Just as the internet relies on routers to ensure that packets of data reach their intended recipients, quantum information networks will need switches that can direct the flow of quantum bits between nodes. In networks linked by photons—say, communication networks that use photons to transmit quantum encrypted data or parallel computing schemes that use them to link individual quantum processors—switches must manipulate photons’ trajectories without destroying the information they carry. (See the article by Michael Raymer and Kartik Srinivasan, Physics Today, November 2012, page 32.) A new device developed by Barak Dayan and coworkers at the Weizmann Institute of Science in Rehovot, Israel, may do the job.1
In the researchers’ scheme, illustrated in the figure, a rubidium atom coupled with a microsphere optical resonator directs the traffic of photons along an optical fiber connecting two input and two output ports: The switch routes incoming photons to...
