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IBM casts doubt on Google's claims of quantum supremacy

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Re: IBM casts doubt on Google's claims of quantum supremacy

#41

Post by Symmetry »

akjssdk wrote: post #8

The main takeaway here is figure 1 in this article: they show that for an increasing circuit depth, computation time (on a classical computer) scales linearly. Google claims, on the other hand, that a classical calculation would scale exponentially. This is the basis for the graph in the Google blog [1], which seems to suggest that the Quantum computer can easily reach points (such as qbits=50, cycles=25) which the c…

There are many problems where the best known quantum algorithm is asymptotically better than the best known classical algorithm but, as far as I've heard, nobody has ever found a case where the best quantum algorithm can be proved to be better than the best classical algorithm. So there's always going to be a danger of this happening no matter what problem you attack.

Re: IBM casts doubt on Google's claims of quantum supremacy

#42

Post by anonymousab »

JohnJamesRambo wrote: post #20
nautilus12 wrote: post #6

Saying that it evokes "white supremecy" is kind of a pathetic move.

Well the word creeps me out and I wish they would choose another. It isn’t even the right word to use since the intended meaning is a quantum computer that can do something that a classic computer can’t do at all, not just better at it. Quantum Possible sounds better to me.

> a quantum computer that can do something that a classic computer can’t do at all, not just better at it.

When speed is an aspect of the requirement, then it's something the other computer can't do.

E.g. 'complete this calculation in n days on hardware x' or 'completed this calculation with time complexity t and memory complexity m'

Re: IBM casts doubt on Google's claims of quantum supremacy

#43

Post by hktuotroi »

Symmetry wrote: post #41
akjssdk wrote: post #8

The main takeaway here is figure 1 in this article: they show that for an increasing circuit depth, computation time (on a classical computer) scales linearly. Google claims, on the other hand, that a classical calculation would scale exponentially. This is the basis for the graph in the Google blog [1], which seems to suggest that the Quantum computer can easily reach points (such as qbits=50, cycles=25) which the c…

There are many problems where the best known quantum algorithm is asymptotically better than the best known classical algorithm but, as far as I've heard, nobody has ever found a case where the best quantum algorithm can be proved to be better than the best classical algorithm. So there's always going to be a danger of this happening no matter what problem you attack.

Isn't quantum factoring proven to be exponentially faster than the best known classical one?

The only question is we don't know if there is a better classical factoring algorithm.

Wikipedia:

> On a quantum computer, to factor an integer N, Shor's algorithm runs in polynomial time. This is almost exponentially faster than the most efficient known classical factoring algorithm, the general number field sieve, which works in sub-exponential time

Re: IBM casts doubt on Google's claims of quantum supremacy

#44

Post by poelzi »

I know they don't understand λ_spm, I know their quantum orbit is totally fucked up. I know that they don't understand short magnetic field condition. I know their particle sizes are all off. (Reason you can' unify QM and GR btw). They are lacking the relativistic micro-curviture sourrounding the nucleus. I know they don't understand superconductor correctly, thats why the fractional quantum hall effect is a mystery. Superposition does not mean what they think (over interpretation).

Most of the ideas about Quantum-Computers can never be done. You can run certain optimizations when you can model some applications as energy states, but very limited spectrum of applications.

Re: IBM casts doubt on Google's claims of quantum supremacy

#45

Post by mannykannot »

mellosouls wrote: post #21

Repeating my question from the other thread: If IBM can cast doubt by describing a 2.5 day classical run, why not just do that instead, and blow the claim out of the water? There were a couple of responses (thanks) but I still don't understand - it looks like it's not as easy as they imply.

Such a demonstration would prove nothing of importance, partly because the issue is not how fast a particular run takes, but how running time grows with the size of the problem. More significantly, the issue is whether the paper's argument for its original claim is sound, and that would be best addressed by showing where it goes wrong. For a brief and clear explanation, read this excellent post:

https://news.ycombinator.com/item?id=21334025

If you don't follow what is being said there, reposting your question will not help.

Re: IBM casts doubt on Google's claims of quantum supremacy

#46

Post by missosoup »

hktuotroi wrote: post #43
Symmetry wrote: post #41

Earlier quoted context omitted.

There are many problems where the best known quantum algorithm is asymptotically better than the best known classical algorithm but, as far as I've heard, nobody has ever found a case where the best quantum algorithm can be proved to be better than the best classical algorithm. So there's always going to be a danger of this happening no matter what problem you attack.

Isn't quantum factoring proven to be exponentially faster than the best known classical one? The only question is we don't know if there is a better classical factoring algorithm. Wikipedia: > On a quantum computer, to factor an integer N, Shor's algorithm runs in polynomial time. This is almost exponentially faster than the most efficient known classical factoring algorithm, the general number field sieve, which wor…

The other thing we don't know is whether it's physically possible to build a quantum computer capable of it. As opposed to a theoretical ideal quantum computer.

The thing that gets smoothed over with QC is managing the error rates and the fact that it hasn't been shown to be physically possible to scale up computation without the error rates also scaling up exponentially and making the thing useless.

Re: IBM casts doubt on Google's claims of quantum supremacy

#47

Post by Invictus0 »

hktuotroi wrote: post #40
mellosouls wrote: post #21

Repeating my question from the other thread: If IBM can cast doubt by describing a 2.5 day classical run, why not just do that instead, and blow the claim out of the water? There were a couple of responses (thanks) but I still don't understand - it looks like it's not as easy as they imply.

They didn't say 2.5 days on a laptop. They probably mean on a bunch of datacenters together. That is expensive. Google implied their supremacy over all of the world computers combined together.

They are talking about 2.5 days on the world's most powerful super computer, which Google had previously claimed would take 10,000 years to complete the task.

Re: IBM casts doubt on Google's claims of quantum supremacy

#48

Post by htfu »

Arkhaine_kupo wrote: post #25
excalibur wrote: post #7

Earlier quoted context omitted.

But it's still pretty fuzzy. If we agree that 10,000 years on a classical system is supremacy but 2.5 years isn't, where's the cutoff? 25 years? 250? An average human lifespan? Edit: Thanks guys for pointing out where I misread the article, leaving mistake intact so the replies make sense.

The cutoff is on a complexity level. IBM claims it is linear complexity so that is easily solved in a classical computer, regardless of the time it takes. Google's claim is that it is exponential which means they achieved quantum supremacy or proven a quantum processor that can solve a problem a classical processor cannot.

Yes, but the interesting thing to me is how that cutoff between linear and exponential complexity comes down not to the processor but other computing resources.

Meaning when supremacy soon is demonstrated even accounting for storage, it should be able to be undone for a while yet by, say, appropriating everyone’s phones and fridge storage, Silicon Valley style.

Re: IBM casts doubt on Google's claims of quantum supremacy

#50

Post by andrewla »

Also of note is Gil Kalai's updated take on the experiment [1]. The heart of the complaint is that the quantum computer's solution to this problem relies on a calibration process, which is done on a classical computer and requires resources orders of magnitudes higher than the quantum portion of the computation:

> The Google experiment actually showed that a quantum computer running for 100 seconds PLUS a classic computer that runs 1000 hours can compute something that requires a classic computer 10 hours.

EDIT: Just as a note, lest you dismiss Kalai as an outsider/crackpot, you can look at the researchers who show up in the comments on the blog post.

[1] https://gilkalai.wordpress.com/2019/10/13/the-story-of-poinc...

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