Generation of fiber-coupled, nondegenerate, polarization-entangled photons for quantum communication

Abstract

The production of polarization-entangled photon pairs from spontaneous parametric downconversion (SPDC) enables many applications of quantum information processing. In this thesis, we use type-0 phase-matched downconversion of pump photons from a 532 nm continuous-wave laser to generate 798 nm signal and 1.6 tim idler photon pairs in periodically-poled, congruent lithium niobate (PPLN). Difference frequency generation of 798 nm is used for characterizing PPLN, including phase matching bandwidth and effective nonlinear coefficient. Optimal focusing for generating a single spatial mode SPDC output allows efficient coupling of signal and idler photons. Through coincidence counting, our source's spectral brightness is measured to be 3.6 x 105 Hz/mW/nm detected pairs/s/mW of pump power per nm of output photon bandwidth with an idler conditional detection efficiency of 1.6%. This work is a significant first step toward realizing a high-flux source of nondegenerate polarization-entangled photons.