Quantum computers: amazing progress, but probably false supremacy claims • Hacker News Board

Re: Quantum computers: amazing progress, but probably false supremacy claims

#61

Post by GistNoesis » Sun, Oct 06, 2019, 1:42 PM UTC

chr1 wrote: post #58

GistNoesis wrote: post #53

Earlier quoted context omitted.

Quantum computing is a typical example of taking a model (QM), further than it was ever intended to. Instead of recognizing the fallacy, they blindly accept its promises : cramming an infinite computational power using very little mass. They then uses the excuse that it's extremely complicated to build to cover for the lack of results demonstrating the model is holding its promises. After a few decades, they will ach…

Is there a way to find how far a model stays valid other than taking it further than it was ever intended to? I personally like to think that physics can be explained by a discrete finite automaton so quantum computers are not possible, but believing this would be more stupid than believing the opposite. Whichever alternative is true, there is a good reason to try to build quantum computer, because the process itself…

If your model can't predict its limits, it is an indication that you are already past its limits.

When you build a model, you build it to map the range of behaviors you are interested in. When mathematical infinities of any kind (like infinite computational power) emerge it's usually a strong hint that the model is not applicable, not an invitation to fantasize about the things you will be able to achieve following your model outside of its region of trust.

You question your hypothesis and then look for an alternative model that is more probable. You don't spend your resources doubling down on blind model following.

Assuming some priors and Bayesian updating your beliefs about how the world works is probably a better strategy.

I am not a Physicist so I don't have skin in this game, but the QM scene really look like a mix between snake oil vendor and religion, and doing more of this "science" by marketing firms isn't really any scientist should wish for.

Re: Quantum computers: amazing progress, but probably false supremacy claims

#62

Post by [deleted] » Sun, Oct 06, 2019, 1:44 PM UTC

fsh wrote: post #44

undersuit wrote: post #11

My level of expertise on quantum computing is low. The announce of the imminent advent of the Quantum Computer seems to be recurring every few months these last few years because it's a moving target. HN recently featured an article about a supposed quantum-only algorithm being applied to normal computing. Algorithms are a vastly larger space to explore than general computing paradigms. Computer hardware is still adv…

To my knowledge D-wave has never demonstrated any useful application of their annealer. They have also never managed to show any "quantum advantage" where an algorithm on their machine scales better than the best known classical algorithm.

[deleted]

Re: Quantum computers: amazing progress, but probably false supremacy claims

#63

Post by rolltiide » Sun, Oct 06, 2019, 3:55 PM UTC

johncolanduoni wrote: post #52

rolltiide wrote: post #35

Am I understanding correctly that the whole idea is to get a bunch of qubits in one machine and then have them evaluate every possibility in a super dumb way but count on them to get the desired result faster than a transister based machine that knows what its looking for? And that we currently just can’t coordinate that many qubits at once and also cant keep them cool long enough to function?? This seems kind of rid…

This is not the case and is a constant frustration researchers have with how quantum computing is represented in the media. So much so that Scott Aaronson (who works on computational complexity theory, particularly as it relates to quantum computing) has a statement telling you that’s not the case in the heading of his blog: https://www.scottaaronson.com/blog/

I had to skim but that articles seems more of a gripe with “p-bits” being an even dumber concoction of standard computers

I didn't see how it dissected my understanding

edit: oh I see I had read the first post on that blog thinking it was what the attention was supposed to be on

Re: Quantum computers: amazing progress, but probably false supremacy claims

#64

Post by shroedingaway » Sun, Oct 06, 2019, 4:08 PM UTC

FartyMcFarter wrote: post #54

shroedingaway wrote: post #18

Earlier quoted context omitted.

