Imperfection analyses for random-telegraph-noise mitigation using spectator qubits

TL;DR

This paper analyzes the robustness of a spectator qubit-based noise mitigation protocol against real-world imperfections, deriving bounds where performance remains effective.

Contribution

It extends the adaptive noise mitigation protocol to account for practical imperfections, providing analytical bounds for effective decoherence suppression.

Findings

Imperfection bounds where decoherence suppression remains effective

Analytical methods for Bayesian estimation in non-ideal scenarios

Generalized formalism for non-ideal noise mitigation analysis

Abstract

Spectator qubits (SQs) for random-telegraph noise mitigation have been proposed by Song et al., Phys. Rev. A, 107, L030601 (2023), where an SQ operates as a noise probe to estimate optimal noise-correction control on the hard-to-access data qubits. It was shown that a protocol with adaptive measurement on the SQs and a Bayesian estimation-based control can suppress the data qubits' decoherence rate by a large factor with quadratic scaling in the SQ sensitivity. However, the protocol's practicality in real-world scenarios remained in question, due to various sources of imperfection that could affect the performance. We therefore analyze here the proposed adaptive protocol under non-ideal conditions, including parameter uncertainties in the system, efficiency and time delay in readout and reset processes of the SQs, and additional decoherence on the SQs. We also explore analytical methods of Bayesian estimation in the time domain and generalize the map-based formalism to non-ideal scenarios. This allows us to derive imperfection bounds at which the decoherence suppression remains approximately the same as under ideal conditions.