A. Smerzi

Quantum Coherent Atomic Tunneling between Two Trapped Bose-Einstein Condensates

We study the coherent atomic tunneling between two zero-temperature Bose-Einstein condensates (BEC) confined in a double-well magnetic trap. Two Gross-Pitaevskii equations for the self-interacting BEC amplitudes, coupled by a transfer matrix element, describe the dynamics in terms of the interwell phase difference and population imbalance. In addition to the anharmonic generalization of the familiar ac Josephson effect and plasma oscillations occurring in superconductor junctions, the nonlinear BEC tunneling dynamics sustains a self-maintained population imbalance: a novel {open_quotes}macroscopic quantum self-trapping{close_quotes} effect. {copyright} {ital 1997} {ital The American Physical Society}

Discrete solitons and breathers with dilute Bose-Einstein condensates.

We study the dynamical phase diagram of a dilute Bose-Einstein condensate (BEC) trapped in a periodic potential. The dynamics is governed by a discrete nonlinear Schrödinger equation: intrinsically localized excitations, including discrete solitons and breathers, can be created even if the BECs interatomic potential is repulsive. Furthermore, we analyze the Anderson-Kasevich experiment [Science 282, 1686 (1998)], pointing out that mean field effects lead to a coherent destruction of the interwell Bloch oscillations.

Macroscopic quantum fluctuations in the Josephson dynamics of two weakly linked Bose-Einstein condensates

We study analytically the quantum corrections to the Gross-Pitaevskii equation for two weakly linked Bose-Einstein condensates. The goals are (1) to investigate dynamical regimes at the borderline between the classical and quantum behavior of the bosonic field, and (2) to search macroscopic quantum coherence phenomena not observable with other superfluid/superconducting systems. Quantum fluctuations renormalize the classical Josephson oscillation frequencies. Large amplitude phase oscillations are modulated, exhibiting collapses and revivals. We describe an interwell oscillation mode with a vanishing (ensemble averaged) mean value of the observables, but with oscillating mean square fluctuations. We finally discuss the limit in which the classical Gross-Pitaevskii (Josephson) dynamics is recovered.

Kinetic properties of a Bose-Einstein gas at finite temperature

We study, in the framework of the Boltzmann-Nordheim equation (BNE), the kinetic properties of a boson gas above the Bose-Einstein transition temperature

Coherent oscillations between two weakly coupled Bose-Einstein condensates: Josephson effects, π oscillations, and macroscopic quantum self-trapping

T_c

Josephson Effects in Dilute Bose-Einstein Condensates

. The BNE is solved numerically within a new algorithm, that has been tested with exact analytical results for the collision rate of an homogeneous system in thermal equilibrium. In the classical regime (

Exact quantum phase model for mesoscopic Josephson junctions

T > 6~ T_c

BOSE-CONDENSATE TUNNELING DYNAMICS: MOMENTUM-SHORTENED PENDULUM WITH DAMPING

), the relaxation time of a quadrupolar deformation in momentum space is proportional to the mean free collision time

TRANSITIONS IN COHERENT OSCILLATIONS BETWEEN TWO TRAPPED BOSE-EINSTEIN CONDENSATES

\tau_{relax} \sim T^{-1/2}

MACROSCOPIC ANGULAR MOMENTUM STATES OF BOSE-EINSTEIN CONDENSATES IN TOROIDAL TRAPS

. Approaching the critical temperature (