Impurities as a quantum thermometer for a Bose-Einstein condensate

TL;DR

This paper presents a quantum thermometer using impurities to measure Bose-Einstein condensate temperatures below one nanokelvin with high precision, outperforming existing methods while minimally disturbing the system.

Contribution

The authors introduce a novel impurity-based quantum thermometer that leverages quantum Fisher information to achieve superior precision in sub-nK thermometry of Bose-Einstein condensates.

Findings

Achieves higher precision than current thermometry methods in the sub-nK regime.

Uses quantum Fisher information to optimize measurement accuracy.

Provides a minimally invasive temperature measurement technique.

Abstract

We introduce a primary thermometer which measures the temperature of a Bose-Einstein Condensate in the sub-nK regime. We show, using quantum Fisher information, that the precision of our technique improves the state-of-the-art in thermometry in the sub-nK regime. The temperature of the condensate is mapped onto the quantum phase of an atomic dot that interacts with the system for short times. We show that the highest precision is achieved when the phase is dynamical rather than geometric and when it is detected through Ramsey interferometry. Standard techniques to determine the temperature of a condensate involve an indirect estimation through mean particle velocities made after releasing the condensate. In contrast to these destructive measurements, our method involves a negligible disturbance of the system.