jlokier has explained this beautifully and in more detail than I would have known how. I will just add one thing: basically Quantum Supremacy is yet another te

jlokier has explained this beautifully and in more detail than I would have known how. I will just add one thing: basically Quantum Supremacy is yet another test of QM. As long as quantum supremacy could not be demonstrated, there remained a possibility that QM was wrong in this prediction - just like until the Higgs boson was detected, there remained a possibility that the Standard Model was wrong/incomplete. If you're curious of some proposed possible barriers to quantum supremacy from the time before this experiment was completed, Gil Kalai is a major advocate of the impossibility of achieving QS in practice. This paper [0] details some of this arguments. In very short, his argument is that it is fundamentally impossible to control quantum states to a sufficient degree of precision to realize an actual quantum computer, that errors will always compound too much (he doesn't believe the Google paper will stand the test of time). I am not a believer in his view, but as far as I understand it is (or was, before the Google experiments) not completely absurd; and it is definitely not supernatural. [0] https://arxiv.org/abs/1908.02499 https://arxiv.org/abs/1908.02499