Coherence-Enhanced Single-Qubit Thermometry out of Equilibrium

Area of Science:

• Quantum thermodynamics
• Metrology
• Statistical mechanics

Background:

• Thermometry in nonequilibrium dynamical regimes faces inherent metrological limits.
• Quantum systems can serve as thermometers, interacting with a thermal bath via Markovian dynamics.
• Initial states of quantum thermometers can possess quantum coherence.

Purpose of the Study:

• To analyze the metrological limits of thermometry in nonequilibrium dynamical regimes.
• To investigate the role of initial quantum coherence in enhancing thermometer precision.
• To determine if finite-time precision can exceed asymptotic precision.

Main Methods:

• Analysis of a finite-dimensional quantum system as a quantum thermometer.
• Modeling Markovian thermalization dynamics with a thermal bath.
• Quantification of thermometer precision using Quantum Fisher Information.
• Analytical derivation for qubit thermometers.

Main Results:

• Quantum coherence in the initial state of a quantum thermometer enhances its precision.
• The precision, quantified by Quantum Fisher Information, is maximized at a finite time during thermalization.
• This finite-time enhanced precision can outperform the precision achieved in the asymptotic regime.
• Demonstrated for qubit thermometers in transient dynamics.

Conclusions:

• Initial quantum coherence is a key resource for improving thermometry precision in dynamic, nonequilibrium settings.
• Transient dynamics offer opportunities for enhanced metrological performance beyond steady-state limits.
• This research provides a theoretical framework for designing more precise quantum thermometers.