Randomized compiling for subsystem measurements

TL;DR

This paper introduces a randomized compiling technique that simplifies and mitigates errors in quantum measurements, making them easier to analyze and improve in quantum computing systems.

Contribution

The paper presents a novel randomized compiling method that transforms complex measurement errors into a simple, analyzable form, enhancing error mitigation in quantum measurements.

Findings

Reduces measurement errors to a confusion matrix model.

Errors become independent of unmeasured qudits.

Effective noise becomes easier to model and mitigate.

Abstract

Measurements are a vital part of any quantum computation, whether as a final step to retrieve results, as an intermediate step to inform subsequent operations, or as part of the computation itself (as in measurement-based quantum computing). However, measurements, like any aspect of a quantum system, are highly error-prone and difficult to model. In this paper, we introduce a new technique based on randomized compiling to transform errors in measurements into a simple form that removes particularly harmful effects and is also easy to analyze. In particular, we show that our technique reduces generic errors in a computational basis measurement to act like a confusion matrix, i.e. to report the incorrect outcome with some probability, and as a stochastic channel that is independent of the measurement outcome on any unmeasured qudits in the system. We further explore the impact of errors on indirect measurements and demonstrate that a simple and realistic noise model can cause errors that are harmful and difficult to model. Applying our technique in conjunction with randomized compiling to an indirect measurement undergoing this noise results in an effective noise which is easy to model and mitigate.