Southwest Quantum Information and Technology

Versatile fidelity estimation with confidence

Presenting Author: Akshay Seshadri, University of Colorado
Contributing Author(s): Martin Ringbauer, Rainer Blatt, Thomas Monz, Stephen Becker

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 with other methods. Through a combination of theoretical and numerical results, we show various desirable properties for our method: robustness against experimental imperfections, competitive sample complexity, and accurate estimates in practice. Our method can be easily extended to estimate the expectation value of any observable, such as entanglement witnesses.

Read this article online: http://arxiv.org/abs/2112.07925, http://arxiv.org/abs/2112.07947

(Session 9a : Friday from 5:15 pm - 5:45 pm)