09.050 --> 03:15:12.792
And that's like a real – I mean based on the history we've talked about, right?

3586
03:15:13.113 --> 03:15:22.318
That's been the historical reason why the neutral items people or whoever, the trapped items people have been like, this is not going to happen.

3587
03:15:22.338 --> 03:15:32.085
Because you have to tell me how when we have naturally occurring silicon between isotope 28 and 29 and they have these six valleys –

3588
03:15:33.245 --> 03:15:43.230
which means that you are going to have this exponentially exploding calculation you have to do because you can't control where your thingy is the way you want it to.

3589
03:15:44.790 --> 03:15:48.132
That's like you have to solve that problem before I'm going to pay attention.

3590
03:15:48.672 --> 03:15:50.133
And they just kind of were like, yeah, we solved it.

3591
03:15:50.153 --> 03:15:52.194
But that's in the supplement.

3592
03:15:52.214 --> 03:15:53.074
It's in the supplement, right.

3593
03:15:53.394 --> 03:15:57.396
And it's funny because the isotopic enrichment part, that's an open secret.

3594
03:15:57.436 --> 03:15:58.076
That's how you do it.

3595
03:15:58.156 --> 03:15:58.396
Okay.

3596
03:15:58.436 --> 03:15:58.576
Right?

3597
03:15:58.737 --> 03:15:59.257
It's just like...

3598
03:16:00.164 --> 03:16:03.026
Yeah, that's a fundamental physics argument.

3599
03:16:03.066 --> 03:16:03.246
Sure.

3600
03:16:03.386 --> 03:16:09.289
You remove a bunch of magnetic spins from your substrate, and then you're no longer going to have the valley splitting part.

3601
03:16:09.669 --> 03:16:11.811
But that's different.

3602
03:16:12.031 --> 03:16:12.271
Right?

3603
03:16:12.311 --> 03:16:12.571
Yeah.

3604
03:16:12.831 --> 03:16:13.832
It's a little different.

3605
03:16:13.892 --> 03:16:14.792
It's a little different.

3606
03:16:15.173 --> 03:16:16.453
Right.

3607
03:16:16.513 --> 03:16:17.414
But that's proprietary.

3608
03:16:17.994 --> 03:16:18.154
Right?

3609
03:16:18.214 --> 03:16:19.715
But it certainly means that it's possible.

3610
03:16:19.755 --> 03:16:20.335
There's a chance.

3611
03:16:20.896 --> 03:16:25.338
And that, I think, spells great things for the spin qubits community in general.

3612
03:16:25.558 --> 03:16:28.360
Speaking of proprietary, we can get to our...

3613
03:16:29.624 --> 03:16:30.084
Our audit.

3614
03:16:30.244 --> 03:16:30.704
Our audit.

3615
03:16:30.744 --> 03:16:34.906
Which is also proprietary from First Principles audit.

3616
03:16:35.246 --> 03:16:37.267
So what are the strengths for silicon?

3617
03:16:37.347 --> 03:16:39.968
Well, silicon is a miracle material, right?

3618
03:16:40.208 --> 03:16:45.210
I mean, now that if you isotopically enrich it, you don't...

3619
03:16:45.250 --> 03:16:47.371
Apparently, the valley splitting is no longer a thing.

3620
03:16:47.431 --> 03:16:48.672
The negatives are no longer a thing.

3621
03:16:48.692 --> 03:16:50.032
Charge noise is no longer a thing.

3622
03:16:50.353 --> 03:16:54.474
If you fab it in a really nice way, like HRL has done, it's no longer a thing.

3623
03:16:55.635 --> 03:16:58.216
So seems to me like qubit quality...

3624
03:16:59.149 --> 03:16:59.749
Pretty high.

3625
03:17:00.030 --> 03:17:01.090
Quite nice.

3626
03:17:01.290 --> 03:17:01.710
Quite nice.

3627
03:17:02.711 --> 03:17:03.632
Let's go into control.

3628
03:17:05.293 --> 03:17:06.593
You see how I'm just breezing through these?

3629
03:17:06.773 --> 03:17:07.114
Yeah.

3630
03:17:07.594 --> 03:17:08.694
Pretty nice.

3631
03:17:09.175 --> 03:17:10.335
We've already explained it.

3632
03:17:10.536 --> 03:17:12.417
I already explained it.

3633
03:17:12.757 --> 03:17:15.378
In great three and a half hour long detail.

3634
03:17:15.698 --> 03:17:17.980
So it's very well established.

3635
03:17:18.060 --> 03:17:20.101
The cubic quality here is pretty great.

3636
03:17:20.801 --> 03:17:28.046
Spin qubits, DFS in this case, even with Lost Vincenzo, where you have the magnetic field and a single microwave thing.

3637
03:17:28.446 --> 03:17:28.686
Still,

3638
03:17:29.885 --> 03:17:31.607
It's just the spins going up and down.

3639
03:17:31.687 --> 03:17:32.848
You can pack them together.

3640
03:17:33.149 --> 03:17:36.092
You can use Exchange, which is DC only, to make them talk.

3641
03:17:36.112 --> 03:17:36.793
It's fundamental.

3642
03:17:37.033 --> 03:17:37.434
It's great.

3643
03:17:37.474 --> 03:17:38.815
Back to basics.

3644
03:17:39.136 --> 03:17:39.957
Now, for control.

3645
03:17:39.977 --> 03:17:40.217
Control.

3646
03:17:41.762 --> 03:17:44.484
The gate speeds are really fast.

3647
03:17:44.684 --> 03:17:47.426
Exchange-only gates execute in 1 to 10 nanoseconds.

3648
03:17:47.746 --> 03:17:57.674
So the same stuff that we liked about superconducting circuits, which is the fact that I can run shores pretty quickly in a matter of hours rather than a month or a year, I can still do that here, right?

3649
03:17:57.694 --> 03:17:57.914
Beautiful.

3650
03:17:57.934 --> 03:18:00.275
As long as I have enough qubits to go around.

3651
03:18:00.296 --> 03:18:03.578
They're actually faster in some cases with superconducting circuits.

3652
03:18:04.859 --> 03:18:06.460
And they use only baseband circuits.

3653
03:18:07.665 --> 03:18:08.906
The gates are all baseband.

