Fast, accurate, and error-resilient variational quantum noise spectroscopy

TL;DR

This paper introduces a new noise spectroscopy method for quantum sensors that is accurate, error-resilient, and requires minimal assumptions, enabling detailed environmental noise characterization at molecular scales.

Contribution

It presents a self-consistent, assumption-minimal approach to reconstruct noise spectra from dynamical decoupling measurements, improving accuracy and robustness over existing methods.

Findings

Reconstructed the noise spectrum of a nitrogen-vacancy sensor in diamond.

Resolved previously undetected nuclear species at the diamond surface.

Showed that earlier measurements overestimated low-frequency noise strength.

Abstract

Detecting and characterizing decoherence-inducing noise sources is critical for developing robust quantum technologies and deploying quantum sensors operating at molecular scales. However, current noise spectroscopies rely on severe approximations that sacrifice accuracy and precision. We propose a novel approach to overcome these limitations. It self-consistently extracts noise spectra that characterize the interactions between a quantum sensor and its environment from commonly performed dynamical decoupling-based coherence measurements. Our approach adopts minimal assumptions and is resilient to measurement errors. We quantify confidence intervals and sensitivity measures to identify experiments that improve spectral reconstruction. We employ our method to reconstruct the noise spectrum of a nitrogen-vacancy sensor in diamond, resolving previously undetected nuclear species at the diamond surface and revealing that previous measurements had overestimated the strength of low-frequency noise by an order of magnitude. Our method uncovers previously hidden structure with unprecedented accuracy, setting the stage for precision noise spectroscopy-based quantum metrology.