Proposal for an integrated Raman-free correlated photon source

The on-demand generation of identical single photons is one of the most keenly sought capabilities in quantum optics. Such sources are a key resource in optical implementations of quantum information processing, such as quantum communication or computing. Many current heralded single-photon sources use the third order nonlinear optical process of spontaneous four wave mixing, whereby two pump photons are converted into a single photon and an idler photon. These sources can be based on integrated or fibre platforms, but suffer from the spontaneous generation of Raman-shifted photons, particularly in amorphous materials. This noise limits their utility, as heralding detectors cannot distinguish between genuine pairs produced by the source and unpaired single photons. In this thesis we propose and theoretically analyse a new photon generation method we term "Stimulated Spontaneous Three Photon Down Conversion". Pumping a nonlinear material at the third harmonic, we spontaneously generate three photons at the fundamental frequency - spectrally isolated from the Raman noise around the pump. A weak seed beam near the fundamental frquency leads to an increase in the rate of correlated pairs produced on either side of the seed, resulting in an effective heralded single-photon source of much reduced noise. We work in the framework of a fully multi-mode Hamiltonian formalism of nonlinear quantum optics. Applying this technique in fused silica microfibre could in principle produce 0.03 pairs per pulse, with realistic pump field requirements.