Feedback control of evaporative cooling through continuous nondestructive measurement

Dispersive coupling of an ultracold atomic ensemble to a high-finesse optical cavity enables continuous readout of the number of atoms present in the ensemble. Real-time feedback based on this measurement allows for experimental parameters to be varied depending on the instantaneous atom number. I will present recent experiments in which we have implemented such a feedback loop during evaporative cooling of a cloud of ultracold ${}^{87}$Rb, informing the cutoff time of the evaporation. This procedure has the potential to reduce fluctuations in final atom number to below the shot-noise limit. Further, by tuning closer to the strong-coupling regime, the dispersive atom number readout could be made sensitive to single-atom evaporation events, offering a microscopic probe of the evaporation process. In addition to providing a novel technique for improved preparation of atomic ensembles in a broad range of experiments, this work paves the way toward the observation and characterization of the microscopic processes involved in the evaporation of atomic ensembles.