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Scott’s Supreme Quantum Supremacy FAQ

scottaaronson.com

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Re: Scott’s Supreme Quantum Supremacy FAQ

#61

Post by itcrowd »

bjornsing wrote: post #56
bjornsing wrote: post #45

I have the greatest respect for Scott, but I do think he’s being a bit too enthusiastic here in comparison with the D-wave. At the very least I think he should have included this question in his list: Q: Why can the D-wave not be used to illustrate “quantum supremacy” in a similar way? (As I understand it the D-wave can sample from the solutions to ”ising model-like” problems, which I assume would be extremely diffic…

Another reason I feel this is oversold: This quantum “computer” cannot run Shores factorization algorithm. But if it could it would only be able to factor integers up to 2^53. The time required to factor a 2^60 to 2^80 integer on a classical computer is measured in milliseconds [1]... Quantum supremacy in any reasonable sense of the word supremacy is a long way off. 1. https://hal.inria.fr/file/index/docid/451604/fil…

You may not agree with the authors' or Aaronsons' definition of quantum supremacy, that's ok. I think his definition is very reasonable. Aaronson argues that this experiment will prove quantum computing supremacy in great length and defined it in the first entry of the FAQ as follows:

> [quantum computing supremacy] term refers to the use of a quantum computer to solve some well-defined set of problems that would take orders of magnitude longer to solve with any currently known algorithms running on existing classical computers

.. and continues to explain why this setup does exactly that.

Re: Scott’s Supreme Quantum Supremacy FAQ

#62

Post by bjornsing »

sanxiyn wrote: post #60
bjornsing wrote: post #45

I have the greatest respect for Scott, but I do think he’s being a bit too enthusiastic here in comparison with the D-wave. At the very least I think he should have included this question in his list: Q: Why can the D-wave not be used to illustrate “quantum supremacy” in a similar way? (As I understand it the D-wave can sample from the solutions to ”ising model-like” problems, which I assume would be extremely diffic…

In principle, there is no reason why D-wave also can't achieve quantum supremacy. It is just that D-wave hasn't, so far. As for Ising model, D-wave didn't outperform classical algorithm after classical algorithm was tuned (it was a new problem, so existing classical algorithm wasn't the best possible), see https://arxiv.org/abs/1401.1084 , also there are reasons to suspect why Ising model will not provide any quantum…

Well D-wave is evaluated on an optimization task. This Google thing isn’t even trying to solve a real problem. What says you can’t get some very hard to replicate random bits out of a D-wave?

Re: Scott’s Supreme Quantum Supremacy FAQ

#63

Post by sanxiyn »

bjornsing wrote: post #62
sanxiyn wrote: post #60

Earlier quoted context omitted.

In principle, there is no reason why D-wave also can't achieve quantum supremacy. It is just that D-wave hasn't, so far. As for Ising model, D-wave didn't outperform classical algorithm after classical algorithm was tuned (it was a new problem, so existing classical algorithm wasn't the best possible), see https://arxiv.org/abs/1401.1084 , also there are reasons to suspect why Ising model will not provide any quantum…

Well D-wave is evaluated on an optimization task. This Google thing isn’t even trying to solve a real problem. What says you can’t get some very hard to replicate random bits out of a D-wave?

Do you retract the claim Ising model problems are "extremely difficult" for classical computers? I replied with practical and theoretical considerations why it is not so.

Re: Scott’s Supreme Quantum Supremacy FAQ

#64

Post by quickthrower2 »

SpicyLemonZest wrote: post #28
codeulike wrote: post #27

Earlier quoted context omitted.

Google's device is not encoding complex computational problems. Its just being told to arrange its qbits into a random series of gates. Could it do the Fizz Buzz algorithm? Or output the Fibonacci sequence? If not, then in what way is it programmable?

What's a classical computer, if not silicon arranged into a random series of gates? I'm not sure how to evaluate the question of whether it could do the Fizz Buzz algorithm. Could it run fizzbuzz.c? No, it doesn't have an OS. Could it perform a sequence of operations isomorphic to "count to 100 by 3s and 5s"? It sounds like Aaronson's answer would be yes, but I think you'll be skeptical (and I am too) about whether t…

A stone tablet could "perform" a sequence of operations isomorphic to "count to 100 by 3s and 5s". But "count to N by 3s and 5s" for any N : 0 < N < 2^32. Well that'd require a lot of stone.

Re: Scott’s Supreme Quantum Supremacy FAQ

#65

Post by tagrun »

itcrowd wrote: post #55
tagrun wrote: post #43

Earlier quoted context omitted.

We do want the chip to be "large" eventually. The scalability doesn't have anything with those, however. Refrigerators are pretty large and these devices are really really tiny; also qubits shouldn't be spaced "far" apart, this would kill all the (controllable) couplings.

I was a little too fast and loose in my previous post. You are correct that we want a large [number of qubits] on a chip eventually. The chips are tiny and the fridges large enough for now (50 qubits). It's not clear to me that they can handle thousands of qubits as imagined. The cryostat will undoubtedly be able to house the chip, but the extra electronics / cables must run in there as well. With 1000 qubits and 2 c…

There is a scalability problem but due to different reasons. See my other comment in this thread for details.

