Optimal Quantum Thermometry by Dephasing

TL;DR

This paper explores how quantum dephasing can be used for optimal thermometry, demonstrating the conditions under which different quantum states and measurement strategies achieve the best temperature sensitivity.

Contribution

It establishes the optimal measurement strategy for quantum thermometry using dephasing and analyzes the conditions for quantum advantage over classical limits.

Findings

Ramsey measurement is optimal for uncorrelated particles.

Metrological equivalence of product and entangled states holds under optimal measurement.

Quantum limit can be surpassed when the parameter ta<1.

Abstract

Decoherence often happens in the quantum world. We try to utilize quantum dephasing to build an optimal thermometry. By calculating the Cram$\acute{e}$r-Rao bound, we prove that the Ramsey measurement is the optimal way to measure the temperature for uncorrelated particles. Using the optimal measurement, the metrological equivalence of product and maximally entangled states of initial quantum probes that always holds. However, using Ramsey measurement, the metrological equivalence only holds in special situation. Contrary to frequency estimation, the quantum limit can be surpassed under the case $\nu<1$. For the general Zeno regime($\nu=2$), uncorrelated product states are the optimal choose in typical Ramsey spectroscopy set-up. In order to surpass the standard scaling, we propose to change the interaction strength with time. Finally, we investigate other environmental influences on the measurement precision of temperature. Base on it, we define a new way to measure non-Markovian effect.