Time-adaptive single-shot crosstalk detector on superconducting quantum computer

TL;DR

This paper introduces a time-adaptive, single-shot crosstalk detection method for superconducting quantum computers that uses spectator qubits and quantum coherence to improve detection accuracy in noisy, multi-user environments.

Contribution

It proposes a novel detection technique leveraging spectator qubits and quantum coherence, outperforming previous methods in real-device noise scenarios.

Findings

Achieves high detection success probability of over 85% in simulated real-device noise.

Outperforms previous constant-frequency detection methods in success rate.

Effective in detecting sparse, random crosstalk within a time window.

Abstract

Quantum crosstalk which stems from unwanted interference of quantum operations with nearby qubits is a major source of noise or errors in a quantum processor. In the context of shared quantum computing, it is challenging to mitigate the crosstalk effect between quantum computations being simultaneously run by multiple users since the exact spatio-temporal gate distributions are not apparent due to privacy concerns. It is therefore important to develop techniques for accurate detection and mitigation of crosstalk to enable high-fidelity quantum computing. Assuming prior knowledge of crosstalk parameters, we propose a time-adaptive detection method leveraging spectator qubits and multiple quantum coherence to amplify crosstalk-induced perturbations. We demonstrate its utility in detecting random sparsely distributed crosstalk within a time window. Our work evaluates its performance in two scenarios: simulation using an artificial noise model with gate-induced crosstalk and always-on idlings channels; and the simulation using noise sampled from an IBM quantum computer parametrised by the reduced HSA error model. The presented results show our method's efficacy hinges on the dominance of single-qubit coherent noise across channels, and the impact of angle mismatching is suppressed as spectator qubits increase. From simulation using real-device noise parameters, our strategy outperforms the previous constant-frequency detection method of Harper et. al. [arXiv: 2402.02753 (2024)] in the detection success rate, achieving an average detection success probability of $0.852\pm 0.022$ (equally scaled noise channels) and $0.933\pm0.024$ (asymmetrically scaled noise channels) from 1 to 7 crosstalk counts.