Noise Thermometry with Two Weakly Coupled Bose-Einstein Condensates

TL;DR

This paper demonstrates a novel thermometry method using phase fluctuations between two weakly coupled Bose-Einstein condensates, confirming deviations in heat capacity consistent with quantum thermodynamics.

Contribution

It introduces a new experimental approach to measure temperature via phase noise in coupled BECs, enabling thermometry where traditional methods are ineffective.

Findings

Phase fluctuations depend on temperature and coupling strength.

The method accurately measures temperature in challenging regimes.

Heat capacity of an ideal Bose gas deviates from classical predictions.

Abstract

Here we report on the experimental investigation of thermally induced fluctuations of the relative phase between two Bose-Einstein condensates which are coupled via tunneling. The experimental control over the coupling strength and the temperature of the thermal background allows for the quantitative analysis of the phase fluctuations. Furthermore, we demonstrate the application of these measurements for thermometry in a regime where standard methods fail. With this we confirm that the heat capacity of an ideal Bose gas deviates from that of a classical gas as predicted by the third law of thermodynamics.