Tailored photon pair preparation relying on full group velocity matching   in fibre-based spontaneous four wave mixing
  We study photon pair generation through scalar spontaneous four-wave mixing in single-mode fibre and for frequency-degenerate pumps; we concentrate on source geometries which fulfil full group velocity matching (GVM), i.e. where the pump, signal and idler propagate at identical group velocities. We discuss two experimental techniques which permit the attainment of full GVM, and discuss the resulting two-photon state properties. In particular, we show that full GVM can lead to sources which approach phasematching unconstrained by dispersion and therefore with a remarkably large bandwidth. We also discuss the generation of nearly-factorablestates as an application of full GVM. 
Karina Garay-Palmett, Ra\'ul Rangel-Rojo, Alfred B. U'Ren