We prepare number stabilized ultracold clouds through the real-time analysis of non-destructive images and the application of feedback. In our experiments, the atom number ${ N\sim10^6}$ is determined by high precision Faraday imaging with uncertainty $\Delta_N$ below the shot noise level, i.e., $\Delta_N <\sqrt{ N}$. Based on this measurement, feedback is applied to reduce the atom number to a user-defined target, whereupon a second imaging series probes the number stabilized cloud. By this method, we show that the atom number in ultracold clouds can be prepared below the shot noise level.
Categories: quant-ph physics.atom-ph