Statistical analysis on random quantum circuit sampling by Sycamore and Zuchongzhi quantum processors

Random quantum sampling, a task to sample bit-strings from random circuit, is considered one of suitable benchmark tasks demonstrate the outperformance computers even with noisy qubits. Recently, sampling was performed on Sycamore processor 53 qubits [Nature 574, 505 (2019)] and Zuchongzhi 56 [Phys. Rev. Lett. 127, 180501 (2021)]. Here, we analyze compare statistical properties outputs by Zuchongzhi. Using Marchenko-Pastur law Wasssertein distances, find that more closer classical uniform than those Sycamore. Some Zuchongzhi's pass number tests while both show similar patterns in heatmaps bit-strings. It shown samples change little as depth circuits increases. Our findings raise question about computational reliability processors could produce statistically different for same task.