3654
03:18:08.946 --> 03:18:09.727
It's all DC.

3655
03:18:09.807 --> 03:18:10.347
Yeah, right.

3656
03:18:10.367 --> 03:18:10.808
There's no AC.

3657
03:18:10.828 --> 03:18:12.549
So there's no AC leakage everywhere.

3658
03:18:13.110 --> 03:18:16.273
And I can, you know, isolate it from the system.

3659
03:18:16.293 --> 03:18:17.834
Although that'll get into scalability part.

3660
03:18:17.854 --> 03:18:18.555
So let me not go there.

3661
03:18:19.035 --> 03:18:20.697
Now, what are the negatives with control?

3662
03:18:22.038 --> 03:18:24.100
The negatives, there is one.

3663
03:18:25.184 --> 03:18:26.665
And that's where my job comes in.

3664
03:18:26.885 --> 03:18:27.726
Aha!

3665
03:18:28.247 --> 03:18:28.527
Okay?

3666
03:18:28.747 --> 03:18:31.770
If you've made it this long, you now will know what Krishna does.

3667
03:18:31.790 --> 03:18:35.813
Finally, you'll know what I do in my life when I'm not in this podcast studio.

3668
03:18:36.494 --> 03:18:43.380
So there's a skeleton in the closet here, which is I'm fabricating stuff at the limit of...

3669
03:18:45.502 --> 03:18:46.164
fabrication.

3670
03:18:47.125 --> 03:18:50.090
There's these gates, these wires are tens of nanometers.

3671
03:18:50.390 --> 03:18:52.854
They have to be done with this isotopically rich silicon.

3672
03:18:54.296 --> 03:18:57.882
And when I fabricate, you know, at the nanometer scale for transistors,

3673
03:18:58.724 --> 03:19:02.148
If a single transistor has a few extra atoms, not a big deal.

3674
03:19:02.308 --> 03:19:02.749
No big deal.

3675
03:19:02.989 --> 03:19:03.530
Not a big deal.

3676
03:19:04.130 --> 03:19:05.352
Here, it is a big deal.

3677
03:19:05.752 --> 03:19:17.045
Because if a single gate has a few extra atoms, is slightly bigger, slightly smaller, if there's a random charge noise hanging around, then the same settings that I used for one set...

3678
03:19:18.330 --> 03:19:23.774
Let's say I plus 0.4, minus 0.5, plus 0.652, whatever.

3679
03:19:24.635 --> 03:19:36.984
I can't use those same settings everywhere in my device because every single one of these electrodes, because of the fab disorder, there's going to be inherent noise in how that happens, right?

3680
03:19:37.385 --> 03:19:41.288
So you would have to tune up this device.

3681
03:19:43.185 --> 03:20:00.812
For every single qubit, you'd have to figure out exactly the right settings to get three isolated, to understand how long I have to wait to make an exchange gate, to understand what is the voltage, what is the current when there are two.

3682
03:20:01.313 --> 03:20:08.675
When I do that polyspin blockade, when I do the readout, where I'm shoving two electrons into a single thing, how do I actually do that?

3683
03:20:08.755 --> 03:20:09.796
How long do I have to wait?

3684
03:20:10.977 --> 03:20:13.840
What corresponds to two electrons being in there versus one?

3685
03:20:13.880 --> 03:20:15.101
Because I'm reading a current, right?

3686
03:20:15.701 --> 03:20:28.052
And so, I mean, you could have a PhD physicist do this by hand, which, fine, for like small enough for the 2023 paper, where there's like six electrons, fine, you could do that.

3687
03:20:29.053 --> 03:20:33.216
Pretty soon, if you want to scale this thing, it is going to get insane, right?

3688
03:20:33.296 --> 03:20:37.220
It would take a human lifetime to tune up a million qubits by hand.

3689
03:20:38.156 --> 03:20:38.416
Yeah.

3690
03:20:38.636 --> 03:20:38.877
Right?

3691
03:20:38.977 --> 03:20:40.017
Yeah.

3692
03:20:40.458 --> 03:20:42.579
And so you are the qubit tuner.

3693
03:20:42.800 --> 03:20:46.162
Yes, I am part of the qubit tuning team.

3694
03:20:46.362 --> 03:20:48.524
I used to be part of the qubit tuning team at HRL.

3695
03:20:48.564 --> 03:20:51.006
And that's still something that I do at Duroc now.

3696
03:20:51.066 --> 03:20:52.067
QTT.

3697
03:20:52.107 --> 03:20:53.668
So here's how it actually works.

3698
03:20:53.748 --> 03:20:57.411
I'll just show you some of the supplement of this paper that goes into that kind of stuff.

3699
03:20:57.731 --> 03:21:00.473
The first thing you do is you make a...

3700
03:21:01.963 --> 03:21:03.784
Dot charge sensor is what they call it.

3701
03:21:03.804 --> 03:21:05.426
This is your single electron transistor.

3702
03:21:05.686 --> 03:21:07.767
So you initiate the single electron transistor.

3703
03:21:08.047 --> 03:21:10.849
That way you can sense what the hell is happening in my device.

3704
03:21:11.429 --> 03:21:14.732
Then I start loading my dots.

3705
03:21:15.531 --> 03:21:16.872
Before, there's no electrons.

3706
03:21:17.312 --> 03:21:22.954
And then now I want to load exactly one electron into each, or in some cases, an odd number of electrons into each.

3707
03:21:23.294 --> 03:21:27.696
That way the electrons pair up, and only the thing that is missing is going to be talking and doing the stuff.

3708
03:21:28.116 --> 03:21:31.378
In order to do that, what I do is I toggle the voltages.

3709
03:21:31.918 --> 03:21:37.200
And when I toggle the voltages, the electrons are going to tunnel and go bloop into one, bloop into another.

3710
03:21:37.500 --> 03:21:41.602
And every time that happens, my single electron transistor is going to move

3711
03:21:42.780 --> 03:21:45.301
And you see on the bottom, the C and D?

3712
03:21:45.661 --> 03:21:45.902
Yes.

3713
03:21:46.702 --> 03:21:49.163
Those are images that show these tunneling events.

