Measurement-enhanced determination of BEC phase transitions

TL;DR

This paper introduces a dispersive measurement technique during evaporative cooling to precisely determine BEC phase transitions, reducing fluctuations and enabling single-shot transition point detection through multiple in-situ measurements.

Contribution

It presents a novel method combining dispersive atom number measurements with in-situ imaging to enhance the accuracy of BEC transition detection and allows continuous probing of phase crossings.

Findings

Dispersive measurements improve transition point accuracy.

Calibration between dispersive and absorption imaging is achieved.

Single-shot transition detection is demonstrated.

Abstract

We demonstrate how dispersive atom number measurements during evaporative cooling can be used for enhanced determination of the parameter dependence of the transition to a Bose-Einstein condensate (BEC). In this way shot-to-shot fluctuations in initial conditions are detected and the information extracted per experimental realization is increased. We furthermore calibrate in-situ images from dispersive probing of a BEC with corresponding absorption images in time-of-flight. This allows for the determination of the transition point in a single experimental realization by applying multiple dispersive measurements. Finally, we explore the continuous probing of several consecutive phase transition crossings using the periodic addition of a focused "dimple" potential.