Characterization of Noise using variants of Unitarity Randomized Benchmarking

TL;DR

This paper introduces a practical modification of the unitarity randomized benchmarking protocol, called m-URB, enabling its implementation on real quantum devices to characterize noise, including cross-talk errors, using simulations based on IBM-Q data.

Contribution

The paper proposes the m-URB protocol, a practical variant of URB suitable for current quantum devices, and demonstrates its effectiveness in noise characterization and cross-talk detection.

Findings

Validated m-URB with depolarising and bit-flip channels

Developed Ng-URB to analyze native gate noise

Simulated native gate noise using IBM-Q data

Abstract

Benchmarking of noise that is induced during the implementation of quantum gates is the main concern for practical quantum computers. Several protocols have been proposed that empirically calculate various metrics that quantify the error rates of the quantum gates chosen from a preferred gate set. Unitarity randomized benchmarking (URB) protocol is a method to estimate the coherence of noise induced by the quantum gates which is measured by the metric \textit{unitarity}. In this paper, we for the first time, implement the URB protocol in a quantum simulator with all the parameters and noise model are used from a real quantum device. The direct implementation of the URB protocol in a quantum device is not possible using current technologies, as it requires the preparation of mixed states. To overcome this challenge, we propose a modification of the URB protocol, namely the m-URB protocol, that enables us to practically implement it on any quantum device. We validate our m-URB protocol using two single-qubit noise channels -- (a) depolarising channel and (b) bit-flip channel. We further alter the m-URB protocol, namely, native gate URB or Ng-URB protocol, to study the noise in the native gates into which the quantum circuits are compiled in a quantum computer. Using our Ng-URB protocol, we can also detect the presence of cross-talk errors which are correlated errors caused due to non-local and entangling gates such as CNOT gate. For illustration, we simulate the noise of the native gates taking the noise parameter from two real IBM-Q processors.