Improved thermometry of low-temperature quantum systems by a ring-structure probe

TL;DR

This paper demonstrates that ring-structure probes, especially ferromagnetic and antiferromagnetic configurations, significantly enhance the precision of low-temperature quantum thermometry through their unique dynamical and equilibrium properties.

Contribution

It introduces ring-structure probes for quantum thermometry and analyzes their superior precision compared to non-structure probes, revealing new physical mechanisms.

Findings

Ferromagnetic structures improve low-temperature measurement precision at equilibrium.

Antiferromagnetic structures achieve higher dynamical thermometry accuracy than non-structure probes.

Physical mechanisms explaining the enhanced precision are provided.

Abstract

The thermometry precision of a sample is a question of both fundamental and technological importance. In this paper, we consider a ring-structure system as our probe to estimate the temperature of a bath. Based on the Markovian master equation of the probe, we calculate the quantum Fisher information (QFI) of the probe at any time. We find that for the thermal equilibrium thermometry, the ferromagnetic structure can measure a lower temperature of the bath with a higher precision compared with the non-structure probe. While for the dynamical thermometry, the antiferromagnetic structure can make the QFI of the probe in the dynamical process much larger than that in equilibrium with the bath, which is somewhat counterintuitive. Moreover, the best accuracy for the thermometry achieved in the antiferromagnetic structure case can be much higher than that in the non-structure case. The physical mechanisms of above phenomena are given in this paper.