A telecom-wavelength quantum repeater node based on a trapped-ion processor

A quantum repeater node is presented based on trapped ions that act as single photon emitters, quantum memories and an elementary quantum processor. The node's ability to establish entanglement across two 25 km-long optical fibers independently, then to swap that entanglement efficiently to extend it over both fibers, is demonstrated. The resultant entanglement is established between telecom-wavelength photons at either end of the 50 km channel. The system improvements to allow for repeater-node chains to establish stored entanglement over 800 km at Hertz rates are calculated, revealing a near-term path to distributed networks of entangled sensors, atomic clocks and quantum processors.