[skywhopper]

But from the Google blog it sounds like the “problem” they chose boils down to “emulating a quantum computer”. Which doesn’t sound like it’s exactly in the spirit of the test, since the quantum computer can obviously emulate itself—and with zero wasted operations!

[afthonos]

It's exactly the spirit of the test; the missing element is that the circuit they're emulating can scale in qubits. So the question is, if you add one cubit, what happens? Can classical computers keep up? The tests were run on a range of cubits with 50+ being the largest number, which is where the 10,000 year claim comes from. Anything further than that just isn't feasible to compute on classical computers, because they don't scale like that.

So why is this in the spirit of the test? Because this means that there are some problems that can only be efficiently solved by quantum computers. So this establishes "supremacy" in the sense that while a quantum computer can efficiently solve any classical computing problem, a classical computer cannot solve any quantum computing problem.

The distance between having this proof-of-concept and having meaningful speedups on real problems that cannot be matched by classical computers is very large; all this tells you is that it's possible, and looking more might not be a waste.