Abstract

Entangled photon pairs have become an important tool in experiments on the foundations of quantum mechanics and for the new field of quantum information. The most common way to create such photons at wavelengths in the red or near-infrared region is spontaneous parametric down- conversion (SPDC). Yet, most of the experiments and potential applications suffer from the low yield of the fluorescence process. We report on a method to optimize collection efficiency by matching the angular distribution of the parametric fluorescence to the spatial mode of an optical fiber. With this technique, we detected 360000 polarization-entangled photon pairs per second in the near-IR region in single-mode optical fibers (fig. 1a) with a large frame Ar-ion laser as the pump source (P = 460 mW) of a nonlinear crystal. The entanglement of the photon pairs was verified by measuring polarization correlations of at least 96% in a H/V- and in a ±45°-basis [1].

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