Classical circuitry is an issue, but not as much as you think. What happened is Martinis' group and others moved forward with a quick & dirty design which worked well for their device but can't be scaled (they basically didn't have the expertise like silicon people had). Nevertheless, it's not a fundamental problem, the circuitry for silicon based spin qubits never had this problem for example and xmons won't either, they just keep reiterating as the number of qubits increase, it's the least of their worries regarding scalability. There are far bigger problems regarding the scalability.

Re: Scott’s Supreme Quantum Supremacy FAQ

#66

Post by sanxiyn »

bjornsing wrote: post #53
rsln-s wrote: post #47

Earlier quoted context omitted.

Unfortunately, the same complexity considerations do not hold for Ising problems. While many NP-hard problems can be formulated in Ising form, it is often not hard to get a “pretty good” solutions to these problems. DWave and collaborators have spent a decade trying to come up with exactly the same thing as demonstrated here — namely, a problem specifically designed to demonstrate quantum advantage of any sort — and…

I’m aware of D-wave’s struggles, but my impression was that they had failed at finding a “deterministic” problem where they could show quantum advantage. I’ve never heard a claim that whatever probability distribution the D-wave can sample from a classical computer can also sample from. I’d love to read about it if you have a reference!

My understanding is that it is exactly the case D-wave probability distributions can be sampled classically.

Re: Scott’s Supreme Quantum Supremacy FAQ

#67

Post by bjornsing »

itcrowd wrote: post #61
bjornsing wrote: post #56

Earlier quoted context omitted.

Another reason I feel this is oversold: This quantum “computer” cannot run Shores factorization algorithm. But if it could it would only be able to factor integers up to 2^53. The time required to factor a 2^60 to 2^80 integer on a classical computer is measured in milliseconds [1]... Quantum supremacy in any reasonable sense of the word supremacy is a long way off. 1. https://hal.inria.fr/file/index/docid/451604/fil…

You may not agree with the authors' or Aaronsons' definition of quantum supremacy, that's ok. I think his definition is very reasonable. Aaronson argues that this experiment will prove quantum computing supremacy in great length and defined it in the first entry of the FAQ as follows: > [quantum computing supremacy] term refers to the use of a quantum computer to solve some well-defined set of problems that would tak…

Yea... I’m not suggesting of course that Scott is wrong about this being an illustration of “quantum supremacy”... (Did you think I was...?)

But comparing it to manned flight or the first nuclear reactor... In those two cases there was a clear path to something very useful. I’m my mind this experiment changes very little as to how probable it is that we will soon have useful quantum computers, or even that we will ever have them. I guess that’s another question for Scott’s list:

Q: If what we care about is computing solutions to difficult real world problems, in what way is this a meaningful milestone?

Re: Scott’s Supreme Quantum Supremacy FAQ

#68

Post by calhoun137 »

dcposch wrote: post #59
calhoun137 wrote: post #49

I think we need to comes to grips with a hard truth about the reality of academic life. Once you invest decades of your life into a research subject, if it turns out the entire thing is never going to work, there are major social and financial pressures to deceive the public about the true nature of the subject. I saw this happen with string theory first hand, and my experience with string theory was a major factor t…

> Once you invest decades of your life into a research subject, if it turns out the entire thing is never going to work, there are major social and financial pressures to deceive the public about the true nature of the subject. You're implying that Scott Aaronson is being deceptive. I think that needs better evidence. The story you linked to is two years old and it's about QC skeptic Gil Kalai. Scott addresses him di…

I am not very familiar with Scott Aaronson and am just making a general observation about the subject of QC, I have no idea what his motivations or intentions are. If Scott believes QC will day be practical and I don't, only time can tell who is right and who is wrong. I have seen this kind of goal post moving in string theory, and its been going on for 20 years with QC in a strikingly similar way imo.

There is no way to argue against this kind of goal post moving style of debate because even if another 20 years go by and QC still don't exist on a practical level, the goal posts will just keep getting moved.

I am extremely confident that this will continue until the public gets bored of hearing about it.

Re: Scott’s Supreme Quantum Supremacy FAQ

#69

Post by sanxiyn »

gowld wrote: post #58
whatshisface wrote: post #4

If it goes well, the history of quantum computing will be divided up in to three eras: the era of twisty philosophical arguments that it's working ("the molecule is simulating itself"), the era of academic arguments that it's working ("we can solve this one carefully constructed problem") and the era of practical arguments ("Amazon is selling QC time for $20/kilogate-bit, what do you mean it's not possible?"). Quantu…

What are the theoretical models for the energy cost of computing on a qubit? I'll be excited for QC when there is known way (even with some handwaving and future-tech plans) to compute a non-trivial result for a reasonable sum, such as "crack someone's private RSA key for under $10M of compute cost"

This depends on your definition of "trivial". But if we restrict it to factoring, no, there is no known path to QC factoring at the moment, none at all.

Re: Scott’s Supreme Quantum Supremacy FAQ

#70

Post by krastanov »

daxfohl wrote: post #52

What's e.g. China and Russia doing in this space? Or the US Gov't for that matter? I can't imagine that national governments are just waiting for Google and IBM to do the research and publish their results. Is it possible/likely that NSA or some other national equivalent is way beyond these results already?

There are a lot of research teams working on this in China/Europe/North America/Australia (present at most big conferences in the field). Not much in Russia from what I have seen (not counting well known Russian scientists that work in other countries).
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