I understand that both have 53 qubit devices, yet it is Google that has demonstrated quantum supremacy (although IBM refutes this!). I'm not sure if this is true but it seems like IBM cannot replicate the quantum circuits and measurements that Google has managed on their device. Please correct me if this assumption is wrong.
Reading the Google paper, the following line was significant
Our largest random quantum circuits have 53 qubits, 1,113 single-qubit gates, 430 two-qubit gates, and a measurement on each qubit, for which we predict a total fidelity of 0.2%.
That fidelity seems pretty good given that you've gone through so many gates. The data on IBM is a bit sketchy but this table seems to suggest that even their IBM-Q System One has 2-qubit gates with an average error of 1.69%. So after 400 odd gates, the fidelity drops below 0.1%. And that's not including the single qubit gates or the measurement at the end.
Is this the ace card that allows Google to demonstrate what they did? Have they out-engineered IBM in producing high fidelity gates or does the advantage come from something else?