Experiments to control atom number and phase-space density in cold gases



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This dissertation presents the development and implementation of two novel experimental techniques for controlling atom number and phase-space density in cold atomic gases. The first experiment demonstrates the method of single-photon cooling, an optical realization of Maxwell's demon, using an ensemble of rubidium atoms. Single-photon cooling increases the phase-space density of a cloud of magnetically trapped atoms, reducing the entropy of the ensemble by irreversibly transferring atoms through a one-way wall via a single-photon scattering event. While traditional laser cooling methods are limited in their applicability to a small number of atoms, single-photon cooling is much more general and should in principle be applicable to almost all atoms in the periodic table. The experiment described in this dissertation demonstrates a one-dimensional implementation of the cooling scheme. Complete phase-space compression along this dimension is observed. The limitations on the cooling performance are shown to be given by trap dynamics in the magnetic trap. The second part of this dissertation is dedicated to the experiment built to control the atom number of a degenerate Fermi gas on a single particle level. Creating Fock states of atoms with ultra-high fidelity is a mandatory step for studying quantum entanglement on a single atom level. The experimental technique implemented to control the atom number in this experiment is called laser culling. Decreasing the trapping potential reduces the atom number in a controlled way, giving precise control over the number of atoms remaining in the trap. This dissertation details the design and construction of this experiment and reports on the progress towards the creation of neutral lithium Fock states.