Precise Calibrations of Few-Body Physics in Potassium-39: Experiment and Theory

Ultracold atoms provide a versatile toolbox for the study of diverse quantum phenomena. The minimal platform to present quantum mechanics is at single particle level. Two-particle inter-ference effects such as Hanbury Brown-Twiss are a consequence of the particle statistics. Exotic quantum effects in which statistics and interactions are combined appear in three-particle systems as elucidated by e.g. Efimov in the early 1970s. Efimov’s work can be further extended to four- or five-particle systems and applied to general dilute quantum gases in the weakly interacting regime. In the many-body context, it may also assist the analysis of quench dynamics in unitary gasses where perturbation theory breaks down.

A systematic study of few-body physics is made possible by the use of magnetic Feshbach resonances. One can greatly benefit from the improved experimental precision when comparing the observables to generic few-body models. In this thesis, I begin by describing the efforts we spent on achieving overall robustness and accuracy on our potassium-39 quantum gas machine, including the hardware upgrades we made for future scientific projects. Then following a brief review on the realization of Efimov physics in cold atoms, I expand on a series of scattering experiments we performed to understand few-body physics with effectively repulsive inter-particle interactions, as a complement to our previous investigations of the attractive-interaction regime. At the end, I combine our knowledge from both regimes together to discuss the global picture of Efimov physics in homonuclear systems at a beyond proof-of-principle level.
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Department of Physics
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University of Colorado Boulder
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