Consistency testing for robust phase estimation

TL;DR

This paper introduces consistency checks for robust phase estimation that identify when noise conditions violate assumptions, enhancing the reliability of phase estimates in noisy quantum hardware.

Contribution

It extends robust phase estimation by providing consistency tests that detect when noise thresholds are breached, improving trustworthiness of results.

Findings

Two checks accurately identify unreliable estimates

Checks can be used individually or together for verification

Applicable to common noise models in quantum systems

Abstract

We present an extension to the robust phase estimation protocol, which can identify incorrect results that would otherwise lie outside the expected statistical range. Robust phase estimation is increasingly a method of choice for applications such as estimating the effective process parameters of noisy hardware, but its robustness is dependent on the noise satisfying certain threshold assumptions. We provide consistency checks that can indicate when those thresholds have been violated, which can be difficult or impossible to test directly. We test these consistency checks for several common noise models, and identify two possible checks with high accuracy in locating the point in a robust phase estimation run at which further estimates should not be trusted. One of these checks may be chosen based on resource availability, or they can be used together in order to provide additional verification.