Versatile fidelity estimation with confidence

TL;DR

This paper introduces a versatile, measurement-compatible fidelity estimator with confidence guarantees, demonstrated through simulations and experiments on a trapped-ion quantum computer, advancing scalable quantum state verification.

Contribution

It presents a new fidelity estimation method with confidence intervals compatible with any measurement protocol, improving scalability and reliability in quantum device verification.

Findings

Method provides nearly minimax optimal confidence intervals.

Demonstrated effectiveness with trapped-ion quantum computer data.

Competitive in measurement efficiency compared to existing techniques.

Abstract

As quantum devices become more complex and the requirements on these devices become more demanding, it is crucial to be able to verify the performance of such devices in a scalable and reliable fashion. A cornerstone task in this challenge is quantifying how close an experimentally prepared quantum state is to the desired one. Here we present a method to construct an estimator for the quantum state fidelity that is compatible with any measurement protocol. Our method provides a confidence interval on this estimator that is guaranteed to be nearly minimax optimal for the specified measurement protocol. For a well-chosen measurement scheme, our method is competitive in the number of measurement outcomes required for estimation. We demonstrate our method using simulations and experimental data from a trapped-ion quantum computer and compare the results to state-of-the-art techniques. Our method can be easily extended to estimate the expectation value of any observable, such as entanglement witnesses.