Estimating the Coherence of Noise
Abstract
Noise mechanisms in quantum systems can be broadly characterized as either coherent (i.e., unitary) or incoherent. For a given fixed average error rate, coherent noise mechanisms will generally lead to a larger worst-case error than incoherent noise. We show that the coherence of a noise source can be quantified by the unitarity, which we relate to the average change in purity averaged over input pure states. We then show that the unitarity can be efficiently estimated using a protocol based on randomized benchmarking that is efficient and robust to state-preparation and measurement errors. We also show that the unitarity provides a lower bound on the optimal achievable gate infidelity under a given noisy process.
Cite
@article{arxiv.1503.07865,
title = {Estimating the Coherence of Noise},
author = {Joel J. Wallman and Christopher Granade and Robin Harper and Steven T. Flammia},
journal= {arXiv preprint arXiv:1503.07865},
year = {2019}
}
Comments
10 pages, 4 figures (v3: various improvements and stronger results)