Tracking evaporative cooling of a mesoscopic atomic quantum gas in real time

Abstract

The fluctuations in thermodynamic and transport properties in many-body systems gain in importance as the number of constituent particles is reduced. Ultracold atomic gases provide a clean setting for the study of mesoscopic systems; however, the detection of temporal fluctuations is hindered by the typically destructive detection, precluding repeated precise measurements on the same sample. Here, we overcome this limitation by utilizing the enhanced light-matter coupling in an optical cavity to perform a minimally invasive continuous measurement and track the time evolution of the atom number in a quasi two-dimensional atomic gas during evaporation from a tilted trapping potential. We demonstrate sufficient measurement precision to detect atom number fluctuations well below the level set by Poissonian statistics. Furthermore, two-time correlations of the atom number obtained from the real-time measurements shed light on the non-linearity of the evaporation process and the noise sources governing the transport of atoms out of the trapping volume. Our results establish coupled atom-cavity systems as a novel testbed for observing thermodynamics and transport phenomena in mesosopic cold atomic gases and pave the way for cavity-assisted feedback stabilization of atom number and temperature of atomic quantum simulators.

Universal pair-polaritons in a strongly interacting Fermi gas

“…In addition, the ability of the cavity field to couple directly to the pair correlation function in the dispersive regime suggests the possibility to engineer pair-pair interactions mediated by cavity photon exchanges [11], opening an uncharted territory to quantum simulation. Beyond these fundamental questions, the weakly destructive and time-resolved character of the cavity-assisted measurement will be of immediate, practical interest in the study of correlations after quenches, such as spin diffusion [40], repulsively interacting Fermi gases where pairing competes with ferromagnetism [41], or during slow transport processes [42,43], complementing other high-efficiency methods [44]. Last, our work adds the exquisite control over photons of a high finesse cavity to the existing cold molecules toolbox [45], opening the way to dissipation engineering of cold chemistry [46][47][48].…”