No that's the funniest aspect of the Google result. They barely have any control over what their gates do. Gil makes this point, but doesn't call it out: they're claiming supremacy by turning the challenge around. "You can't classically simulate our device (which largely does it's own thing because of issues)." A kid shoots an arrow at a target. The arrow hits the haybale, but not the target. Suddenly the kid yells "…

> They barely have any control over what their gates do. I don't understand this, could you explain? My understanding is that the gates are perfectly normal quantum gates, which they use to connect qubits in a programmable way. Due to the probabilistic nature of quantum computing, running this circuit generates samples from a random distribution.

I attended a Google talk where they acknowledged difficulty in controlling their device. That was given as the motivation for running problems that consist of "random gates".

Re: Quantum computers: amazing progress, but probably false supremacy claims

#65

Post by FartyMcFarter » Sun, Oct 06, 2019, 4:46 PM UTC

shroedingaway wrote: post #64

FartyMcFarter wrote: post #54

Earlier quoted context omitted.

> They barely have any control over what their gates do. I don't understand this, could you explain? My understanding is that the gates are perfectly normal quantum gates, which they use to connect qubits in a programmable way. Due to the probabilistic nature of quantum computing, running this circuit generates samples from a random distribution.

I attended a Google talk where they acknowledged difficulty in controlling their device. That was given as the motivation for running problems that consist of "random gates".

My understanding from reading Scott Aaronson's FAQ is that the "random" in "random gates" just means that they pick a random circuit to evaluate. But this circuit is known, just like a program can pick a random number and then print it out.

The fact that quantum computing behaves "randomly" by nature further complicates the discussion :)

Re: Quantum computers: amazing progress, but probably false supremacy claims

#66

Post by fhars » Sun, Oct 06, 2019, 5:25 PM UTC

rolltiide wrote: post #63

johncolanduoni wrote: post #52

Earlier quoted context omitted.

This is not the case and is a constant frustration researchers have with how quantum computing is represented in the media. So much so that Scott Aaronson (who works on computational complexity theory, particularly as it relates to quantum computing) has a statement telling you that’s not the case in the heading of his blog: https://www.scottaaronson.com/blog/

I had to skim but that articles seems more of a gripe with “p-bits” being an even dumber concoction of standard computers I didn't see how it dissected my understanding edit: oh I see I had read the first post on that blog thinking it was what the attention was supposed to be on

The link was not to the article, as the post you replied to clearly stated.

Re: Quantum computers: amazing progress, but probably false supremacy claims

#67

Post by lawrenceyan » Sun, Oct 06, 2019, 5:27 PM UTC

computerex wrote: post #59

lawrenceyan wrote: post #48

Earlier quoted context omitted.

We can look directly to the paper itself to see how it addresses the issues of error uncertainty that the author premises his blogpost around: “This fidelity should be resolvable with a few million measurements, since the uncertainty on FXEB is 1/√Ns, where Ns is the number of samples. Our model assumes that entangling larger and larger systems does not introduce additional error sources beyond the errors we measure…

> We can look directly to the paper itself to see how it addresses the issues of error uncertainty that the author premises his blogpost around Can you demonstrate how the author "premises his blogpost around" the "issues of error uncertainty"? I don't think that was the main premise of the paper, at all.

I’m unsure of what you’re trying to say here. The issues that Kalai poses as to the validity of the experiments done by Google’s Quantum AI Lab is that the difference between the ideal distribution D and sampled distribution D’ is meaningfully different enough from each other, that significant results cannot be obtained from the experiment in comparing performance to classical simulations.

The excerpt I posted above from the actual paper directly addresses the points made by Kalai, and provides reasoning and analysis for determining the 5 sigma confidence of their results.

This is again, why in my original post, I said I believed Kalai to be nitpicking, primarily because the additional statistical testing he proposed should be done, while surely never a bad thing wouldn’t do anything to change the ultimate confidence determinations and results. Kalai of course believes that the testing was insufficient. The easiest thing to do resolve such an issue is to perform the additional work that Kalai asks for in order to appease his suspicions. I have personally no problem with that. It’s never a bad thing to do more tests.

