Experimental demonstration of a heralded entanglement source

Date: 2010-05-30
Authors Claudia Wagenknecht, Che-Ming Li, Andreas Reingruber, Xiao-Hui Bao, Alexander Goebel, Yu-Ao Chen, Qiang Zhang, Kai Chen and Jian-Wei Pan
Journal No. Nature Photonics 4, 549 (2010)
Abstract The heralded generation of entangled states is a long-standing goal in quantum information processing, because it is indispensable for a number of quantum protocols1,2. Polarization entangled photon pairs are usually generated through spontaneous parametric down-conversion3, but the emission is probabilistic. Their applications are generally accompanied by post-selection and destructive photon detection. Here, we report a source of entanglement generated in an event-ready manner by conditioned detection of auxiliary photons4. This scheme benefits from the stable and robust properties of spontaneous parametric down-conversion and requires only modest experimental efforts. It is flexible and allows the preparation efficiency to be significantly improved by using beamsplitters with different transmission ratios. We have achieved a fidelity better than 87% and a state preparation efficiency of 45% for the source. This could offer promise in essential photonics-based quantum information tasks, and particularly in enabling optical quantum computing by reducing dramatically the computational overhead5,6.