Atom-laser coherence via multiloop feedback control

Coherence control is the key to success in the applications of atom-laser beams. A multiloop measurement feedback control scheme is proposed to improve atom-laser coherence. The first loop 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, a second feedback loop is used to reduce these effects based on linear quadratic Gaussian control. The multiloop design achieves improved atom-laser coherence.