Quantum Resonances in a Bose-Einstein Condensate

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M. Andersen, M. d’Arcy, J. Grossman, K. Helmerson,

C. Ryu, W. Phillips, A. Vaziri

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*National Institute of Standards & Technology,
Atomic Physics Division*

* 100 Bureau Drive, Stop 8424, Gaithersburg, MD 20899-8424, USA*

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The δ-kicked rotor is a paradigm in classical chaos theory, in which a pulsed external torque is applied to a rotor. The quantum analogue of this system exhibits non-classical phenomena such as dynamical localization and quantum resonances, in which the energy transferred to the rotor is less (localization) or greater (resonances) than in the classical case. We experimentally observe quantum resonances by applying kicks, using short pulses of a standing wave of laser light, to a Bose-Einstein condensate of sodium atoms; each pulse diffracts the atoms and populates several momentum states. The system’s dynamics depend on the atoms’ initial quasimomentum, and the time interval between successive kicks. These dynamics can be characterized by the evolution of the atomic momentum distribution with time, and by the dependence of atoms’ mean kinetic energy on the number and time period of the δ-kicks.

We observe the phenomena of dynamical localization and quantum resonances and investigate their parametric dependence. Depending on the quasimomentum and kicking period, low- and high-order quantum resonances and anti-resonances may be observed.