Efficient Assessment of Process Fidelity

TL;DR

This paper introduces a hierarchy of approximations for efficiently estimating quantum process fidelity, enabling practical gate optimization on noisy quantum hardware with reduced experimental effort.

Contribution

It presents a novel hierarchy of fidelity approximations that simplifies and accelerates the experimental assessment of quantum gate implementations.

Findings

Faithful approximation to quantum process fidelity developed

Demonstrated optimization of a three-qubit gate on real hardware

Reduced effort in fidelity estimation compared to traditional methods

Abstract

The accurate implementation of quantum gates is essential for the realisation of quantum algorithms and digital quantum simulations. This accuracy may be increased on noisy hardware through the variational optimisation of gates, however the experimental realisation of such a protocol is impeded by the large effort required to estimate the fidelity of an implemented gate. With a hierarchy of approximations we find a faithful approximation to the quantum process fidelity that can be estimated experimentally with reduced effort. Its practical use is demonstrated with the optimisation of a three-qubit quantum gate on a commercially available quantum processor.