Measuring decoherence and the matter-wave index of refraction with an improved atom interferometer

Abstract

This thesis describes experiments performed using the MIT atom interferometer, which has recently been upgraded to provide increased experimental precision and flexibility. The three-gratings comprising our Mach-Zehnder interferometer have been installed on a vibration isolated platform which has reduced rms motion of the gratings by a factor of two. The arrangement of gratings on the platform can be reconfigured at will, and the entire platform removed from the vacuum chamber for purposes of alignment. We have performed a series of experiments related to decoherence in an atom interferometer. We have explored decoherence due to photon scattering, in particular the transition from single- to multiple-photon decoherence, and have quantitatively verified the decoherence rate constant in the many-photon regime. We have also examined decoherence due to background gas scattering. Finally, we have investigated the distinction between decoherence and classical dephasing by comparing experiments which illustrate each of these phenomena. We have made new measurements of the index of refraction of argon for sodium matter-waves. Our results are twice as precise previous measurements but suffer from significant systematic error. A detailed study of systematics is presented along with concrete proposals for minimizing their effect in future matter-wave index of refraction measurements.