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Comment by taejo | Hacker News Reader

The lamp is not a programmable light-processor that can compute arbitrary computation using light, but Sycamore is (though it's very small).

The trouble is we don't know many (any?) interesting algorithms to run on such processors. We can factor prime numbers using Shor's algorithm, but the numbers we can factor with 54 qubits are so small that our best non-quantum algorithms on our best non-quantum computers far outperform them. No supremacy is demonstrated. It's only when one takes problems that are ideally suited to run on this processor that it outperforms classical computers.

Even with the deck stacked this way, it's taken until 2019 for it to be done for the first time! It's a very, very early milestone.

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That does make sense, but given that the task is not solving anything "outside" the physical process itself, it still feels unfulfilling. Using my (maybe wrongheaded) analogy: it feels like "we built a lamp to simulate what happens when we turn on a lamp".

Quantum "supremacy" only feels like a real thing when a quantum computer can solve a problem that isn't directly tied to the simulation of itself. That's my feeling, anyway.

BTW: this is not to disparage the work itself. This seems like great research, and great progress in this field. Good on Google and the researchers!

> That does make sense, but given that the task is not solving anything "outside" the physical process itself, it still feels unfulfilling. Using my (maybe wrongheaded) analogy: it feels like "we built a lamp to simulate what happens when we turn on a lamp".

While that's true, there are a great many physics researchers who are extremely interested in quantum effects. A computer that quickly simulates quantum circuitry, if only for study / practice, is still extremely useful.

In effect: a lamp isn't very important because most engineers and researchers already knows how a lamp works. But quantum circuits are itself an interesting, barely-studied, field with few experts truly understanding it yet.

I agree that the term "quantum supremacy" is overly grandiose, but it was clearly defined before Google published this work.

I just want to emphasise that there were people who believed that even this small step was impossible. Prominent quantum-computing skeptic Gil Kalai believes that scalable quantum computing is impossible in principle, and believes that this paper didn't achieve what it claims, but he says that his view would be refuted if they did! (This is in contrast to IBM, who isn't criticizing the quantum side of the experiment, but the comparison to classical computing; and to the Internet commentariat who are saying that even if they did everything they claim, it's not interesting).

Exactly. If we could design some cool lens-refraction based punch card, such that when you shone your desk lamp through it, it solved some very hard problem, then that would also be an incredibly cool solution.

Funnily enough, something similar has been done with neural networks "physical-ized" in special glass panes.

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-7-8-8...

This is the most amazing thing I’ve seen all day!

Has something like this been actually demonstrated beyond the theoretical possibility?

Can Sycamore compute an arbitrary computation? That's the first I've heard this claim. They say it's "programmable" but I read that as some kind of weak configurability rather than "this is a quantum computer capable of computing any (54 qubit) quantum algorithm."

I don't know. I simply made the opposite assumption from you.

EDIT: it looks like it only has a single, weird, type of gate. But I guess the connections between gates are configurable? Still different to a lamp!

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