Coherent Rydberg excitations and photon correlations in dense thermal vapor cells

Abstract

This thesis describes the second generation of experiments towards a single-photon source concept based on a thermal rubidium vapor in a Rydberg-blockaded microcell. First, the situation is described in the density matrix formalism, and the requirements for the experimental system are derived. Key results of dipolar interactions and the influence of optical cavities are studied to contextualize the major challenges of the concept. In the first experimental part the fabrication of vapor cells and specifically our wedge vapor cell design is studied. Based on the daily experimental operation over several years the design is further improved, and the operational limits are marked out. A novel set of vapor cells with internal optical cavity is fabricated and used in a pilot experiment as a path towards a collectively enhanced, superradiant ensemble. The single-photon source concept optical setup is explained along its full development towards a well characterized and stable platform for all experiments with ns laser pulses that provide sufficient power for GHz Rabi frequencies. Spectroscopic experiments involving a strong light-induced atomic desorption (LIAD) pulse serve as benchmark for the performance of the inverted four-wave mixing (FWM) excitation scheme, and several open questions beyond our current understanding are identified. Finally, the single-photon source concept is tested for its photon statistics, which necessitates a careful analysis of statistical significance in the realm of low total correlation counts.