UC Berkeley

Atom interferometry is a powerful metrological tool that has been developed over the last few decades. Large momentum transfer (LMT) methodsmanipulate atomic trajectories with tens or hundreds of photon momenta in order to increase sensitivity. This thesis furthers progress towards using LMT methods in next-generation atom interferometers. One main result establishes symmetric Bloch oscillations as a new, viable technique for LMT. Theory and numerics are used to show how the process is coherent and adiabatic, and experimentally we demonstrate coherence in an interferometer with up to 240¯hk, where ¯hk is the momentum of a single photon of 852nm light. This was the second largest coherent momentum splitting demonstrated at at the time of publication. The rest of the thesis focuses on design and construction of a new atomic fountain to measure the fine structure constant α. Discrepancies in recent measurements of α [67, 55] are currently limiting theory predictions for the electron gyromagnetic ratio [25] - an improved measurement of α is therefore highly motivated and would enable an improved test of the consistency of the Standard Model. Previously, our group published a measurement of α at the 0.2 ppb level in 2018 [67]. We built a new experiment with a goal of improving the measurement by a factor of 3-10. Much of the thesis focuses on systematic effects related to spatial intensity inhomogeneities on the laser beam, which are some of the hardest to characterize systematic effects looking forward. A large clear aperture vacuum chamber accommodates larger waist laser beams without clipping on chamber walls. In addition, a high-speed, user-friendly Monte Carlo simulation package was made to predict experimental systematic shifts in the measured value of α due to laser beam inhomogeneities.