Experimental tests of quantum nonlinear dynamics in atom optics

Hensinger, Winfried (2002). Experimental tests of quantum nonlinear dynamics in atom optics PhD Thesis, School of Physical Sciences, The University of Queensland.

       
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Author Hensinger, Winfried
Thesis Title Experimental tests of quantum nonlinear dynamics in atom optics
School, Centre or Institute School of Physical Sciences
Institution The University of Queensland
Publication date 2002
Thesis type PhD Thesis
Supervisor Halina Rubinsztein- Dunlop
Norman R. Heckenberg
Gerard J. Milburn
Total pages 158
Collection year 1999
Language eng
Subjects L
240301 Atomic and Molecular Physics
780102 Physical sciences
Formatted abstract

Cold atoms in optical potentials provide an ideal test bed to explore quantum nonlinear dynamics. Atoms are prepared in a magneto-optic trap or as a dilute Bose-Einstein condensate and subjected to a far detuned optical standing wave that is modulated. They exhibit a wide range of dynamics some of which can be explained by classical theory while other aspects show the underlying quantum nature of the system. The atoms have a mixed phase space consisting of regions of regular motion which appear as distinct peaks in the atomic momentum distribution embedded in a sea of chaos. The action of the atoms is of the order of Planck's constant making quantum effects significant. This thesis presents a detailed description of experiments measuring the evolution of atoms in time dependent optical potentials. Experimental methods are developed providing means for the observation and selective loading of regions of regular motion. The dependence of the atomic dynamics on the system parameters is explored and distinct changes in the atomic momentum distribution are observed which are explained by the applicable quantum and classical theory. The observation of a bifurcation sequence is reported and explained using classical perturbation theory. Experimental methods are developed which provide means to accurately control the momentum of an ensemble of atoms using phase space resonances and chaotic transients and novel ensemble atomic beamsplitters are implemented. The divergence between quantum and classical nonlinear dynamics is manifest in the experimental observation of dynamical tunnelling. It involves no potential barrier. However a constant of motion other than energy still forbids classically this quantum allowed motion. Atoms coherently tunnel back and forth between their initial state of oscillatory motion and the state 180° out of phase with the initial state. The experiments agree well with simulations of the Gross-Pitaevskii equation and the corresponding Floquet theory.

Keyword Quantum optics
Quantum theory
Atoms

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
 
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Created: Fri, 24 Aug 2007, 17:53:56 EST