Google claims to have proved its supremacy with new quantum computer • Hacker News Board

Re: Google claims to have proved its supremacy with new quantum computer

#151

Post by superposeur » Mon, Jul 03, 2023, 9:22 PM UTC

Do you know if there are any arguments in the literature to the effect that actually useful quantum supremacy may never be possible in principle (not merely in practice)?

What I mean is: decoherence with environment must be held at bay long enough for the final answer to appear in the qubits with high probability. Based on examples from thermodynamics (such as impossibility of extracting useful work from a heat reservoir without a second, lower-temperature reservoir into which to dump heat), I could imagine a scenario where decoherence would always foil the computation at some point, perhaps at some intermediate time or in the final measurement. In particular examples, this would show up as irksome experimental limitations, but in fact these limitations would all stem from a deeper prohibition. And to the extent that decoherence could be managed (such as in the cited experiment), the resulting computation would not be "useful".

Re: Google claims to have proved its supremacy with new quantum computer

#152

Post by __MatrixMan__ » Mon, Jul 03, 2023, 9:29 PM UTC

ori_b wrote: post #98

robot_no_421 wrote: post #88

Earlier quoted context omitted.

You're not modeling or predicting anything though. That's like saying "what if I built a bridge that failed on the first day? A computer would need several days to calculate all the forces that led to the failure, but my bridge failed just fine without any computer help". Well... yes. But try building a bridge that doesn't break. Or to keep with your scenario, try to predict exactly where and how your stick will brea…

Does Google's implementation of quantum computing help with this sort of scenario, or is it a really fancy way of breaking the bridge?

Well you don't have to sacrifice any sticks or bridges to see what happens, so that's a plus.

One could imagine stimulating experiments that are implausible to actually perform.

Re: Google claims to have proved its supremacy with new quantum computer

#153

Post by dekhn » Mon, Jul 03, 2023, 9:29 PM UTC

the best thing about watching the entire quantum computing debacle is every time somebody says their QC does something faster than a classical computer, somebody tunes the classical computer to beat the QC. Combined with the fact that chip infrastructure is already paid for and there is a large market to enable economy of scale, coupled with the lack of true problems where exponentially better problem solving is critical to business or military success, means we're going to see a series of QC claims that really just prop up classical computers for some time.

(I used to work in supercomputing and chemistry and await the day we have useful QCs doing simulation better than what we can do on supercomputers)

Re: Google claims to have proved its supremacy with new quantum computer

#154

Post by nier » Mon, Jul 03, 2023, 9:29 PM UTC

refulgentis wrote: post #144

lbourdages wrote: post #141

Earlier quoted context omitted.

Do you have a link handy? You've piqued my curiosity!

Here's an exhaustive covering: https://www.scottaaronson.com/democritus/lec14.html I would have picked it up in bits and pieces from blogs over years, here's an attempt to render that useful that is surely nitpickable: TL;DR: there's two types of caring about Google's claims of quantum supremacy: 1. HN tends to assume these articles are about breakthrough in _product usefulness_ and then tsk tsk about lack of impact.…

From the article linked by parent:

«To summarize, I think that arguing with skeptics is not only amusing but extremely useful. It could be that quantum computing is impossible for some fundamental reason. So far, though, I haven't seen an argument that's engaged me in a really nontrivial way.»

«Very little of what we do in theoretical computer science is directly connected to a practical application. That's just not what we're trying to do. Of course, what we do has applications, but indirectly. We're trying to understand computation. If you take that as our goal, then it seems clear that starting from the best physical theories we have is a valuable activity. If you want to ask a different question, such as what we can do in the next five to ten years, then, that's fine. Just make it clear that's what you're doing.»

Re: Google claims to have proved its supremacy with new quantum computer

#155

Post by shawabawa3 » Mon, Jul 03, 2023, 9:30 PM UTC

deepburner wrote: post #137

Quantum Computing/Information researcher here. This article is largely garbage, the original (~2 month old) paper is surprisingly readable [0] and I suggest you to check it out. Here's my $0.02: The efforts of the Google team is commendable in that they're trying to squeeze as much out of their noisy systems as possible until error correction is here (they need to, to justify their existence after all) and they are a…

> Maybe someone can tell me what fast prime factorization is good for besides breaking encryption.

Maybe someone can tell me what alchemy is good for besides turning lead into gold?

Re: Google claims to have proved its supremacy with new quantum computer

#156

Post by chaboud » Mon, Jul 03, 2023, 9:33 PM UTC

riwsky wrote: post #140

gnramires wrote: post #135

Earlier quoted context omitted.

