Preparation of ultracold atom clouds at the shot noise level

TL;DR

This paper demonstrates a method to prepare ultracold atom clouds with atom number fluctuations below the shot noise level using real-time non-destructive imaging and feedback control.

Contribution

It introduces a real-time feedback technique based on high-precision Faraday imaging to stabilize atom numbers below shot noise in ultracold clouds.

Findings

Atom number uncertainty achieved below shot noise level

Real-time feedback effectively stabilizes atom number

Method applicable for precise control in ultracold atom experiments

Abstract

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.