Atomic motion in optical potentials

This dissertation describes the experimental study of atomic motion in optical potentials. Our system consists of ultra-cold sodium atoms in an optical potential created by a standing wave of light. As we will show, the properties of this system are closely related to those of an electron in a crystal lattice.; First, we describe the study of the transport properties of an atom in an accelerated lattice. For moderate acceleration, we can observe coherent effects in our system that are obscured by short relaxation times in the corresponding condensed matter system. Bloch states and how they are modified by applied static and time-dependent fields are investigated with spectroscopic tools.; For a large acceleration of the lattice, atoms can escape from the trapping potential via tunneling. The behavior of this unstable system may be expected to follow the universal exponential decay law. This exponential law, however, is not fully consistent with quantum mechanics. Initially the number of trapped atoms shows strong non-exponential decay features before evolving into the characteristic exponential decay. We repeatedly measure the number of atoms that remain trapped during the initial period of non-exponential decay. Depending on the time delay between successive measurements we observe a decay that is suppressed or enhanced as compared to the unperturbed system. The experiments described here are the first and only observation of these Quantum Zeno and Anti-Zeno effects in an unstable quantum system.; The manipulation of the atomic motional state, as described here, is based on the exchange of momentum between the atom and the light beams forming the optical potential. An atom, changing its momentum due to the interaction with the optical lattice, will cause a corresponding change of the number of photons in the constituent light beams. We can measure this change of optical power in order to obtain information about the momentum distribution of the atomic sample. The fundamental properties of this method, named the method of recoil-induced resonances, are derived here. Furthermore, a novel experimental method is presented that greatly improves the sensitivity of the measurement.