Density plot of qubit purity ξ after t =20 kicks as a function of chaos parameter K=kT and nonlinear parameter g for T=2, δ=0.2 and ε=0.5.

Chaotic dynamics of a Bose-Einstein condensate coupled to a qubit Shepelyansky, Martin, Georgot arXiv 0812.5067: "We study the coupling between a qubit and a Bose-Einstein condensate moving in a kicked optical lattice. In the regime where BEC size is smaller than the lattice period, the chaotic dynamics of the BEC is effectively controlled by the qubit state. This gives an example of exponentially sensitive control over a macroscopic state by internal qubit states. The realization of such coupled systems is within reach of current experimental techniques."

Interference of interacting matter waves Innsbruck arXiv 0812.4836: "The phenomenon of matter wave interference lies at the heart of quantum physics. It has been observed in various contexts in the limit of non-interacting particles as a single particle effect. Here we observe and control matter wave interference whose evolution is driven by interparticle interactions. In a multi-path matter wave interferometer, the macroscopic many-body wave function of an interacting atomic Bose-Einstein condensate develops a regular interference pattern, allowing us to detect and directly visualize the effect of interaction-induced phase shifts. We demonstrate control over the phase evolution by inhibiting interaction-induced dephasing, and by refocusing a dephased macroscopic matter wave in a spin-echo type experiment. Our results show that interactions in a many-body system lead to a surprisingly coherent evolution – possibly enabling narrow-band and high-brightness matter wave interferometers based on atom lasers."

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