3714
03:21:49.683 --> 03:21:55.946
Like every time an electron is moving from one room to another, the charge sensor is going to move.

3715
03:21:55.966 --> 03:21:57.547
And so my current is going to be a different.

3716
03:21:58.093 --> 03:22:14.325
color it's going to be a different value that's going to manifest as a different color and so the two axes are my voltages like i'm scanning this voltage and i'm scanning this voltage and there's going to be an event that's going to show up as a streak and those streaks are going to tell me what the settings are that i need to implement

3717
03:22:15.726 --> 03:22:28.841
Finally, once I have the correct settings, then I go into creating my polysplenball blockade, my readout, where I shove two electrons into a single confinement well to see if there's two electrons, then I get one...

3718
03:22:29.858 --> 03:22:30.638
value of current.

3719
03:22:30.778 --> 03:22:32.459
That's the histogram on the right-hand side.

3720
03:22:32.879 --> 03:22:35.140
If there's one electron, then I get another value of current.

3721
03:22:35.460 --> 03:22:39.221
And so those two then tell me, hey, if I got this current, that means I'm a one.

3722
03:22:39.541 --> 03:22:41.182
If I got this current, that means I'm a zero.

3723
03:22:41.582 --> 03:22:45.123
And then finally, I then tune the other axes to get full blocks for your control.

3724
03:22:45.503 --> 03:22:47.224
So this is the sort of

3725
03:22:48.796 --> 03:22:52.779
path that you would have to take for every single qubit in order to make it work.

3726
03:22:52.999 --> 03:22:53.179
Right.

3727
03:22:53.219 --> 03:22:56.141
And each of them have their own subsequent sub steps.

3728
03:22:56.181 --> 03:22:57.602
Like, that's a very brief.

3729
03:22:57.742 --> 03:22:58.463
That's a very brief.

3730
03:22:58.483 --> 03:23:01.985
But this whole thing is going to take like two hours for like a human being.

3731
03:23:02.166 --> 03:23:02.406
Okay.

3732
03:23:02.546 --> 03:23:02.846
Okay.

3733
03:23:02.926 --> 03:23:03.867
Ain't nobody got time for that.

3734
03:23:04.067 --> 03:23:04.247
Right.

3735
03:23:04.307 --> 03:23:04.467
Right.

3736
03:23:04.487 --> 03:23:04.647
Right.

3737
03:23:05.088 --> 03:23:05.788
For each qubit.

3738
03:23:05.828 --> 03:23:06.028
Yeah.

3739
03:23:06.048 --> 03:23:06.729
For each qubit.

3740
03:23:06.909 --> 03:23:07.229
Right.

3741
03:23:07.409 --> 03:23:07.890
Yeah.

3742
03:23:09.241 --> 03:23:09.922
So you use AI.

3743
03:23:10.102 --> 03:23:10.762
Yeah, of course.

3744
03:23:11.222 --> 03:23:11.523
Of course.

3745
03:23:11.803 --> 03:23:12.143
Of course.

3746
03:23:12.303 --> 03:23:12.984
Of course.

3747
03:23:13.164 --> 03:23:18.828
Especially because like the bottom part where you're like finding the edges and you're finding the like, it's just an image.

3748
03:23:19.048 --> 03:23:19.248
Right.

3749
03:23:19.368 --> 03:23:20.549
That I'm looking for streaks.

3750
03:23:20.769 --> 03:23:20.890
Right.

3751
03:23:20.910 --> 03:23:21.030
Right.

3752
03:23:21.758 --> 03:23:22.658
Object detection.

3753
03:23:23.299 --> 03:23:24.579
The computers have vision now.

3754
03:23:24.619 --> 03:23:24.839
Yeah.

3755
03:23:25.219 --> 03:23:26.040
Yes, exactly.

3756
03:23:26.080 --> 03:23:26.420
Computer.

3757
03:23:26.620 --> 03:23:30.541
So that's kind of some of the stuff that I worked on with the automation team.

3758
03:23:30.761 --> 03:23:32.742
Makes sense.

3759
03:23:33.262 --> 03:23:45.066
This is the machine learning sort of roadmap on how to get from the scan, where you get these tunneling events, all the way to, okay, what are the voltages that create those tunneling events?

3760
03:23:45.126 --> 03:23:46.847
And then what are the settings that I need to create?

3761
03:23:47.267 --> 03:23:47.867
This is a DETR.

3762
03:23:52.534 --> 03:23:53.757
detection transformer.

3763
03:23:54.258 --> 03:23:54.719
So it's a...

3764
03:23:56.701 --> 03:24:04.367
hybrid between a convolutional neural network, like a ResNet that actually does most of the object detection and stuff.

3765
03:24:04.507 --> 03:24:13.535
But then you feed that stuff into a transformer, then then uses attention to then create like relationships between all of these lines to tell me where the stuff is.

3766
03:24:13.595 --> 03:24:14.615
God, this is so good.

3767
03:24:14.675 --> 03:24:14.956
Okay.

3768
03:24:14.976 --> 03:24:19.259
So now you actually finally have a good idea.

3769
03:24:19.419 --> 03:24:21.621
This chart, I understand.

3770
03:24:21.641 --> 03:24:22.342
This one makes sense.

3771
03:24:22.582 --> 03:24:26.105
But I think it's a very, what's really cool about, or important about, not important.

3772
03:24:26.125 --> 03:24:26.405
Yeah.

3773
03:24:26.565 --> 03:24:29.814
What's interesting about this is that of everything we talked about,

3774
03:24:30.893 --> 03:24:34.555
To get to this point, every aspect of it is this complex.

3775
03:24:35.296 --> 03:24:37.677
And we're just talking about a sliver, a slice.

3776
03:24:37.837 --> 03:24:38.778
That's a very good point.

3777
03:24:39.438 --> 03:24:43.281
Every single aspect, which is why there's 250 authors.

3778
03:24:43.561 --> 03:24:52.647
Because everything is so – you have to be so deeply understanding of the physics aspects of it and then whatever the applied avenue that you're dealing with.

3779
03:24:52.707 --> 03:24:53.988
Are you a materials person?

3780
03:24:54.428 --> 03:24:58.151
Are you working in algorithms and computation at the chip level?

