Generating triggered entangled photons with a semiconductor source

The generation of entangled photon pairs is a fundamental cornerstone of quantum optics, and an essential technology in the high profile field of quantum communication and computing. Currently the most widely used techniques for generating entangled photon pairs are nonlinear optical processes, such as parametric down conversion, which produce a probabilistic number of pairs per excitation cycle. Such a source is of limited use in quantum information/processing applications where a regular stream of single entangled photon pairs is usually required. We have produced such a triggered source from a semiconductor device for the first time, using a two-photon cascade in a single quantum dots, demonstrating efficiencies up to 70%, close to the level required for useful applications. Single quantum dots could prove to be the first robust and compact triggered source of entangled photons