Tunable photon-ion entanglement enables quantum networks Nature | Innsbruck In Nature 485 and concurrent KurzweilAI press coverage, Rainer BlattTracy Northup, and Andreas Stute have constructed an interface for quantum networks that is both efficient and freely tunable—the first interface between a single ion and a single photon. "Whenever we have to transfer quantum information from processing sites to communication channels, and vice versa, we’re going to need an interface between light and matter," explains Northup. "This technique has two significant advantages over previous approaches that have entangled atoms with light: the efficiency with which we produce entangled photons is quite high and in principle could be increased to over 99 percent. But above all, this setup allows us to generate any possible entangled state.”