Enhanced light-atom interaction in an optical resonator

Abstract

Cavity quantum electrodynamics is a powerful platform for manipulating photonƯatom interactions. In this thesis, we explore its applications in photonic and atomic state preparation. With an optical cavity and an ensemble of cesium atoms, we demonstrate that, for two light fields [psi]s (signal) and [psi]A (ancilla) that have only weakly interacted with one another, measurements on the ancilla can produce substantial conditional change on 7./is. We observe conditional signal power changes over a large range of 30 (by factor between 0.1 and 3.2), and phase shift up to [pi]/2, induced by measurements in different ancilla bases. The highest power gain of 3.2 is achieved with a success probability of 3%. The method allows one to modify or boost a given interaction by trading in success probability for interaction strength, and is generically applicable to a variety of systems. Next, we move on to atomic state preparation. We demonstrate cavity cooling of an ensemble of 200 cesium atoms to the theoretical limit. Within 200 ms, the atomic temperature is reduced from 200 [mu] 10 [mu]K, mainly determined by the cavity linewidth. The cavity cooling performance is largely independent to the atomic energy structure. This in principle makes it possible to apply the technique to molecules and atoms with complex internal energy structure. We further cool the atomic ensemble to quantum degeneracy with Raman sideband cooling. To suppress the unfavorable two-body and three-body loss rate of cesium, we confine the atoms into a lD geometry. In this lD geometry, cesium atoms with a large negative scattering length form a metastable state known as a super-TonksƯGirardeau (sTG) gas. We calibrate for the first time the two-body and three-body short-range correlations of the gas. Compared to a three-dimensional non-interacting Bose gas, the g(2) and g(3) correlations of the sTG gas are reduced by a factor of 5 and 130, respectively.