Nonequilibrium quantum thermometry with noncommutative system-bath couplings

TL;DR

This paper demonstrates that noncommutative system-bath couplings in a quantum probe can significantly enhance temperature sensitivity at cryogenic temperatures by inducing non-Markovian effects and coherence trapping, useful for high-precision thermometry.

Contribution

It introduces a novel approach using noncommutative couplings to improve quantum thermometry, revealing the role of interference and non-Markovian feedback in sensitivity enhancement.

Findings

Quadratic low-temperature scaling of sensitivity achieved.

Memory effects dominate early nonequilibrium measurements.

Coherence-based measurements are most informative initially.

Abstract

Accurate temperature estimation in the quantum and cryogenic regimes remains a fundamental challenge. Here, we investigate nonequilibrium quantum thermometry using a single-qubit probe coupled to a bosonic bath through noncommuting interaction operators, which unify pure dephasing and dissipative dynamics within a spin-boson model. We show that the interference between these two coupling channels induces strong non-Markovian feedback between populations and coherences, leading to coherence trapping and enhanced thermal sensitivity. Remarkably, by tuning the coupling structure, the probe's temperature sensitivity exhibits a quadratic low-temperature scaling, even under weak coupling. Moreover, while coherence-based measurements are formally suboptimal, they become the most informative in the early nonequilibrium regime, where memory effects dominate. Our findings identify noncommutative system-bath couplings as a practical and tunable resource for achieving high-precision quantum thermometry in realistic open-system architectures.