Multi-loop feedback control for atom laser coherence

Abstract

In this paper we present a multi-loop measurement feedback control scheme to improve atom laser coherence. The first loop (proposed by Thomsen and Wiseman, 2002) aims to cancel the decohering effects of the nonlinear atom-atom interactions via direct measurement feedback. However, there are nonlinear interactions with the optical probe field used in the measurement scheme which may also contribute to a degradation in atom laser performance. Accordingly, we introduce a second feedback loop to implement a LQG controller to reduce these effects. The multi-loop design achieves improved atom laser coherence.