Quantum optics with 87Rb vapour in the hyperfine Paschen-Back regime

Abstract

We present experimental studies of quantum optics with Rb vapour in the hyperfine Paschen-Back (HFPB) regime. We use a magnet to enter the HFPB regime, where, for Rb, the atomic transitions are separated by more than their Doppler width. This allows us to create clean 3- or 4-levels systems, which we model simply and effectively by solving the Lindblad master equation. We study electromagnetically induced transparency in a V configuration in the HFPB, where we see large, clean absorption and corresponding transmission features. We model the system, and use the model to understand the role of coherence in the features seen. We carry out seeded four-wave mixing in a double ladder scheme (5S--5P--5D), both in and out of the HFPB regime, and compare the two regimes. The simplicity of the system in the HFPB regime allows us to model the system to understand the features we see in the experimental spectra. We convert our seeded FWM into spontaneous FWM, which we use to produce pairs of heralded single photons. We find the zero-field regime to be more efficient for the production of these pairs, and measure , demonstrating that this is a single photon source. Throughout, we make use of lens cavity etalon filters, which we commission, characterise and compare to atomic line filters. We investigate fine structure changing collisions, which transfer atoms between 5P states, and can be a significant source of noise for quantum optics experiments in thermal vapours. We deduce that these are Rb-buffer gas collisions, measure the spectra of the fluorescence produced after a collision, and use the resolved spectra of the HFPB regime to determine that the nuclear spin magnetic quantum number, , is preserved in these collisions.