Ultracompact, space-suitable, and hybrid entangled photon source for satellite-based QKD

Within the EU-funded consortium QuDice technologies and systems for space-based Entanglement distributions are developed, amongst them also a compact and space-suitable entangled photon source. The source’s architecture is based on a high-performant linear Mach-Zehnder Interferometer in a beam-displacer configuration, using a ppKTP nonlinear material for spontaneous-parametric down-conversion to the C-Band. The source will be tested by means of thermal vacuum and mechanical vibration cycling. Its performance on the laboratory level proved 800..900k counts/s/mW for Signal and Idler and 300k coincidences, an overall heralding efficiency of >33% and visibilities >98%. The form factor of the Engineering Qualification Model fits into a volume of ca. 100x80x50 mm3, excluding the pump laser and electronics for the nonlinear material temperature levelling.