An entangled-LED-driven quantum relay over 1 km

A quantum relay harnessing coupled photons from a light-emitting diode removes the need for insecure routing nodes in quantum cryptography. The device developed by Mark Stevenson from Toshiba Research Europe Limited and his colleagues creates photons that are entangled; that is, they share quantum properties even when they are far apart. These two photons, when divided between the sender and receiver of a message, enable a security key to be safely shared. Sending optical signals over long distances usually requires additional systems called nodes to boost the signal or split it to multiple receivers. Such nodes pose a security risk as they could be used by an eavesdropper to intercept the message. The electrically driven quantum relay circumvents this security risk and enables communication over a one kilometer optical fiber.