Linear cross-entropy in random circuits

Abstract

Demonstrations of quantum computational advantage and benchmarks of quantum processors via quantum random circuit sampling are based on evaluating the linear cross-entropy benchmark (XEB). We study the behavior of XEB and fidelity using a mapping of average quantities in random quantum circuits to statistical mechanics models. The average value of XEB is shown to be sensitive only to the infidelity of the noisy gates while fluctuations reveal more. "B.W. was supported in part by the DoE ASCR Accelerated Research in Quantum Computing program (award No.~DE-SC0020312)"