The team lead by PAN Jianwei and BAO Xiaohui from University of Science and Technology of China has developed a high-performance light-matter interface, which fulfills a quantum repeater with both an efficiency and a lifetime for the first time. This work will have significant applications in the long-distance quantum communication in the near future.
Quantum communication is the art of transferring a quantum state from one place to another. It holds ultra-high security as a quantum photon can neither be separated nor duplicated. Direct transmission is limited to moderate distances (less than 500 km) due to the exponential decay of photons and the solution could be the quantum repeater. The quantum repeater, as the amplifier stations, will extend the communication range by amplify the light signals. One attractive strategy for realizing quantum repeaters is based on the use of atomic ensembles as quantum memories.
Recently, significant progress has been made in improving the performances of quantum memories. However, further advances are hindered by the difficulty of integrating key capabilities such as long storage times and high memory efficiency into a single system. A cold atomic-ensemble quantum memory is proved to be important for its simpler realization and greatly improved generation efficiency. In 2012, PAN's team has presented an efficient quantum memory with mm-second lifetime, which is a factor of 10000 times higher than the duration of pulsed optical operations [Nature Physics 8, 517–521 (2012)].
In order to improve to duration to realize long-distance transmission, PAN's team uses a three-dimensional (3D) optical lattice to confine an atomic ensemble inside a ring cavity. This time they achieve a lifetime of 0.22 second and the initial retrieval efficiency is 76% in the mean time. The total efficiency has been promoted by two orders of magnitude.
This work will help to realize quantum communication to distance of more than 500 km and even 1000 km in some situation. For the first time, scientists improve both long storage times and high memory efficiency. The referee highlights this work as "extraordinary tour de force".
This work was published in Nature Photonics in this April with the title "An efficient quantum light–matter interface with sub-second lifetime".
The research is supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences, and the National Fundamental Research Program of China.
(HUANG Xingxing, USTC News Center)
Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics,
University of Science and Technology of China,
Hefei, Anhui 230026, China.