Quantum error correction

41:37>> redundancy effectively. Okay. >> Where where several cubits are performing a computation >> and like loosely speaking you you you do you do like a voting type thing of like all of these different cubits are performing a computation and then you vote on what the actual thing is. That way if some if some people failed you can still have a a sense of what the algorithm actually is. Right? This is called error correction cuz there's going to be errors, but there's ways to mitigate for that error by um by assigning multiple physical cubits to a logical cubit. A [clears throat] logical cubit is your block sphere. That's the thing that the algorithm is operating on, right? And if you've got multiple

42:17physical cubits that are kind of keeping track of this information, >> um loosely speaking, >> you can you can form a redundancy. Now, it's it's it's a little bit trickier than that because there's 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. You're not really cloning information, but you're still keeping track of it on multiple physical cubits. Physical cubits meaning whatever your superconducting circuit, your trap ion, whatever. You got a multiple of these to create a single logical cubit. And the logical cubit is the thing that is doing the algorithm. And so there's almost that now in a system level case and I know maybe we're getting a little ahead of ourselves. We can come back. There's this idea that there are cubits that

42:58have different functional purposes. One might be tracking and one might be doing the the actual calculation. Yeah. >> And you can have some combination of these different types of cubits to get to a system 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. Exactly. And so cubits sort of take roles accordingly. >> Very good. Yeah. No, that's a really good analogy. >> Yeah. Um and so that's exactly right. And so when when we think about like you know noisy physical cubits versus >> the logical cubits that we're trying to emulate in this like logical space. Yeah. >> Um the only thing that really matters is fault tolerant

43:38>> quantum computing. Um, this is this is kind of a big thing these days, right? Which is, >> you know, suppose there's a like a bit flip error >> or there's a phase flip error where like it's on it's on it's on east, it's like 90° east and then whoop, all of a sudden it's like 90° west because I don't know, some random photon came in from from somewhere or there was like a some charge blah um bit flip air. It was in the north axis and then went to the south axis. No reason, right? >> Just quantum stuff. Yes, lot of stuff happening, right? Um in in if that happens, you better have these error correcting codes. These are this is a fancy way of saying that there's there's some um computational machinery that I

44:21can implement that is going to um keep track of the lost information and keep track of where I'm trying to go with the algorithm. And with that redundancy, I'm still able to compute whatever algorithm or circuit that I was trying to compute in the first place. Right? This is not like a no-go um deal breaker >> if if one of [snorts] these errors happens. >> Makes sense. There's the ability to detect and fix in post. We'll do it in post. >> Yeah, exactly. So, I better be able to do this very well, right? Because every single physical cubit is going to have these types of problems. And this is this idea of fault fault tolerant quantum computing. >> Yeah. So whenever you hear fault

45:01tolerant quantum computing the fault >> is this >> is these errors. >> It's either going north when it should be south or east when it should be west >> or Yeah. And it can be more complicated than this. Right. It could be like multiple cubits are doing weird things >> for sure. >> Right. Um to keep it simple. >> But to keep it simple, this is like one of the common ones, right? Yeah. It was north, now all of a sudden it's south. >> Fair enough. >> But if all of its neighbors are like, "Yo, you should we're all north." It's it's a combinatorial thing where it's like it [clears throat] because Yeah. So it is both at an individual level and then you have to zoom out to then how does that impact the system and so the complexity can get quite ridiculous. >> Exactly. Yeah. And one of the key things that matters with these types of um fall

45:42tolerant computing is what is the connectivity of your cubits. >> For example, like if you're only if if you're all on a line, >> I can only talk to the cubit behind me and in front of me, right? Um, if I'm in a square lattice, then I can talk to like four of my nearest neighbors, right? But if I'm all to all connected like some of the ones that we're going to um see claim, then I can talk to literally every single one somehow, right? And then and then my error code can be that much more efficient. So maybe I don't need that many physical cubits to encode a logical cubit, right? Because I've got larger quorum sensing in some sense. In um a side note, in biology we like biological systems do this all the time. Um, for example, when

46:25you're an embryo and like your cells are just a ball of of stem cells, right? But then each cell has to decide, I'm going to go be the head. I'm going to go be the tail. I'm going to go be a hand. I'm going to go be a liver cell. So on and so forth. How does the cell know where it is in the embryo? Right? How come I don't have a liver in my skull? >> Right. >> Right. How come a cell near my skull didn't decide I'm going to go be a liver? 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 they they start aggregating votes from their neighbors to try to

47:06bring that noise down and figure out okay so I'm I'm definitely liver right guys and then everyone around is like yeah cuz I'm going to be spleen I'm going to be stomach so you better be liver like like it's it's kind of cool that like like that's the kind of stuff that I used to study in a little undergrad project and Now you know the you know physics is connected even from biohysics to to quantum physics. >> This is why when you're playing on a squad with 11 players you have to communicate because the difference between a team that communicates and doesn't is players that are in their >> 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. And then >> yeah and we saw that live with Belgium versus USA. [laughter]

47:49We we will not talk about it. It was depressing. Um >> that was that was pretty bad. >> But but that's exactly what happened. >> But that's exactly what happened. And so this is actually very helpful because now now we're kind of setting the basis of like okay we now this criteria we talked about two points so far, right? We talked about cubit quality >> uh the ability to maintain itself and then cubit control over those like three stages, right? Right. The initialization, the actual computation and the measurement. Uh like how well are you able to control? >> Yeah. >> Even if you have good cubic quality, you can have bad cubit control. You can have good cubic control but bad cubic quality. >> Exactly. So you better be good at both. >> You better be good at both.

48:29>> And then that's leading us now >> to the final one to the final piece >> in our FFP criteria trademarking. [laughter] >> Um which is scalability and economics.