Re: Quantum computers: amazing progress, but probably false supremacy claims

#68

Post by computerex » Sun, Oct 06, 2019, 9:47 PM UTC

lawrenceyan wrote: post #67

computerex wrote: post #59

Earlier quoted context omitted.

> We can look directly to the paper itself to see how it addresses the issues of error uncertainty that the author premises his blogpost around Can you demonstrate how the author "premises his blogpost around" the "issues of error uncertainty"? I don't think that was the main premise of the paper, at all.

I’m unsure of what you’re trying to say here. The issues that Kalai poses as to the validity of the experiments done by Google’s Quantum AI Lab is that the difference between the ideal distribution D and sampled distribution D’ is meaningfully different enough from each other, that significant results cannot be obtained from the experiment in comparing performance to classical simulations. The excerpt I posted above…

I think you have serious conceptual holes in your understanding of the post.

> The issues that Kalai poses as to the validity of the experiments done by Google’s Quantum AI Lab is that the difference between the ideal distribution D and sampled distribution D’ is meaningfully different enough from each other, that significant results cannot be obtained from the experiment in comparing performance to classical simulations.

This is categorically false. Can you quote the passage(s) that lead you to this conclusion?

Re: Quantum computers: amazing progress, but probably false supremacy claims

#69

Post by lawrenceyan » Sun, Oct 06, 2019, 11:52 PM UTC

computerex wrote: post #68

lawrenceyan wrote: post #67

Earlier quoted context omitted.

I’m unsure of what you’re trying to say here. The issues that Kalai poses as to the validity of the experiments done by Google’s Quantum AI Lab is that the difference between the ideal distribution D and sampled distribution D’ is meaningfully different enough from each other, that significant results cannot be obtained from the experiment in comparing performance to classical simulations. The excerpt I posted above…

I think you have serious conceptual holes in your understanding of the post. > The issues that Kalai poses as to the validity of the experiments done by Google’s Quantum AI Lab is that the difference between the ideal distribution D and sampled distribution D’ is meaningfully different enough from each other, that significant results cannot be obtained from the experiment in comparing performance to classical simulat…

> By creating a 0-1 distribution we mean sampling sufficiently many times from that distribution D so it allows us to show that the sampled distribution is close enough to D. Because of the imperfection (noise) of qubits and gates (and perhaps some additional sources of noise) we actually do not sample from D but from another distribution D’. However if D’ is close enough to D, the conclusion that classical computers cannot efficiently sample according to D’ is plausible.

Re: Quantum computers: amazing progress, but probably false supremacy claims

#70

Post by chr1 » Mon, Oct 07, 2019, 5:32 AM UTC

GistNoesis wrote: post #61

chr1 wrote: post #58

Earlier quoted context omitted.

Is there a way to find how far a model stays valid other than taking it further than it was ever intended to? I personally like to think that physics can be explained by a discrete finite automaton so quantum computers are not possible, but believing this would be more stupid than believing the opposite. Whichever alternative is true, there is a good reason to try to build quantum computer, because the process itself…

If your model can't predict its limits, it is an indication that you are already past its limits. When you build a model, you build it to map the range of behaviors you are interested in. When mathematical infinities of any kind (like infinite computational power) emerge it's usually a strong hint that the model is not applicable, not an invitation to fantasize about the things you will be able to achieve following y…

All the physical theories we had so far require infinite computational power, because they work with real numbers, it's easy to say that it is wrong, but that's not really useful without saying what is right.

There are several interpretations of quantum mechanics that predict quantum computers not working in different ways, to find which one of them is correct you need an experiment that is not described by traditional view. Building quantum computers is the first experiment that has a chance to show what exactly is wrong with QM. Even the people who think there is nothing wrong with QM agree that quantum computer not working would be a bigger discovery than working, and are considering all the alternatives, so i don't see how it is anything like a religion.