Tunable optical potentials for ultra-cold atoms

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Optical techniques allow precise control over the internal and external degrees of freedom in an ultra-cold gas of atoms. For this reason, ultra-cold atoms are often used to simulate other physical systems, especially ones that are typically experimentally challenging or completely inaccessible to manipulation. This proposal aims to create tunable optical potentials for ultra-cold atomic gases. The fundamental goal is to exploit the tunability of ultra-cold gases to create powerful analogies to other physical systems, such as astrophysical and low temperature physics systems, and to further understanding through precise manipulation of ultra-cold atoms. The first phase of this proposal will use optical excitations to study magnetization dynamics in an ultra-cold quantum gas at finite temperature. In such a gas, a superfluid Bose-Einstein condensate coexists with a non-degenerate normal gas component. In particular, the experiments will seek to understand how the presence of spin wave excitations in the uncondensed component affects the coherence of the system and will seek to study instabilities present in these gases. This rich physical system both provides overlap with low temperature physics research and informs the use of trapped gas systems for precision metrology applications. Extending the creation of tunable optical potentials, the second phase of the proposal seeks to induce long-range forces between atoms in an ultra-cold gas using optical techniques. Off-resonant lasers can polarize atoms in an ultra-cold gas, which then interact with each other. Special laser configurations create an interatomic potential that scales inversely with the atomic separation. Such a potential energy has the exact same mathematical form as a gravitational potential, allowing exploration of an artificial, tunable "electromagnetic gravity" in a laboratory setting. This experiment aims to create an analogue to a cold Bose star and use it to study the interplay between this artificial gravity, kinetic energy, and interatomic van der Waals forces.