ATOM-PHOTON INTERACTION WITH PHOTON PAIRS OF LONG COHERENCE TIME

Abstract

In this thesis, we perform experiments with a polarization-entangled photon pair source. The photon pairs are generated from non-degenerate four-wave mixing in a laser-cooled atomic ensemble of 87Rb using a cascade decay scheme. We use the narrowband photon pairs as bandwidth tunable single photon source and study the scattering dynamics by strongly focusing the single photons onto a single trapped 87Rb atom. When tuning the photon bandwidth from 6 to 2 times the atomic linewidth, we observe an increase in photon scattering and peak excitation probability. A model that takes the temporal photon shape and bandwidth into account agrees well with the experimental observations. To further increase the interaction probability, we demonstrate a method to compress the spectrum of the heralded single photon using a resonant cavity with a bandwidth similar to the photon bandwidth. This method is in principle lossless, and we compress single photons from 20(2) MHz to 8(2) MHz matching almost the atomic linewidth of 6 MHz. In another experiment, we study quantum jumps. This source enabled us to observe quantum jumps between energy states with an, in principle, unlimited time resolution.