Microwave Dressed Potentials: a coherence control method for an atomic Sagnac Interferometer

Abstract

The process of atomic interferometry relies heavily on the underlying atomic manipulation methods that have been developed over the past few decades. The ability to manipulate the internal state dynamics of atoms, and precisely control their time-space co-ordinates both lend themselves to the improvement of the sensitivities of these devices, allowing for more precise measurements, and more in-depth exploration of the physical world. In this thesis the design of a state-dependent fully trapped interferometric transport is presented, wherein atoms are fully magnetically trapped for the entire duration of an interferometric sequence. Through use of Radio-Frequency dressed potentials, we are able to create a trapping system that is both robust, and able to create state-dependent trap that can be dynamically moved to create the mechanical basis for an interferometer. We also investigate the coherence time of a superposition of hyperfine states loaded into the interferometer, necessary for a Ramsey-Borde sequence, and find it is significantly lower than what would be required to perform interferometry. We then present how this lack in coherence time is due to a mismatch in trapping potentials that arises due to a slight discrepancy between gyromagnetic ratios in the two superpositional states. This mismatch broadens the transition linewidth, leading to a reduction in superposition coherence time. Finally, we lay out the theoretical groundwork, and experimental progress, in realising Microwave-Dressed potentials, which utilise the AC-Stark shift to adiabatically shift the trapping potentials of the atoms, reducing the mismatch and thus increasing the coherence time of the superposition.