Researchers from the Weizmann Institute in Israel have demonstrated the first photonic router, which is a quantum device based on a single atom that enables routing of single photons. At the core of the device is an atom that can switch between two states. The state is set just by sending a photon from the right or the left via an optical fiber. In response, the atom reflects or transmits the next incoming photon.In one state, a photon coming from the right continues on its path to the left, whereas a photon coming from the left is reflected backwards, which causes the atomic state to flip. In this reversed state, the atom lets photons coming from the left continue in the same direction, while any photon coming from the right is reflected backwards. The router makes use of laser cooling and chip-based miniature optical resonators.
Source: Weizmann Institute