Upconversion as a tool for characterization and preparationof photonic quantum states

摘要

The process of upconversion in a nonlinear crystal involves the annihilation of two photons and the generation of a single photon with frequency given by the sum of the incident photon frequencies. In this paper we discuss recent work where we exploit the upconversion of two photonic modes, each of them generated by the process of spontaneous parametric downconversion, either from the same or different crystals. On the one hand, we describe an experiment where we exploit upconversion for the temporal characterization of photon pairs. On the other hand, we describe an experimental technique, which relies on the detection of an upconverted photon from two distinct photon-pair sources, which permits two photons that never interacted to become entangled in frequency.