3781
03:24:58.511 --> 03:25:00.412
Are you working on those at the –

3782
03:25:00.952 --> 03:25:25.164
the external are you are you building the software that lets me right like do this do this actually because it's just because you have the chip doesn't mean you can do anything with it there's so many and every one of them has a depth of knowledge and execution necessary that i think people really can underestimate when we don't work in these things and we sort of will go through a paper and we'll explain it and it's like yeah we're taking away the things but like

3783
03:25:26.435 --> 03:25:32.680
A lot of people have worked very, very, very, very hard in an area that very few people can even work in.

3784
03:25:32.820 --> 03:25:33.860
Yeah.

3785
03:25:34.061 --> 03:25:35.201
To accomplish that.

3786
03:25:36.222 --> 03:25:41.546
So that's like – because the tuning piece, again, it's one sliver.

3787
03:25:41.566 --> 03:25:43.407
But it's a very important – Yeah.

3788
03:25:43.467 --> 03:25:45.269
I mean it's part of the scalability argument.

3789
03:25:45.289 --> 03:25:45.489
Right.

3790
03:25:45.589 --> 03:25:45.829
Right.

3791
03:25:45.909 --> 03:25:46.109
Right.

3792
03:25:46.269 --> 03:25:47.570
Of the three layers of the criterion.

3793
03:25:47.630 --> 03:25:48.891
Anyway, I'm just trying to give you props.

3794
03:25:48.931 --> 03:25:49.512
But like that –

3795
03:25:50.112 --> 03:26:08.860
it's dude this is so guys i'm really actually just like on a personal note i'm very happy that we did this because now my podcast partner actually knows what i do on a date this is as a day job right and like now i know when we go out and we're people i'm like you know what he does and i'll be able to give him the spiel yeah exactly

3796
03:26:09.702 --> 03:26:10.903
So that was the control part.

3797
03:26:11.083 --> 03:26:11.203
Okay.

3798
03:26:11.243 --> 03:26:14.105
And although towards the end, we kind of got into scalability.

3799
03:26:14.145 --> 03:26:14.305
Yeah.

3800
03:26:14.425 --> 03:26:18.367
Which is like, if we want to build a bigger thing, you better be able to tune that thing autonomously.

3801
03:26:18.707 --> 03:26:18.867
Right?

3802
03:26:18.927 --> 03:26:21.569
You don't want a human being there sitting there like a monkey doing this.

3803
03:26:21.729 --> 03:26:22.269
100%.

3804
03:26:22.329 --> 03:26:24.391
And so finally, we get into scalability and economics.

3805
03:26:24.431 --> 03:26:27.813
And this is the kill shot for silicon.

3806
03:26:27.913 --> 03:26:30.194
If you want to build 100,000-cubit trapped...

3807
03:26:30.614 --> 03:26:36.440
Ion machine, you're going to have to invent a hundred thousand laser optical miracle.

3808
03:26:37.281 --> 03:26:42.567
But if you want a million superconducting qubits, you're going to have to build a warehouse sized priostat.

3809
03:26:43.107 --> 03:26:43.628
Boo.

3810
03:26:43.988 --> 03:26:45.610
But if you want a million spin qubits...

3811
03:26:46.467 --> 03:26:50.069
You just put it on a standard 300 millimeter silicon wafer.

3812
03:26:51.450 --> 03:27:00.676
You run it through the exact same photolithography machines at TSMC, ASML, Intel, that made the processor in your iPhone.

3813
03:27:01.236 --> 03:27:02.197
And there you'll have it.

3814
03:27:02.998 --> 03:27:03.218
Right.

3815
03:27:03.678 --> 03:27:05.199
Scaling is the key.

3816
03:27:05.659 --> 03:27:05.839
Yeah.

3817
03:27:05.999 --> 03:27:07.320
And scaling is the future.

3818
03:27:07.460 --> 03:27:08.721
Yeah.

3819
03:27:09.041 --> 03:27:11.023
HRL is not the only one that is pursuing this stuff.

3820
03:27:11.123 --> 03:27:14.605
So I want to give a shout out to some of the other players in the space.

3821
03:27:15.045 --> 03:27:24.567
Intel had a really amazing talk after Thaddeus' talk at the APS March meeting that showed uniformity in a lot of their fab.

3822
03:27:24.587 --> 03:27:26.267
I mean, they're really good at fab, right?

3823
03:27:27.067 --> 03:27:32.528
And they could make their chips along with like 16 metal layers of back end, which is kind of crazy.

3824
03:27:32.868 --> 03:27:35.969
And they had a roadmap to scale up to larger qubits.

3825
03:27:35.989 --> 03:27:40.810
So there's already scaling to larger numbers of qubits coming in from Intel.

3826
03:27:41.670 --> 03:27:45.753
And then, of course, there is Dirac, which is where I am at right now.

3827
03:27:45.793 --> 03:27:52.937
This is an Australian startup that is trying to make millions of spin qubits on a single silicon chip.

3828
03:27:53.117 --> 03:27:54.798
It's a great place to work, to be honest.

3829
03:27:55.138 --> 03:27:59.041
And Dirac also publishes in Nature on the regular.

3830
03:27:59.101 --> 03:28:04.364
So on the next slide, we've got just a few of the ones that came out in the last two years.

3831
03:28:05.084 --> 03:28:27.930
um spin qubit control with um a millikelvin cmos chip so they're getting into the cryo cmos type of stuff um they've got really high fidelity they're getting into that and they've got high fidelity spin qubit operation and initialization above one kelvin so they're trying to do things without going even into the millikelvin stage it's an open problem right like do you even need um

3832
03:28:29.515 --> 03:28:39.100
You could do LD qubits, Lost D Vincenzo qubits, but the energy split is big enough that even at one Kelvin, the temperature is lower than that energy split.

3833
03:28:39.160 --> 03:28:42.462
So spin qubits are really making a resurgence, I think.

3834
03:28:43.102 --> 03:28:43.322
And...

3835
03:28:45.138 --> 03:28:48.803
I think you don't have to invent a supply chain is the point.

3836
03:28:49.003 --> 03:28:49.384
Yeah.

3837
03:28:49.624 --> 03:28:51.446
The supply chain already exists.