I think you can make the case that, for example, going out, taking a stick from a forest, breaking it and record the sound will be much more economical than trying to simulate a realistic stick breaking sound -- in particular in developer time trying to model sticks and wood breaking sounds in a convincing way (suppose we need say an art asset for a game). It's something complexity theory isn't well prepared to tackl…

Complexity theory doesn’t handle it, but that’s why I didn’t use complexity theory. Economics handles it fine: no one’s ever paid you or anyone else to do a wood-breaking simulation at a sufficient physical level of detail to capture the sound accurately, so the comparative savings on it aren’t economically valuable.

Sound effect libraries have long included the sounds of wood breaking/cracking, generally recorded (rather than simulated). A couple of jobs ago, we sold sound effect libraries that cost 2-5x the cost of the software applications that they were used with (hundreds to thousands of dollars).

I think you’d be hard pressed to find economists (beyond freshman college students who recently discovered Nietzsche second hand at a party) arguing for a purely direct monetary expression of value, but even they would have to admit that recordings of broken sticks in snow covered forests have non-zero value.

Re: Google claims to have proved its supremacy with new quantum computer

#157

Post by gnramires » Mon, Jul 03, 2023, 9:36 PM UTC

riwsky wrote: post #140

gnramires wrote: post #135

Earlier quoted context omitted.

I think you can make the case that, for example, going out, taking a stick from a forest, breaking it and record the sound will be much more economical than trying to simulate a realistic stick breaking sound -- in particular in developer time trying to model sticks and wood breaking sounds in a convincing way (suppose we need say an art asset for a game). It's something complexity theory isn't well prepared to tackl…

Complexity theory doesn’t handle it, but that’s why I didn’t use complexity theory. Economics handles it fine: no one’s ever paid you or anyone else to do a wood-breaking simulation at a sufficient physical level of detail to capture the sound accurately, so the comparative savings on it aren’t economically valuable.

Indeed, not a disagreement, just a contribution to the commentary :)

Re: Google claims to have proved its supremacy with new quantum computer

#158

Post by zerodensity » Mon, Jul 03, 2023, 9:38 PM UTC

deepburner wrote: post #137

Quantum Computing/Information researcher here. This article is largely garbage, the original (~2 month old) paper is surprisingly readable [0] and I suggest you to check it out. Here's my $0.02: The efforts of the Google team is commendable in that they're trying to squeeze as much out of their noisy systems as possible until error correction is here (they need to, to justify their existence after all) and they are a…

Questing regarding error correction and logical qbits. From my very limited understanding logical qbits could mitigate some of the error but uses multiple physical qbits for every logical qbits. Has anyone created a quantum computer that has logical qbits? Say a small one with 16 physical 4 logical qbits quantum computer, or similar.

Re: Google claims to have proved its supremacy with new quantum computer

#159

Post by chaboud » Mon, Jul 03, 2023, 9:39 PM UTC

jcims wrote: post #66

dataflow wrote: post #7

Dumb question: Say I have a wooden stick and I break it in half in less than a second. Assume a computer would need several minutes to simulate everything that would've happened in the stick. I clearly got the output faster than a computer (and with more precision), so does this imply I'm doing anything particularly fascinating? I assume the same scenario is possible to concoct for a quantum computer. I assume it wou…

I wonder about that frequently. The universe 'executes' physics in, as far as I can tell, a realtime basis (at least within the local reference frame). What is that called as compared to computing a model of the same.

Why do you think time dilation needs to occur in our simulation? Be it from instance-shard transition due to cell crossing (special relativity) or inter-node lag due to spatial density (general relativity), system design constraints dictated the very rules of our “physical” existence.

(Poe’s Law notice: yes, I’m joking)

Re: Google claims to have proved its supremacy with new quantum computer

#160

Post by dekhn » Mon, Jul 03, 2023, 9:40 PM UTC

refulgentis wrote: post #134

lbourdages wrote: post #49

Earlier quoted context omitted.

The main issue I had with their demonstrations were that the problems they chose were essentially "let's show that a quantum computer is better at being a quantum computer than a classical computer". Obviously they are, just like I'm better at being a human than ChatGPT is. I'm not saying they suck, but to proclaim that "quantum computers are superior" you need an actual use-case, IMO.

It's absolutely non-obvious, I'm dead serious. As far as I've understood keeping up over the years, there's a credible argument from a respected academic in the QC community that quantum computing is impossible.

it's not impossible (from a theoretical, and possibly physical perspective) but it's likely that there are no problems which would motivate the necessary investment to demonstrate a QC doing something useful which we couldn't also do in reasonable time on a classical supercomputer.

Kind of like fusors: sure, you can do nuclear fusion in your garage but you're putting in far more energy than you are generating.