Quantum metrology out of equilibrium

TL;DR

This paper explores how out-of-equilibrium quantum systems, especially qubits, can be used as sensitive probes to estimate environmental parameters, linking quantum coherence to information metrics and applying this to characterize bosonic environments.

Contribution

It introduces a framework connecting quantum Fisher information with residual coherence in out-of-equilibrium quantum probes for environment characterization.

Findings

Quantum Fisher information relates to residual coherence in qubits.

Estimation schemes effectively characterize environmental parameters.

Application to ohmicity parameter of bosonic environments.

Abstract

We address open quantum systems out-of-equilibrium as effective quantum probes for the characterisation of their environment. We discuss estimation schemes for parameters driving a de-phasing evolution of the probe and then focus on qubits, establishing a relationship between the quantum Fisher information and the residual coherence of the probe. Finally, we apply our results to the characterisation of the ohmicity parameter of a bosonic environment.