ANOTHER QUANTUM COMPUTER ADVANTAGE FROM GOOGLE?

No, not again. Google is claiming another advantage of its 105-qubit quantum computer, Willow.

There is a straightforward test to determine whether a quantum computer is functional. People at Google can run it; it's an almost trivial algorithm.

1) X=0, initialize a qubit, gate, or the whole quantum computer to whatever state you like. Hero, zero means an initial state.

2) Determine X, figure out what that state is.

3) Repeat steps 1) and 2) a large number of times, say 1000-10000.

4) Plot the distribution of X.

5) If the distribution is wide, the computer is not functional. The width of the distribution depends on the implementation.

6) Any laptop, desktop, or supercomputer can produce an extremely narrow distribution, but a quantum computer cannot. There are fundamental reasons why this is happening, and there is no way around them. A quantum device cannot be placed in the same quantum state in a reproducible manner. Yes, you can quote me on that.

A single-qubit fidelity is quoted at better than 99.95%. This number is better than 99.99999999% in the laptop you are using right now, your desktop, supercomputer, cell phone, Apple Watch, etc. The Google number is atrociously low, rendering the whole quantum computer approach idea worthless. Yes, you can quote me on that, too.

#Google #QuantumComputing #GoogleScheiße #QuantumAdvantage #Neven #Devoret

Not again!