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Comment by sp332 | Hacker News Reader

Well I don't want to get into a full-on argument in the comments here, but I 100% disagree with your definition of a quantum computer. If a computer uses quantum logic gates then it's a quantum computer.

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It’s not particularly important how you define the term “quantum computer”, nor have I presented any definition of a "quantum computer" that you can disagree with. The point is that, as I wrote before, regardless of your definition - currently there is no discernible advantage of quantum computers over classical computers in the only metric that matters: computational power. This is what people refer to when they talk about the impossibility of QC. Nobody has demonstrated that physically realizable quantum computers can solve BQP problems in polynomial time, or provide any superpolynomial speedups over classical computers, and there is certainly no proof that this is simply a matter of scale.

Grover's algorithm runs faster than any classical algorithm can https://en.wikipedia.org/wiki/Grover%27s_algorithm and it was first run on quantum hardware in 1998 according to the timeline I posted above. Literally the only difference between the state of the art and quantum supremacy is scale.

Now you are simply posting incorrect or misleading information. There is no existing implementation of Grover's algorithm on quantum hardware that demonstrated any speedup over classical computers. In fact the largest implementation of Grover's algorithm to date, on ibmqx5, has an unusable error rate.

> Literally the only difference between the state of the art and quantum supremacy is scale.

This is simply incorrect. At the moment it's unclear that quantum supremacy can be achieved at any scale whatsoever, and it's certainly possible that it's unachievable even in principle.

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