Characterizing quantum gases in time-controlled disorder realizations using cross-correlations of density distributions

TL;DR

This paper introduces a method to generate and characterize time-controlled optical speckle disorder and investigates its effects on quantum gases, enabling studies of nonequilibrium physics with tunable disorder dynamics.

Contribution

The authors develop an experimental setup for producing and characterizing time-dependent optical speckle disorder and demonstrate its impact on quantum gases through cross-correlation measurements.

Findings

Speckle patterns can be controlled via diffuser rotation.

Density distributions of BECs are correlated across different speckle realizations.

The setup enables tuning disorder to match quantum gas dynamics.

Abstract

The role of disorder on physical systems has been widely studied in the macroscopic and microscopic world. While static disorder is well understood in many cases, the impact of time-dependent disorder on quantum gases is still poorly investigated. In our experimental setup, we introduce and characterize a method capable of producing time-controlled optical-speckle disorder. Experimentally, coherent light illuminates a combination of a static and a rotating diffuser, thereby collecting a spatially varying phase due to the diffusers' structure and a temporally variable phase due to the relative rotation. Controlling the rotation of the diffuser allows changing the speckle realization or, for future work, the characteristic time scale of the change of the speckle pattern, i.e. the correlation time, matching typical time scales of the quantum gases investigated. We characterize the speckle pattern ex-situ by measuring its intensity distribution cross-correlating different intensity patterns. In-situ, we observe its impact on a molecular Bose-Einstein condensate (BEC) and cross-correlate the density distributions of BECs probed in different speckle realizations. As one diffuser rotates relative to the other around the common optical axis, we trace the optical speckle's intensity cross-correlations and the quantum gas' density cross-correlations. Our results show comparable outcomes for both measurement methods. The setup allows us to tune the disorder potential adapted to the characteristics of the quantum gas. These studies pave the way for investigating nonequilibrium physics in interacting quantum gases using controlled dynamical-disorder potentials.