New techniques for precision atom interferometry and applications to fundamental tests of gravity and of quantum mechanics [electronic resource]

Light-pulse atom interferometry--in which quantum mechanical atomic wave packets are split along two paths and later recombined and made to interfere by sequences of optical pulses--is a remarkably sensitive technique for measuring inertial forces, allowing it to be a valuable tool for applications ranging from fundamental tests of gravity to geodesy and inertial navigation. The inertial sensitivity of an atom interferometer is proportional to its enclosed spacetime area--that is, the product of the spatial separation between the two interferometer paths and the interferometer duration. Therefore, new techniques that allow this spacetime area to be increased are essential in order for atom interferometry to reach its full potential. In this thesis, I describe the development of such techniques. We approach the problem of increasing the interferometer spacetime area on two fronts. First, we implement new methods to increase the momentum transferred by the beam splitters of the interferometer. The velocity difference and therefore the spatial separation of the interferometer paths are proportional to this momentum transfer. Conventional atom optics techniques involve beam splitters that transfer two photon momentum recoils (2 hbar k) to the atoms. I will discuss our realization of large momentum transfer (LMT) beam splitters that transfer up to 100 hbar k. Second, we have built a 10 m tall atomic fountain that allows the total interferometer duration to be increased to 2 s. Ultimately, we combined LMT atom optics with long-duration atom interferometry in the 10 m atomic fountain, leading to very large spacetime area atom interferometers. In these very large area atom interferometers, the separation between the two atomic wave packets that respectively travel along the two interferometer paths reaches distances of up to 54 cm. Therefore, in addition to offering greatly increased inertial sensitivity, these interferometers probe the quantum mechanical wavelike nature of matter in a new macroscopic regime. I will discuss the techniques we devised to overcome the many technical challenges associated with such interferometers, which in other apparatus have prevented interference from being maintained for path separations larger than 1 cm. I will also describe initial results from the use of our very large area interferometers to test the equivalence principle with Rb-85 and Rb-87 and our plans for further progress in this direction. Very large area atom interferometry requires high laser power and extremely cold atom sources. We have developed a novel high power, frequency doubled laser source at 780 nm that is suitable for atom optics. Also, we have implemented a sequence of matter wave lenses to prepare and measure atomic ensembles with record-low effective temperatures of 50 pK. In addition to applications in atom interferometry, we expect that such an atom source will be broadly useful for a wide range of experiments.

Keywords: Physics.
Advisor: Kasevich Mark A. primary advisor. Thesis advisor
Graham Peter (Peter Wickelgren) advisor. Thesis advisor
Hollberg Leo (Leo William)