Towards a down-conversion source of positively spectrally correlated and decorrelated photon pairs at telecom wavelength

Summary form only given. The frequency correlation (or decorrelation) of photon pairs is of great importance in long-range quantum communications and photonic quantum computing. We experimentally characterize a spontaneous parametric down conversion (SPDC) source, based on a β-Barium Borate (BBO) crystal cut for type-II phase matching at 1550 nm which has the capability to emit photons with positive or no spectral correlations. Our system, depicted in Fig. 1a), employs a carefully designed detection method exploiting two InGaAs detectors.In the process of SPDC the joint effect of the nonlinear crystal and the collection optics can be described using an effective phase matching function [2,3]. Its diagonal slices can be accessed by measuring the joint spectral amplitudes for a range of CW pump laser settings. For that we measured the relative detection time statistics of photons traveling through two long fibers and exploit the dispersion experienced in single mode fiber [1]. The measurement results are depicted in Fig. 1b) and agree well with the theoretical model presented in Ref. [2]. The EPMF in this configuration suitable for generating positively-correlated or uncorrelated photon pairs without using spectral filtering when pumped using broadband pulses. This measurement was only possible because of the improved sensitivity of our fiber spectrometer, which was achieved by using a combination of free-running and gated InGaAs detectors.