How filtering affects photon-pairs produced by parametric processes
Daniel R. Blay, Michael J. Steel, L. G. Helt · 2017
Many quantum information protocols require the high rate production of individual photons with near unit purity. The most mature platform for producing these photons is nonlinear optical sources, which exploit parametric processes to produce photon pairs, one of which is subsequently detected to “herald” the presence of its partner. The photon pairs produced in such sources often have strong frequency correlations, which adversely affect the purity of the heralded single photons, and so such sources are spectrally filtered to restore the purity. Because this process throws away photons, the rate of photon production is reduced - filtering increases purity at the cost of efficiency. This relationship has been explored extensively numerically [1-3], but has not been well understood analytically. As the demand for multi-photon experiments increases, it is becoming necessary to precisely quantify the trade-off between purity and efficiency. We believe our work enables this.