Diggester tips news that physicists from Tsinghua University in China have published "the first proof-of-principle demonstration of a genuine quantum router
." The group's paper
(PDF) is available at the arXiv. MIT's Technology Review describes it thus:
"In this new device, the information is encoded in the polarization of photons, either horizontal or vertical. The Chinese group begin by creating a single photon that is in a superposition of both horizontal and vertical polarization states. They then convert this single photon into a pair of lower energy photons that are entangled, a process called parametric down conversion. Both of these photons are also in a superposition of polarization states. The router works by using the polarization of one of these photons as the control signal to determine the route of the other, the data signal. The device is simple, little more than a collection of half mirrors for guiding photons and waveplates for rotating their polarization."