  Quantum computation promises to execute certain computational tasks on time
scales much faster than any known algorithm on an existing classical computer,
for example calculating the prime factors of large integers. Recently a
research team from Google claimed to have carried out such a task with a
quantum computer, demonstrating in practice a case of this so-called quantum
supremacy. Here we argue that this claim was not justified. Unlike other
comments, our criticism is concerned with the missing verification of the
output data of the quantum computation.
