Assessing Spatiotemporally Correlated Noise in Superconducting Qubits via Pulse-Based Quantum Noise Spectroscopy

TL;DR

This paper introduces a nonparametric quantum noise spectroscopy protocol to accurately characterize spatiotemporally correlated noise and crosstalk in two-qubit systems, improving noise understanding for quantum error correction.

Contribution

The paper presents a novel pulse-based QNS method that reconstructs real and imaginary parts of the two-qubit cross-spectrum, outperforming existing protocols in characterizing correlated noise.

Findings

Successfully reconstructs spectra of engineered correlated noise.

Outperforms existing comb-based QNS protocols.

Demonstrates utility in noise characterization for quantum error correction.

Abstract

Spatiotemporally correlated errors are widespread in quantum devices and are particularly adversarial to error correcting schemes. To characterize these errors, we propose and validate a nonparametric quantum noise spectroscopy (QNS) protocol to estimate both spectra and static errors associated with spatiotemporally correlated dephasing noise and fluctuating quantum crosstalk on two qubits. Our scheme reconstructs the real and imaginary components of the two-qubit cross-spectrum by using fixed total time pulse sequences and single qubit and joint two-qubit measurements to separately resolve spatially correlated noise processes. We benchmark our protocol by reconstructing the spectra of spatiotemporally correlated noise processes engineered via the Schr\"{o}dinger Wave Autoregressive Moving Average technique, emulating dephasing errors. Furthermore, we show that the protocol can outperform existing comb-based QNS protocols. Our results demonstrate the utility of our protocol in characterizing spatiotemporally correlated noise and quantum crosstalk in a multi-qubit device for potential use in noise-adapted control or error protection schemes.