Open Quantum Dynamics of Mesoscopic Bose-Einstein ... - Physics

AbstractThe properties of an atomic Bose-Einstein condensate in a double-well potential are investigatedthrough a two-mode analysis. An analytic solution for the semiclassical tunnellingand self-trapping dynamics is compared with numerical simulations of the quantumdynamics, which exhibit collapses and revivals for a closed system. A continuousnon-destructive measurement technique to monitor the Josephson tunnelling oscillationsis presented, in which the condensate in one well dispersively shifts the phase of a coherentprobe beam in proportion to atom-number. The evolution of the resulting homodyne photocurrentand Bloch Q distributions shows that oscillations develop even when the initialstate possesses phase symmetry. The conditional dynamics of the condensate which resultfrom measurement back-action also appear in certain semiclassical formulations. The homodynemeasurement technique is incorporated into a proposed weak-force detector. Amaximally entangled initial state, which is the ground state for a double condensate withstrong attractive atomic interactions, enables a high-precision measurement.The dynamics of quantum many-body multimode systems of interacting bosons aresimulated using phase-space methods. The use of the Wigner technique predicts novelnoise effects in fibre solitons. The positive-P representation is used to simulate the formationof mesoscopic Bose-Einstein condensates via evaporative cooling in three dimensionalatom traps. The results indicate highly non-classical behaviour near the critical point,and provide evidence for the spontaneous formation of vortices. Comparisons with correspondingmean-field calculations reveal large differences between the semiclassical andfully quantum results. Finally, the possibility of future progress with alternative phasespacemethods is considered.4