Quantum thermometry in action: Enhanced release–recapture thermometry in ultracold gases

Speaker: Dr Luis A. Correa (Dept of Physics and Astronomy, University of Exeter)

Title: Quantum thermometry in action: Enhanced release–recapture thermometry in ultracold gases

Abstract: A single cold atom can be trapped in the waist of an optical tweezer. Such trapping potential can be manipulated, and the atom can be placed in thermal contact with heat baths (e.g., a nearby Bose–Einstein condensate). These are most of the necessary elements for setting up and running a quantum-thermodynamic engine or refrigeration cycle. The key missing ingredient is a means to reliably take the temperature of that trapped atom, especially when dealing with scarce data. Here, we introduce a Bayesian estimation protocol for optimal 'global quantum thermometry' in thermal equilibrium. We then show how temperature estimates on few atoms based on the release–recapture method, can be substantially sped up — thus minimising the number of necessary destructive measurements — when processed with our recently proposed Bayesian technique as opposed to the standard method of fitting the data by least squares to a survival-probability model. This will be illustrated experimental data from measurements on trapped single potassium atoms cooled down to few tens of microkelvins.