Estimation of statistical significance in the quantum supremacy experiment with the Sycamore processor

Google's quantum supremacy experiment is based on sampling of output bitstrings of random quantum circuits [1]. To demonstrate quantum supremacy, it is critical to establish that the hardware fidelity at sampling time is not degraded to zero due to errors and the sampled bitstrings correspond to the expected noisy distribution. In addition, since the run time of classical approximate simulations is proportional to fidelity, it is important to verify that the fidelity is above a threshold at which classical simulation is estimated to be hard. In this talk, I will describe the methodologies for the statistical analyses and show that the bitstring distributions are extremely unlikely to be explained by noise alone and the fidelity is significantly above the threshold.

[1] Quantum supremacy using a programmable superconducting processor, Google AI Quantum and collaborators. Nature 574, 505-510 (2019).