Multi-path interferometers with ytterbium Bose-Einstein condensates in optical lattices

We present progress on the development of a vertical three-path contrast interferometer with ytterbium Bose-Einstein condensates for a fine structure constant measurement, building upon previous work in a horizontal geometry [1]. Vertically-oriented diffraction beams allow for larger momentum separation and longer interaction times, and thus a more sensitive interferometer. However, the use of a heavy atom creates undesirably large momentum spread in the vertical direction of the BEC source due to gravity. We discuss two techniques that we have used to solve this problem: gravity compensation via a shaped optical potential, and a pulsed optical potential to act as a matter-wave lens resulting in delta-kick cooling (DKC). The DKC technique reduced the vertical momentum spread by a factor of six, and this improvement is further supported by nearly six-fold improvement in the coherence time measurement by Ramsey interferometry [2]. We also present our observations of resonances and anti-resonances in Bloch oscillation efficiency due to multipath Landau-Zener-Stuckelberg interference, together with a theoretical modelling of the effect, for large momentum transfer for high precision interferometry. 

[1] B. Plotkin-Swing, D. Gochnauer, K. McAlpine, E. Cooper, A. Jamison, and S. Gupta, Phys. Rev. Lett. 121, 133201 (2018).

[2] D. Gochnauer, T. Rahman, A. Wirth-Singh, and S. Gupta, (manuscript in preparation)