Resource-Efficient Noise Spectroscopy for Generic Quantum Dephasing Environments

TL;DR

This paper introduces a resource-efficient noise spectroscopy method using repetitive weak measurements via Ramsey interferometry to directly measure the noise spectrum of quantum environments, outperforming traditional techniques in efficiency and range.

Contribution

The paper presents a novel noise spectroscopy technique based on repetitive weak measurements that enables direct and efficient spectrum measurement of quantum environments causing dephasing.

Findings

Efficient measurement of the full noise spectrum without qubit coherence time limitations.

Resource efficiency surpassing correlation spectroscopy, with linear versus quadratic detection time.

Numerical validation for bosonic and spin bath environments.

Abstract

We present a resource-efficient method based on repetitive weak measurements to directly measure the noise spectrum of a generic quantum environment that causes qubit phase decoherence. The weak measurement is induced by a Ramsey interferometry measurement (RIM) on the qubit and periodically applied during the free evolution of the environment. We prove that the measurement correlation of such repetitive RIMs approximately corresponds to a direct sampling of the noise correlation function, thus enabling direct noise spectroscopy of the environment. Compared to dynamical-decoupling-based noise spectroscopy, this method can efficiently measure the full noise spectrum with the detected frequency range not limited by qubit coherence time. This method is also more resource-efficient than the correlation spectroscopy, as for the same detection accuracy with $N$ sampling times, it takes total detection time $O(N)$ while the latter one takes time $O(N^2)$. We numerically demonstrate this method for both bosonic and spin baths.