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Comment by bjornsing | Hacker News Reader

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/filename/smalli...

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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.

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?

> But comparing it to manned flight or the first nuclear reactor (...) 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.

Not a lot of people directly own & operate their own airplane, let alone a nuclear reactor, and yet both have had a significant impact on modern life. As for this experiment & QC, only time will tell of course.

I think you misinterpreted "we will ever have them" part. bjornsing is not talking about whether there will be personal quantum computers. It is about whether there will be useful quantum computers at all. That is still open, for example because of issues related to quantum error correction.

Well I don't want to answer for him but you could make the same point with the airplane:

The first flight was 2 people in a plane that lasted very short. I could have ridden my horse more quickly over that distance! How is this a meaningful milestone?!

Well.. it demonstrates something that cannot be done on a horse (classical computer) but that can be done with a plane (quantum computer).

Is the application useful today? Probably not. But that shouldn't discourage anyone.

> 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 completely agree with this statement. This is mainly about Extended Church-Turing Thesis.

The claim here is that they're about to demonstrate QC on a specific hard sampling problem , where one small quantum computer will produce a result in minutes that takes a months on a big cluster of classical computers.

That is still clearly quantum supremacy, even if Shor's algorithm is not yet implementable.

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