3838
03:28:51.587 --> 03:28:59.617
We're piggybacking off of 60 years of Moore's law and trillions of dollars of CMOS and silicon manufacturing infrastructure.

3839
03:29:01.038 --> 03:29:06.161
there's a reason why your laptop is a miracle of engineering, and yet it's still actually kind of cheap.

3840
03:29:06.381 --> 03:29:07.061
Yeah.

3841
03:29:07.161 --> 03:29:21.208
If you think about it, like people who build computers, they have to do the same drastic, like the people who are at Apple and like Dell, they have the same level of like crazy specific knowledge, right?

3842
03:29:21.528 --> 03:29:25.250
But they're making laptops on the Chief because they can scale, right?

3843
03:29:25.270 --> 03:29:25.570
100%.

3844
03:29:26.494 --> 03:29:39.448
And the point is that when manufacturing that first wafer that's going to get you that first silicon quantum computer at scale that is fault tolerant and all that other stuff, that first wafer is going to be hella expensive.

3845
03:29:39.468 --> 03:29:40.009
Yeah, yeah.

3846
03:29:40.089 --> 03:29:40.369
Okay?

3847
03:29:40.710 --> 03:29:41.611
And it's still not there yet.

3848
03:29:41.891 --> 03:29:42.952
Yep.

3849
03:29:43.252 --> 03:29:44.554
But once you get that one wafer...

3850
03:29:44.614 --> 03:29:47.056
But once you get that one wafer, the second wafer...

3851
03:29:47.828 --> 03:29:48.649
It's going to be a joke.

3852
03:29:49.229 --> 03:29:52.652
The path of acceleration is going to be so much faster if you can do it on a silicon wafer.

3853
03:29:52.712 --> 03:29:52.912
Yeah.

3854
03:29:53.113 --> 03:29:58.237
Because we already, it's already all there, which is, I can't overstate that as a part of this.

3855
03:29:58.317 --> 03:29:58.557
Yeah.

3856
03:29:59.338 --> 03:29:59.458
Um,

3857
03:30:00.215 --> 03:30:10.722
It's part of the reason why the acceleration of AI has been so quick because NVIDIA has already been building GPUs, which were the substrate that's really good for a lot of these transformer algorithms, the matrix multiplication.

3858
03:30:10.983 --> 03:30:15.205
And so imagine that we did not have GPUs at the level that NVIDIA was today.

3859
03:30:15.226 --> 03:30:15.486
Good point.

3860
03:30:15.946 --> 03:30:16.106
Right?

3861
03:30:16.166 --> 03:30:18.108
We would not have seen the acceleration of AI that quickly.

3862
03:30:18.248 --> 03:30:19.208
And it wouldn't have been that big a deal.

3863
03:30:19.228 --> 03:30:21.090
But they already – it's global.

3864
03:30:21.310 --> 03:30:21.570
Mm-hmm.

3865
03:30:21.990 --> 03:30:24.250
It's already been – they have the distribution partners.

3866
03:30:25.051 --> 03:30:26.111
Anyway, you get the idea.

3867
03:30:26.431 --> 03:30:30.992
So that's how I make the connection here.

3868
03:30:32.612 --> 03:30:49.315
As someone coming from more of the technology and like operational context in the real world, it's like as soon as you cross that Rubicon, again, there's going to be the battle at the chip makers with their other business lines for time.

3869
03:30:49.335 --> 03:30:49.755
Yeah.

3870
03:30:50.367 --> 03:30:53.723
But, you know, a quantum chip...

3871
03:30:54.997 --> 03:30:59.278
It's going to be hard to argue why that shouldn't be at the front of the line.

3872
03:30:59.338 --> 03:30:59.738
Exactly.

3873
03:30:59.838 --> 03:31:01.078
And I mean, there's a...

3874
03:31:01.598 --> 03:31:08.200
So IBM has its own chip-making facilities, which is, I think, one of the reasons why it probably acquired HRL.

3875
03:31:08.280 --> 03:31:09.200
It also probably...

3876
03:31:09.820 --> 03:31:16.621
I'm not going to speak for IBM, but maybe I am a little, in saying that they may see the writing on the wall when it comes to superconducting qubits.

3877
03:31:16.961 --> 03:31:20.862
I mean, there was... You know, at APS, actually, I should mention that Northrop Grumman...

3878
03:31:21.162 --> 03:31:35.530
at a talk where they showed they used the sort of same trick that these guys are using with Exchange Only, where they had superconducting qubits, but you could rig them up to create qubits where there were single triplets made out of transmons.

3879
03:31:36.350 --> 03:31:39.892
But now I only have to communicate with them using DC.

3880
03:31:40.153 --> 03:31:42.654
Now, that's all fine, but it's still not in silicon, right?

3881
03:31:43.114 --> 03:31:45.235
And it's still massive, still big.

3882
03:31:45.656 --> 03:31:49.818
So you still have that scaling problem, even though maybe you don't have the wiring problem anymore.

3883
03:31:49.838 --> 03:31:49.938
Yeah.

3884
03:31:50.804 --> 03:32:15.375
there's still an advantage in using silicon um and because silicon is just the bread and butter of our economy right it is the best um so finally we do have our ffp audit that we are going to um put on spins the last overlay of the day yeah so uh qubit quality 10 out of 10 yep easily electron spins are dope yep

3885
03:32:16.106 --> 03:32:26.329
whether it's lost even Chenzo or exchange only cubit control again, 10 out of 10, you're using maybe a single microwave that's going through for lost even Chenzo.

3886
03:32:26.389 --> 03:32:34.171
And then your baseband pulses or just only baseband pulses with exchange only again, all DC amazing.

3887
03:32:35.151 --> 03:32:44.074
If you can, if you can handle the isotopic enrichment and you can handle the Valley States like HRL has, you're good to go with 10 out of 10, which is now totally solvable.

3888
03:32:44.154 --> 03:32:44.394
So yeah,

3889
03:32:44.694 --> 03:32:45.356
That's great to know.

3890
03:32:45.656 --> 03:32:47.921
And scalability and economics, 10,000 out of 10.

3891
03:32:48.768 --> 03:32:49.429
It's obvious.

3892
03:32:49.929 --> 03:32:52.371
The total is 10,020 out of 30.

