Transport and resonances in kicked Bose-Einstein condensates

Abstract

Scope and Method of Study: A purpose of this research was to study the scaling behavior of resonances of a periodically kicked quantum system. Specifically, a model known as a quantum delta-kicked rotor (QDKR) was implemented with a 87 Rb Bose-Einstein Condensate. Two variants of this system, a quantum delta-kicked accelerator (QDKA) and a quantum ratchet, were also realized experimentally and used to study quantum transport. Furthermore, experiments were undertaken to introduce mean-field interactions in these systems through an Optical Feshbach resonance.

Findings and Conclusions: An overlap or fidelity measurement between a resonant and an off-resonant state of the QDKR yielded a scaling that was dependent on the cube of the measurement time, in units of kicks. Such a sub-Fourier behavior was also calculated to appear in the presence of an acceleration, and was verified experimentally. Quantum accelerator modes were observed in the QDKA and a detailed study of the parameter dependencies of three higher order resonances was done. The modes were explained with two models: a wavefront rephasing model and a quasi classical analysis. A quantum ratchet was realized at a QDKR resonance and the dependence of the directed momentum current on the momentum of the initial state investigated. Finally, photoassociation spectroscopy was performed on a 87 Rb Bose-Einstein condensate for the 1 g and 0 - g long range molecular states to realize an Optical Feshbach resonance.