Probing The Unitarity of Quantum Evolution Through Periodic Driving

TL;DR

This paper introduces a low-cost method to detect deviations from ideal unitary evolution in quantum systems by analyzing signatures of periodic driving, demonstrated experimentally on a trapped-ion quantum computer.

Contribution

It proposes a novel, scalable approach to diagnose incoherent errors in quantum devices using signatures of periodic driving without full tomography.

Findings

Successfully detected incoherent errors in a trapped-ion quantum computer.

Method requires only repeated measurements of a single observable.

Scales efficiently with the complexity of the quantum dynamics.

Abstract

As quantum computers and simulators begin to produce results that cannot be verified classically, it becomes imperative to develop a variety of tools to detect and diagnose experimental errors on these devices. While state or process tomography is a natural way to characterize sources of experimental error, the intense measurement requirements make these strategies infeasible in all but the smallest of quantum systems. In this work, we formulate signatures of unitary evolution based on specific properties of periodically driven quantum systems. The absence of these signatures indicates a break either in the unitarity or periodicity condition on the evolution. We experimentally detect incoherent error on a trapped-ion quantum computer using these signatures. Our method is based on repeated measurements of a single observable, making this a low-cost evaluation of error with measurement requirements that scales according to the character of the dynamics, rather than the system size.