The superconducting wiring problem

1:19:21might not have to >> might not have to. Right. Um, so finally, let's get into the scalability in electronics. >> Yep, there's a wiring problem. This is the Google Willow computer. All of those lines that you're seeing, those are coaxial cables that bring the microwaves down to the cubit. Okay, that's not the refrigeration. The refrigeration is mostly in the metal. All of those lines are microwave lines. >> Oh, that's interesting. >> Okay. Okay. >> That's the microwaves that are talking to your cubits. Yeah. Yeah. >> Um and a lot of these lines are fat. They're semi- rigid coaxial cables um made out of like stainless steel or like um superconducting nobbium. And they

1:20:02deliver some resonant frequency to these individual cubits. And this is the stuff that goes all the way down to the cubits. 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. >> Yeah. >> Okay. Um >> and we live in a wireless world. No, I'm kidding. [laughter] >> Effectively now the other the other problem is um the cubid itself is at tens of millichelvin. >> Oh yeah. >> Right now if and this is what a dilution refrigerator looks like. A dilution refrigerator you can think of as a Russian nesting doll of uh big and then and then you use the big as a heat dump for

1:20:42>> at the top >> at the top. At the top you have like a 55 Kelvin, right? I mean at the top I guess you have room temperature. That's where the heat is getting dumped. Um, you use the room temperature to dump heat and get down to 55 Kelvin. And then you use another stage to get down to 4 Kelvin to dump heat to the 55 Kelvin which dumps heat up back to room. So you have this Russian nesting doll of like cooling stages, right? All the way down at the very end is the 10 ml stage which is where your cubits sit. But all of your control lines, the microwaves and everything have to go all the way down to 10 millichelvin in order to talk to your cubits. That means you're heating up that 10 millichelvin stage

1:21:23>> with your microwave >> with a bunch of microwaves. >> Yeah. And there was a lot of them. >> And there was a lot of them. So the question is like how many how many can I can I get in this? >> There there's some limiting capacity based on the need to be able to control the levels of heat at some very very low level. Yes. And so there's some like upper limit theoretically. Exactly. >> Like how many microwave lines can you actually put there before it becomes >> 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 transmons that you saw earlier, they're at the scale of a millter. >> 1 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

1:22:04going to fit in a single dilution refrigerator. >> Okay. So, one of So, there's there's there's a bunch of problems here. Um, the cubid itself is too big. There's too many wires that are going down. Um, and there's a frequency crowding, right? For a single sort of chip, there's not that many that I can do mathematically even. Um so in each dilution refrigerator, I can't actually fit that many cubits. What I'd have to do is get a bunch of dilution refrigerators and rig them up. >> It's kind of like a server rack where you have multiple individual servers into this rack system. >> Exactly. And um actually IBM is kind of

1:22:46working on that. >> Okay. >> They've made a modular dilution refrigerator. This came out very very recently. >> Okay. um where they're showing that you can take a bunch of single dilution refrigerators, fit 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 way pave way for fall tolerant quantum computing because you've got a bunch of these. You connect them together. Now the communication between one dilution refrigerator and the next better be very very good. >> That's another layer. That's another layer that I have to worry about >> because now you're creating this uh multi like this in individual component now in a larger system that was already its own system. >> Mhm. Yeah. And and effectively if I rig

1:23:27a bunch of these dilution refrigerators up, I'm going to need like a data center type of warehouse. >> Yeah. Yeah. >> With a bunch of dilution refrigerators all rigged up. >> Yeah. And we already can't get data centers. >> Right. We already hate data centers. >> Right. Right. And we're using that as a as a as a structure an architectural and structural point. It's not literally a data center. >> No. Um it's a quantum I guess it's a quantum I don't know if you >> but the point is you're talking about the scale and the size of power, water, physical space that's necessary to actually have this >> helium 3. Where you going to get the helium 3? I will say it looks really nice. It does. >> The marketing photo looks great, >> right? And like ju just for one of these

1:24:08there's going to be a lot of helium 3. 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 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 cubits um for a thousand plus logical cubits, >> which is not the million we talked about earlier. >> No, it's just a thousand >> thousand logical cubits, you need 10 million physical cubits of these transponds. And um you need like 10 million dollars, right? For a million, you you you're talking like billions of dollars for a single quantum computer. >> Yeah. >> Yeah. That's tough. >> It's tough. It's tough. Billions of

1:24:49dollars for a single computer. >> It's not going to that's not right. And the footprint is the size of a warehouse. Um Yeah. So, let's let's look at the final verdict. >> Final verdict. >> The FP criteria for superconducting circuits. Cubid quality I'm going to say is 5 out of 10. Cubit control is 5 out of 10. scalability in economics 1 out of 10 for a total of 11 out of 30. Um the quantitative criteria about which we judge this is of course propri proprietary this prop proprietary FFP uh IP um if you claim that I made these numbers up uh I will sue you. I guess [laughter] that's that's what uh >> you are making claims against our

1:25:30proprietary uh trade secrets. >> Yeah. Yeah. Yeah. if you if you claim that I mean you you'll see how these numbers get when we go to 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 this whole point we talked about earlier about uh electric relays and vacuum tubes yes they could operate as transistors however uh if you want an iPhone you cannot have an iPhone made of vacuum tubes And ultimately what is going to matter in these spaces because of the way we engage with technology in general and

1:26:12the use cases for how people want to use this stuff 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. But then 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 we have to commit to this is so we have to make we have to like >> make the economics fit >> into this path we've already spent billions of dollars on and this is where you get a lot of the tension in these corporate environments of like well we can't like pivot. >> Yeah. And it like to be clear, I mean, we're not trying to make an iPhone out of quantum computers, but we're trying

1:26:53to have a lot of quantum computers. And if a single quantum computer is billions of dollars, that's not great. >> We we Where's the Helium 3 going to come from? >> Yeah. Yeah. Yeah. Yeah. Exactly. >> I mean, there's like there's like functional >> Yeah. >> Even if you just had one. >> Yeah. And like you can't make this in a in a TSMC, for example, right? And things like that. >> So, okay. that that was that was >> like it's it's it's been great for the quantum computing industry because it's been able to get to like this um intermediate scale quantum computer where they can show quantum supremacy and things like that. I just don't think it's the future. >> That's fair. Superconducting cubits 11 out of 30.