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Control of BECs and Atom Lasers

 

Atom laser obtained from a Bose Einstein condensate by the BEC Group at ANU. Control systems are being developed to stabilise the condensate and control the properties of the atom laser. This is an example of a new quantum technology currently under development.

Stabilization of a Bose-Einstein Condensate

S.D. Wilson, A.R.R. Carvalho, J.J. Hope and M.R. James, Effects of measurement backaction of a Bose-Einstein condensate through feedback, Phys. Rev. A, 76, 013610, 2007

Quantum filtering and control is applied to a particle in a harmonic trap under continuous position measurement to demonstrate stabilization via feedback.

Here is an animation (MOV) of the stabilizing feedback system. It shows convergence to a stationary gaussian state from an initial non-gaussian state.

 

Coherence Control of an Atom Laser

M. Yanagisawa and M.R. James, Multi-loop Feedback Control for Atom Laser Coherence, 2007.

This work uses two feedback loops to improve the coherence of an atom laser beam. The first loop is based on the direct feedback proposed by Thomsen and Wiseman, 2002, to cancel the nonlinear atom-atom interactions. The second loop is designed using LQG methods to compensate for the remaining decohering effects.

Here are two animations demonstrating the improvement acheived using both loops: single loop animation (MOV) and two loop animation (MOV).