Streaming quantum gate set tomography using the extended Kalman filter

TL;DR

This paper introduces a real-time, computationally efficient method using the extended Kalman filter for quantum gate set tomography, enabling fast calibration of quantum processors with minimal computational resources.

Contribution

The authors adapt the extended Kalman filter for streaming quantum gate set tomography, providing a low-cost, real-time estimation method comparable to maximum likelihood estimation.

Findings

Achieves similar accuracy to maximum likelihood estimation

Operates efficiently on standard laptops

Enables real-time calibration of quantum gates

Abstract

Closed-loop control algorithms for real-time calibration of quantum processors require efficient filters that can estimate physical error parameters based on streams of measured quantum circuit outcomes. Development of such filters is complicated by the highly nonlinear relationship relationship between observed circuit outcomes and the magnitudes of elementary errors. In this work, we apply the extended Kalman filter to data from quantum gate set tomography to provide a streaming estimator of the both the system error model and its uncertainties. Our numerical examples indicate extended Kalman filtering can achieve similar performance to maximum likelihood estimation, but with dramatically lower computational cost. With our method, a standard laptop can process one- and two-qubit circuit outcomes and update gate set error model at rates comparable with current experimental execution.