Quantum Thermometry of External Phonon Reservoirs in Driven Open Quantum Systems

TL;DR

This paper explores how a driven quantum system's temperature sensitivity varies non-monotonically with environment coupling, revealing an optimal regime for quantum thermometry using phonon interactions.

Contribution

It introduces a polaron transformation approach to analyze phonon effects beyond weak coupling, identifying an optimal environment interaction for enhanced thermometric precision.

Findings

Quantum Fisher Information peaks at intermediate coupling strength.

Thermometric sensitivity vanishes in ultra-weak and strong coupling limits.

Properly tuned nonequilibrium states can significantly improve sensitivity.

Abstract

We investigate the non-monotonic temperature sensitivity of a coherently driven two-level quantum system coupled to an Ohmic phonon environment. By employing a unitary polaron transformation, we account for phonon-induced renormalization effects that go beyond the standard weak-coupling approximations. Our analysis reveals that the Quantum Fisher Information (QFI) exhibits a prominent peak at an intermediate system-environment coupling strength, identifying an optimal regime for thermal sensing. This behavior emerges from a fundamental competition between environment-induced dissipation enhancement and the exponential suppression of system parameters due to phonon dressing. We demonstrate that while thermometric precision vanishes in both the ultra-weak and strong coupling limits, a properly tuned nonequilibrium steady state can significantly enhance sensitivity. These results suggest that environmental interactions, often viewed as detrimental decoherence sources, can be engineered as a resource to optimize the performance of solid-state quantum thermometers.