3893
03:32:53.272 --> 03:32:59.897
Just to bring it up again, neutral atoms was at negative 3,000 in our proprietary criteria.

3894
03:33:00.018 --> 03:33:13.289
Just saying to the German guy who is not listening, but if somebody knows the Germans who work on neutral atoms, please send this to them because I really hope they see all the comments that are coming in.

3895
03:33:14.990 --> 03:33:15.811
But silicon is key.

3896
03:33:15.871 --> 03:33:16.151
And so...

3897
03:33:18.027 --> 03:33:25.319
There's a reason why other modalities in classical computing like vacuum tubes and electric relays are in the museums.

3898
03:33:25.399 --> 03:33:26.861
And it's because the transistor took over.

3899
03:33:27.462 --> 03:33:30.708
And so I firmly believe that even though silicon might not be the first...

3900
03:33:31.244 --> 03:33:33.104
quantum computer to achieve fault tolerance.

3901
03:33:33.164 --> 03:33:40.386
And there might be a world where ions get there first or superconducting computers get there first or even neutral atoms get there first.

3902
03:33:40.806 --> 03:33:43.547
I don't think it is going to be the future quantum computer.

3903
03:33:44.247 --> 03:33:51.829
Once it's achieved, I think silicon is going to be the one that actually gets scaled because it's cheap and it's easy to make.

3904
03:33:52.589 --> 03:33:53.669
We've seen this happen.

3905
03:33:54.189 --> 03:33:55.029
Perfect example.

3906
03:33:55.109 --> 03:33:58.150
MySpace was first, but we still all use all.

3907
03:33:58.430 --> 03:34:24.692
facebook related phase because being first doesn't mean being what becomes the standard yeah exactly and now you can finally understand the ai generated song that was in the beginning of this podcast um it i don't have the backstory for it but if somebody has the backstory for it from the group chat it was just posted in the group chat and i was like this is dope i'm gonna use this um a few points of note on that song um it says exchange only cubits

3908
03:34:25.919 --> 03:34:27.980
Because I think the AI doesn't know how to pronounce it.

3909
03:34:28.060 --> 03:34:30.042
And also Scalable Quantum.

3910
03:34:30.142 --> 03:34:30.642
Scalable.

3911
03:34:30.782 --> 03:34:31.343
Scalable.

3912
03:34:31.463 --> 03:34:32.624
So you'll hear that.

3913
03:34:32.884 --> 03:34:33.704
It's a bonix.

3914
03:34:33.724 --> 03:34:35.486
It's fine.

3915
03:34:35.766 --> 03:34:36.566
You said it, not me.

3916
03:34:37.267 --> 03:34:37.927
That's true.

3917
03:34:37.967 --> 03:34:38.608
That is true.

3918
03:34:38.728 --> 03:34:42.170
And before I end my segment, I'd just like to thank some of my co-authors.

3919
03:34:42.230 --> 03:34:43.551
Now there's 250 of them.

3920
03:34:43.951 --> 03:34:45.473
I'm not going to read out every single one.

3921
03:34:45.513 --> 03:34:51.857
But there are a few that I will name that I had personal relations with at HRL and continue to have personal relations with.

3922
03:34:52.277 --> 03:34:57.180
Today, first, the three corresponding authors, Thaddeus Ladd, Jacob Blumhoff, and Matt Reed.

3923
03:34:57.540 --> 03:35:04.445
Thaddeus Ladd very generously sold me one of his extra copies of the Nature Physical.

3924
03:35:04.565 --> 03:35:05.745
He bought like 10 of them.

3925
03:35:06.086 --> 03:35:10.548
I think he's very excited that this is finally seeing the light of day, obviously.

3926
03:35:10.829 --> 03:35:12.670
I hope you made it this far.

3927
03:35:13.230 --> 03:35:20.995
He's also one of the people responsible for actually getting me to APS because the deadline was on a Friday.

3928
03:35:21.015 --> 03:35:21.115
Yeah.

3929
03:35:21.635 --> 03:35:23.237
I didn't know because I don't keep track of these things.

3930
03:35:23.257 --> 03:35:25.179
I thought somebody would tell me that he's told me.

3931
03:35:25.439 --> 03:35:29.263
He emailed everyone like, hey, is everyone like signed up and like taken care of?

3932
03:35:29.283 --> 03:35:29.823
And I'm like, what?

3933
03:35:29.903 --> 03:35:31.305
And then it's like, dude, there's an hour left.

3934
03:35:31.585 --> 03:35:32.626
And I'm like scrambling.

3935
03:35:32.846 --> 03:35:35.409
And he helped me figure out like what session to be in and things like that.

3936
03:35:35.449 --> 03:35:36.850
So thanks for that.

3937
03:35:36.950 --> 03:35:38.372
Also, like the nature of...

3938
03:35:39.433 --> 03:35:42.535
Getting physical copies of nature is like a mom and pop shop.

3939
03:35:42.635 --> 03:35:42.995
Yeah.

3940
03:35:43.035 --> 03:35:43.376
Yeah.

3941
03:35:43.396 --> 03:35:45.297
Like you got to, you got to like email someone.

3942
03:35:45.317 --> 03:35:47.738
Then they email you back being like, Hey, what did you want?

3943
03:35:48.119 --> 03:35:49.480
And then you're like, I want a copy.

3944
03:35:49.500 --> 03:35:53.762
And then they email you back a form being like, okay, fill out this form manually.

3945
03:35:54.123 --> 03:35:54.943
And then they send it.

3946
03:35:55.023 --> 03:35:58.285
And a lot of my coauthors who've got these, they got water damage.

3947
03:35:58.706 --> 03:35:59.126
Oh, wow.

3948
03:35:59.246 --> 03:36:05.150
Like I didn't even know mail got water damage these days, but somehow like he got 10 of these copies.

3949
03:36:05.270 --> 03:36:06.471
Eight of them had water damage.

3950
03:36:07.171 --> 03:36:08.352
This one doesn't.

3951
03:36:08.372 --> 03:36:10.494
This one's in good condition.

3952
03:36:10.854 --> 03:36:11.915
This one is in great.

3953
03:36:12.135 --> 03:36:19.582
And we're going to encase it in a cryostat so that it remains in good quality because this is a big deal.

