Optimized mitigation of random-telegraph-noise dephasing by spectator-qubit sensing and control

TL;DR

This paper introduces an optimized Bayesian measurement and control protocol using spectator qubits to effectively mitigate dephasing caused by random telegraph noise, significantly improving quantum coherence.

Contribution

It develops a Bayesian adaptive measurement method for spectator qubits, demonstrating quadratic suppression of decoherence rate and advancing noise mitigation techniques in quantum systems.

Findings

Quadratic suppression of decoherence rate achieved.

Bayesian adaptive protocol outperforms non-adaptive methods.

Spectator qubits effectively mitigate random telegraph noise.

Abstract

Spectator qubits (SQs) are a tool to mitigate noise in hard-to-access data qubits. The SQ, designed to be much more sensitive to the noise, is measured frequently, and the accumulated results used rarely to correct the data qubits. For the hardware-relevant example of dephasing from random telegraph noise, we introduce a Bayesian method employing complex linear maps which leads to a plausibly optimal adaptive measurement and control protocol. The suppression of the decoherence rate is quadratic in the SQ sensitivity, establishing that the SQ paradigm works arbitrarily well in the right regime.