Quantum transport and control of atomic motion with light
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This dissertation describes our experimental investigations of quantum transport and atomic motion control using optical potentials. The system we study consists of ultracold sodium atoms under the influence of light forces. First, we introduce the dynamics of neutral atoms in a periodic optical potential. The system resembles the textbook problem of an electron inside the crystalline lattice, and we review the main characteristics of the interaction for the atom optics case. In particular, atoms trapped in a lattice subject to large accelerations undergo Landau-Zener tunneling, process which makes the system unstable. The number of atoms trapped in the potential shows the characteristic exponential decay over time. However, deviations from this law are predicted by quantum mechanics. We use the experimental access to the non-exponential time to demonstrate the Quantum Zeno and Anti-Zeno effects. These effects show the influence of frequent observations on the decay rate of a quantum unstable system. The second part of the dissertation introduces a new system we plan to study, namely, the quantum interaction between sodium atoms in the ground state and a conductive surface. We are interested in the measurement of the Casimir-Polder potential with a precision of better than 1%. In order to do this, we have chosen to launch the atoms towards the surfaces at very small incident velocities (a few mm/s), and measure the influence of the interaction on the reflection probability. Atoms reflect from the purely attractive potential due to quantum reflection, an effect with no classical analogy. The experimental observation of quantum reflection requires atomic distributions with temperatures below 1 μK. For this purpose, we have pro- duced and studied a Bose-Einstein condensate (BEC) with sodium atoms. The region where the BEC is created is separated spatially form the surfaces by a distance of 10 cm, vertically. In order to bring the atoms close to the surfaces prior to their launching, we have developed an optical elevator. The eleva- tor uses a moving optical lattice in the regime where tunneling is negligible. Results of the macroscopic optical transport technique, and current progress towards a measurement of the Casimir-Polder interaction, are reported.