3954
03:36:19.622 --> 03:36:19.882
Yeah.

3955
03:36:20.263 --> 03:36:20.463
Yeah.

3956
03:36:20.483 --> 03:36:21.384
So a few other people.

3957
03:36:21.424 --> 03:36:24.767
Patrick Harrington, congratulations on being a new father.

3958
03:36:25.607 --> 03:36:44.982
um cliff plesha thank you for uh sending me some of the videos from ap s so i could relive the the big talks tina garcia um thomas harris and kevin he these guys uh these guys kept my fridge cold at hrl for me so i didn't have to go and refill the liquid nitrogen every week that was pretty great um

3959
03:36:46.832 --> 03:36:59.061
Cameron Jennings, Paul Jerger, Stephen Carr, John Carpenter, who's the artist behind this, Faustin Carter, Matthew Borselli, who's been working on SpinCubits at HRL for a very, very long time.

3960
03:36:59.502 --> 03:37:01.583
So congratulations on this paper.

3961
03:37:01.904 --> 03:37:03.305
Kevin Chen, Adam Daly.

3962
03:37:03.405 --> 03:37:05.747
Adam Daly taught me everything that I know about spin.

3963
03:37:06.507 --> 03:37:32.822
dilution refrigerators and taught me how to like operate one keep it cold that was pretty great jp dotson galen gladhill who is a co-worker of mine now at durac so i see him every week and that's pretty fun aaron mitch jones um really great in like bringing me into the fold with the um hrl quantum project raj kati joseph kirkoff justin christensen who was a classmate of mine at ucla um

3964
03:37:33.782 --> 03:37:57.904
um phd and then we both ended up at hrl andrew pan matthew raker matthew raker had a great um like cubits class where he actually taught me from fundamentals from for its principles all right the exchange cubit worked things like that he was he was very patient with me that was this pod in future classes yeah uh rashan sajad christian snibel congrats on your second kid bosun

3965
03:37:58.805 --> 03:38:03.627
Skylar Turner and Alan Sinanian, who are both now colleagues of mine at Dirac.

3966
03:38:04.308 --> 03:38:05.628
Aaron Weinstein.

3967
03:38:06.068 --> 03:38:11.431
Aaron Weinstein was the first author of the 2023 paper, the Universal Logic one.

3968
03:38:11.471 --> 03:38:12.371
So props on that.

3969
03:38:12.431 --> 03:38:13.352
And then Adam Holmes.

3970
03:38:13.672 --> 03:38:15.873
And finally, the automation team that I was a part of.

3971
03:38:16.929 --> 03:38:41.537
um alwina lu she's a big fan of the podcast i hope you've listened all the way to where uh you can now hear your name i hope the sound is fixed i know you've been complaining about that let us know yeah let us know if it's fixed for you um ian jenkins joe kern um john maeda uh last no not last but uh definitely least i have to say sam mumford

3972
03:38:42.297 --> 03:38:43.839
We have a long history, this guy.

3973
03:38:45.080 --> 03:38:47.462
He was a classmate of mine at Princeton.

3974
03:38:47.683 --> 03:38:48.624
Okay.

3975
03:38:49.124 --> 03:38:52.047
So he lived down the hall from me in 1941.

3976
03:38:52.107 --> 03:38:53.088
Oh, really?

3977
03:38:53.108 --> 03:38:59.235
Yes, former Wilson College, then first college, then it got demolished, and now it's called Hobson College.

3978
03:38:59.315 --> 03:39:02.438
I don't know if 1941 Hall is going to make it back, but he lived.

3979
03:39:02.678 --> 03:39:24.561
down the street from me that's i'm not down the street literally down the hallway um uh so in freshman year so he was he was one of one of my first friends at princeton we took um physics classes together and he was in physics with me um he no you don't know him he never hung out at ivy he would i went around other places than ivy don't you don't you throw dirt on my name

3980
03:39:25.883 --> 03:39:52.525
he'd be hanging out with the uh with the engineers at charter um but he you know jokes aside very instrumental in bringing me up into the fold he was uh you know we're old friends and i hope you're listening to this one episode i know you don't like listening to it um but whatever you know it is what it is um so sam sam mumford and last um definitely not least um maybe most is theresa brecht

3981
03:39:53.357 --> 03:39:54.658
Long time fan of the pod.

3982
03:39:54.678 --> 03:39:55.999
Number one fan.

3983
03:39:56.679 --> 03:39:59.401
A patron of the podcast arts.

3984
03:39:59.561 --> 03:40:03.964
But more importantly, from a personal level, she was my boss at HRL.

3985
03:40:04.185 --> 03:40:06.226
And she was the best boss that I've ever had.

3986
03:40:06.566 --> 03:40:08.588
And she also took a chance on me.

3987
03:40:09.208 --> 03:40:34.225
with getting me into the spin qubits program because i started at hrl as um just a machine learning guy right and i was in the intelligence systems lab and i was telling you that like i was working on like these tiny bespoke machine learning projects wasn't really you know fitting my um ambition levels and like interest levels and then the quantum silicon team was um

3988
03:40:35.345 --> 03:40:39.506
in need of like machine learning people to do the automation stuff that we had just talked about.

3989
03:40:39.706 --> 03:40:41.247
And I joined that group.

3990
03:40:41.347 --> 03:40:47.509
And then finally, when, when time came, I asked her, he sort of like formally put me into the HRL quantum team, which she did.

3991
03:40:47.549 --> 03:40:48.409
She gave me a chance.

3992
03:40:48.709 --> 03:40:49.629
Um, and I ran with it.

3993
03:40:49.649 --> 03:40:52.950
And so because of her, really, I'm on this, I'm on this paper.

3994
03:40:52.990 --> 03:40:54.531
So thank you, Teresa for that.

3995
03:40:55.231 --> 03:41:03.814
And that will end my three and a half hour tirade about, um, a paper that I am on the cover of nature for.

3996
03:41:04.254 --> 03:41:04.914
So, you know,

3997
03:41:06.173 --> 03:41:13.586
It's tough, but I don't really regret spending three and a half hours because this is kind of a dream come true.

3998
03:41:13.666 --> 03:41:14.288
It's monumental.

