Quantum Thermometry with Trapped Ions

TL;DR

This paper presents a quantum thermometry protocol using trapped ions, demonstrating optimal temperature estimation via spin measurements and showing enhanced sensitivity with ion chains compared to single ions.

Contribution

It introduces a novel temperature estimation method for ion chains using spin measurements, achieving optimal sensitivity and leveraging non-classical quantum Fisher information.

Findings

Single ion measurement saturates the Cramer-Rao bound.

Ion chains provide a temperature sensitivity plateau.

Quantum Fisher information enhances sensitivity over single ions.

Abstract

We introduce the estimation protocol for detecting the temperature of the transverse vibrational modes of linear ion crystal. We show that thanks to the laser induced laser coupling between the vibrational modes and the collective spin states the estimation of the temperature is carried out by set of measurements of the spin populations. We show that temperature estimation protocol using single ion as a quantum probe is optimal in a sense that the set of state projective measurement saturates the fundamental Cramer-Rao bound. We find a plateau of the maximal temperature sensitivity using ion chain as a quantum probe. Moreover, we show that the non-classical part of the quantum Fisher information could leads to enhancement of the temperature sensitivity compared to the single ion case.