Probing the spectral density of a dissipative qubit via quantum synchronization

TL;DR

This paper presents a method to infer the spectral density of an environment affecting a qubit by observing quantum synchronization phenomena between the qubit and a probe, enabling environment characterization without direct measurement.

Contribution

The authors introduce a novel probing scheme utilizing quantum synchronization transitions to reconstruct the spectral density of a dissipative environment affecting a qubit.

Findings

Synchronization transition reveals spectral density features

Monitoring probe dynamics suffices for environment inference

Method enables non-invasive spectral analysis

Abstract

The interaction of a quantum system, which is not accessible by direct measurement, with an external probe can be exploited to infer specific features of the system itself. We introduce a probing scheme based on the emergence of spontaneous quantum synchronization between an out-of-equilibrium qubit, in contact with an external environment, and a probe qubit. Tuning the frequency of the probe leads to a transition between synchronization in phase and antiphase. The sharp transition between these two regimes is locally accessible by monitoring the probe dynamics alone and allows one to reconstruct the shape of the spectral density of the environment.