3999
03:41:14.308 --> 03:41:15.029
It's on the paper.

4000
03:41:15.129 --> 03:41:16.431
It's on the cover of Nature, dude.

4001
03:41:16.451 --> 03:41:16.612
Yeah.

4002
03:41:17.297 --> 03:41:39.923
even like the the you know i didn't write a single word of the paper but i was involved in the science and that's something that i think we can all be proud of all 250 of us that's a really big deal congratulations again thank you i i will just note for those who are tracking the information security on the project i've had no idea what krishna did for work for the longest time because it was classified

4003
03:41:40.922 --> 03:41:49.850
And that was so annoying, but I knew when the time would come, I would get to learn what it is you did because I knew you were so passionate about it and you were excited.

4004
03:41:49.870 --> 03:42:02.942
And to be able to sit through both parts of this and really understand at a real level kind of what it is you've been working on in the world you've been living in for so long and continue to do so.

4005
03:42:02.962 --> 03:42:03.882
Yeah.

4006
03:42:04.583 --> 03:42:05.824
It has just been such a blessing.

4007
03:42:06.124 --> 03:42:09.646
And just congratulations to our resident PhD.

4008
03:42:10.026 --> 03:42:15.070
We have already kept you all long enough, so I will not pontificate any longer.

4009
03:42:15.690 --> 03:42:17.051
If you can share a like, share a...

4010
03:42:17.071 --> 03:42:18.292
If you are still here...

4011
03:42:19.414 --> 03:42:21.535
And you're trying to listen to the song.

4012
03:42:21.575 --> 03:42:22.095
Let us know.

4013
03:42:22.175 --> 03:42:22.796
Let us know.

4014
03:42:22.876 --> 03:42:23.356
Seriously.

4015
03:42:23.396 --> 03:42:24.877
Just say, I'm still here.

4016
03:42:24.917 --> 03:42:26.897
That's going to be mind-blowing.

4017
03:42:27.098 --> 03:42:27.658
Anything.

4018
03:42:27.918 --> 03:42:29.479
This was meant to be two parts.

4019
03:42:29.679 --> 03:42:32.560
We didn't want to make it three parts, so we just said we're going to do it.

4020
03:42:33.000 --> 03:42:38.042
A like, a share, a comment, a five-star can really do a lot for us to get this podcast to more people.

4021
03:42:38.363 --> 03:42:40.864
We are the best science show on the planet.

4022
03:42:41.764 --> 03:42:45.766
People want us to make it shorter, but we can't because the science is just so good.

4023
03:42:46.426 --> 03:42:48.348
There's a lot of people who don't want to make it shorter.

4024
03:42:48.509 --> 03:42:48.889
There is.

4025
03:42:49.410 --> 03:42:53.675
And clearly, we're not.

4026
03:42:54.316 --> 03:43:02.285
As always, I am Lester Nari, joined by my co-host in our resident PhD and recent cover, story, co-author...

4027
03:43:02.922 --> 03:43:05.483
Krishna Chowdhury, our resident PhD.

4028
03:43:06.323 --> 03:43:10.784
If you are here this episode, you now really understand how quantum computing works.

4029
03:43:11.084 --> 03:43:12.544
What is the layout of the frontier?

4030
03:43:12.964 --> 03:43:14.204
I feel very educated.

4031
03:43:14.684 --> 03:43:19.245
I am now ready to allow my brain to decompress because that was some deep stuff.

4032
03:43:19.625 --> 03:43:29.387
We will see you all for a more chilled and relaxing and giving our resident PhD some time to decompress episode next week.

4033
03:43:33.469 --> 03:43:33.950
long.

4034
03:43:34.010 --> 03:43:35.052
It'll be a little bit more fun.

4035
03:43:35.092 --> 03:43:38.017
We're going to figure out what we're going to do, but this was really fantastic.

4036
03:43:38.037 --> 03:43:39.801
We'll see you all next week.

4037
03:43:41.148 --> 03:43:43.390
HRL research group, late night grind.

4038
03:43:43.790 --> 03:43:46.111
Lots of quantum dots, keep the layout fine.

4039
03:43:46.452 --> 03:43:48.893
Scaling it up while the losses stay low.

4040
03:43:49.233 --> 03:43:51.635
Prior quantum processing unit in the snow.

4041
03:43:52.035 --> 03:43:54.677
54 exchange, couple quantum dots in a row.

4042
03:43:54.717 --> 03:43:57.078
Tiny little pulses make the logic all flow.

4043
03:43:57.399 --> 03:43:59.120
Distance 5, repetition cold.

4044
03:43:59.140 --> 03:44:00.060
Lock it in tight.

4045
03:44:00.120 --> 03:44:01.802
Distance 2, error detecting.

4046
03:44:01.842 --> 03:44:02.862
Catch it mid-flight.

4047
03:44:02.882 --> 03:44:03.903
Superconducting with...

4048
03:44:08.227 --> 03:44:09.228
We'll be right back.

4049
03:44:35.932 --> 03:44:38.354
New result dropping from the fresh QPU.

4050
03:44:38.754 --> 03:44:41.096
Order of magnitude, different kind of view.

4051
03:44:41.396 --> 03:44:43.777
Lots of new developments humming in tune.

4052
03:44:43.878 --> 03:44:46.179
Automated tune up, calibrate the room.

4053
03:44:46.539 --> 03:44:48.861
Large valley splitting how they pull that off.

4054
03:44:49.241 --> 03:44:51.783
Tadis Lad leading while the numbers talk.

4055
03:44:52.003 --> 03:44:54.425
HL research group steady on the path.

4056
03:44:54.625 --> 03:44:57.207
Stacking every code in the low temp app.

4057
03:44:57.387 --> 03:44:58.968
Super conducting ribbon camp.

4058
03:45:01.855 --> 03:45:02.838
Kelvin Dream.

4059
03:45:02.919 --> 03:45:05.386
Low noise tunnel where the waveforms glide.

4060
03:45:05.667 --> 03:45:07.633
New kind of signal with the chill in the ride.

4061
03:45:07.653 --> 03:45:08.155
Strange only.

4062
03:45:45.798 --> 03:45:47.559
Transcription by CastingWords