An efficient quantum light–matter interface with sub-second lifetime

An efficient light–matter interface for quantum repeaters is developed. By placing Rb atoms optically confined in a 3D lattice in a ring cavity, an initial retrieval efficiency of 76% together with a 1/e lifetime of 0.22 s are achieved. Quantum repeaters 1 hold promise for scalable long-distance quantum communication. The basic building block is a quantum light–matter interface that generates non-classical correlations between light and a quantum memory 2 . Significant progress has been made in improving the performance of this interface 3 , 4 , but further development of quantum repeater is hindered by the difficulty of integrating the key capabilities into a single system 4 . Here we report a high-performance interface with an efficiency and lifetime that fulfil the requirement of a quantum repeater. By confining cold atoms with a three-dimensional optical lattice and enhancing the atom–photon coupling with a ring cavity, we observe an initial retrieval efficiency of 76 ± 5% together with a 1/ e lifetime of 0.22 ± 0.01 s, which supports a sub-Hz entanglement distribution of up to 1,000 km through the Duan-Lukin-Cirac-Zoller (DLCZ) protocol 2 . Together with an efficient telecom interface 5 , 6 and moderate multiplexing 7 , our result may enable a quantum repeater system that beats direct transmission in the near future 4 .