Regarding Google's "quantum supremacy" paper, we argue that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity. This is in fact a conservative, worst-case estimate, and we expect that with additional refinements the classical cost of the simulation can be further reduced.
Quantum computing is at the threshold of tackling important problems that cannot be efficiently or practically computed by other, more classical means. Getting past this threshold will require us to build, test and operate reliable quantum computers with 50 or more qubits. Achieving this potential will require major leaps forward in both science and engineering. […]