A high-fidelity single-photon source based on a type-II optical   parametric oscillator
  Using a continuous-wave type-II optical parametric oscillator below threshold, we have demonstrated a novel source of heralded single-photons with high-fidelity. The generated state is characterized by homodyne detection and exhibits a 79% fidelity with a single-photon Fock state (91% after correction of detection loss). The low admixture of vacuum and the well-defined spatiotemporal mode are critical requirements for their subsequent use in quantum information processing. 
Olivier Morin (LKB - Jussieu), Virginia D'Auria (LPMC), Claude Fabre   (LKB - Jussieu), Julien Laurat (LKB - Jussieu)
quant-ph