Benchmarking quantum logic operations for achieving fault tolerance
Abstract
Contemporary methods for benchmarking noisy quantum processors typically measure average error rates or process infidelities. However, thresholds for faulttolerant quantum error correction are given in terms of worstcase error rates  defined via the diamond norm  which can differ from average error rates by orders of magnitude. One method for resolving this discrepancy is to randomize the physical implementation of quantum gates, using techniques like randomized compiling (RC). In this work, we use gate set tomography to perform precision characterization of a set of twoqubit logic gates to study RC on a superconducting quantum processor. We find that, under RC, gate errors are accurately described by a stochastic Pauli noise model without coherent errors, and that spatiallycorrelated coherent errors and nonMarkovian errors are strongly suppressed. We further show that the average and worstcase error rates are equal for randomly compiled gates, and measure a maximum worstcase error of 0.0197(3) for our gate set. Our results show that randomized benchmarks are a viable route to both verifying that a quantum processor's error rates are below a faulttolerance threshold, and to bounding the failure rates of nearterm algorithms, if  and only if  gates are implemented via randomization methods which tailor noise.
 Publication:

arXiv eprints
 Pub Date:
 July 2022
 arXiv:
 arXiv:2207.08786
 Bibcode:
 2022arXiv220708786H
 Keywords:

 Quantum Physics