[Show abstract][Hide abstract] ABSTRACT: We report an experimental study of quantum transport for atoms confined in a periodic potential and compare between thermal and Bose-Einstein condensation (BEC) initial conditions. We observe ballistic transport for all values of well depth and initial conditions, and the measured expansion velocity for thermal atoms is in excellent agreement with a single-particle model. For weak wells, the expansion of the BEC is also in excellent agreement with single-particle theory, using an effective temperature. We observe a crossover to a new regime for the BEC case as the well depth is increased, indicating the importance of interactions on quantum transport.
[Show abstract][Hide abstract] ABSTRACT: We study the effect of different heating rates on a dilute Bose gas confined in a quasi-1D finite, leaky box. An optical kicked rotor is used to transfer energy to the atoms while two repulsive optical beams are used to confine the atoms. The average energy of the atoms is localized after a large number of kicks and the system reaches a nonequilibrium steady state. A numerical simulation of the experimental data suggests that the localization is due to energetic atoms leaking over the barrier. Our data also indicates a correlation between collisions and the destruction of the Bose-Einstein condensate fraction.
[Show abstract][Hide abstract] ABSTRACT: We report the first observation of the quantum Zeno and anti-Zeno effects in an unstable system. Cold sodium atoms are trapped in a far-detuned standing wave of light that is accelerated for a controlled duration. For a large acceleration the atoms can escape the trapping potential via tunneling. Initially the number of trapped atoms shows strong nonexponential decay features, evolving into the characteristic exponential decay behavior. We repeatedly measure the number of atoms remaining trapped during the initial period of nonexponential decay. Depending on the frequency of measurements we observe a decay that is suppressed or enhanced as compared to the unperturbed system.
[Show abstract][Hide abstract] ABSTRACT: We study the motion of ultra-cold atoms in an accelerating optical lattice. We find that the tunneling dynamics are strongly affected by repeated measurement during the non-exponential time, leading to either inhibition (zeno) or enhancement (anti-zeno) of decay.
Quantum Electronics and Laser Science Conference, 2001. Technical Digest. Summaries of Papers Presented at the; 06/2001
[Show abstract][Hide abstract] ABSTRACT: We report on an experimental study of recoil-induced resonances as a method of velocimetry for cold atomic samples. We present a refined experimental method that greatly improves the sensitivity of the measurement over previous experiments. Using frequency-modulation (FM) spectroscopy techniques we achieve a sensitivity that approaches the shot noise limit. In addition, we present a novel approach to deriving the line shape of the observed signal, based on the concept of quantum transport and tunnelling in motional Bloch bands.
Journal of Optics B Quantum and Semiclassical Optics 01/2001; 3:279-287. · 1.81 Impact Factor