# Global and local thermometry schemes in coupled quantum systems

## TL;DR

This paper investigates the fundamental limits of temperature estimation in coupled quantum systems, revealing how interactions and particle exchange influence thermometric sensitivity and proposing practical measurement schemes.

## Contribution

It introduces new bounds on quantum thermometry in coupled bosonic modes and proposes experimentally feasible local measurement schemes achieving near-Heisenberg precision.

## Key findings

- Interaction decreases sensitivity with conserved particle number
- Particle exchange enhances thermometric sensitivity
- Locally accessible measurements can approach quantum-limited precision

## Abstract

We study the ultimate bounds on the estimation of temperature for an interacting quantum system. We consider two coupled bosonic modes that are assumed to be thermal and using quantum estimation theory establish the role the Hamiltonian parameters play in thermometry. We show that in the case of a conserved particle number the interaction between the modes leads to a decrease in the overall sensitivity to temperature, while interestingly, if particle exchange is allowed with the thermal bath the converse is true. We explain this dichotomy by examining the energy spectra. Finally, we devise experimentally implementable thermometry schemes that rely only on locally accessible information from the total system, showing that almost Heisenberg limited precision can still be achieved, and we address the (im)possibility for multiparameter estimation in the system.