Efficient and long-lived quantum memory with cold atoms inside a ring cavity

Date: 2012-05-20
Authors Xiao-Hui Bao, Andreas Reingruber, Peter Dietrich, Jun Rui, Alexander Dück, Thorsten Strassel, Li Li, Nai-Le Liu, Bo Zhao and Jian-Wei Pan
Journal No. Nature Physics 8, 517 (2012)
Abstract Quantum memories are regarded as one of the fundamental building blocks of linear-optical quantum computation and long-distance quantum communication. A long-standing goal to realize scalable quantum information processing is to build a long-lived and efficient quantum memory. There have been significant efforts distributed towards this goal. However, either efficient but short-lived or long-lived but inefficient quantum memories have been demonstrated so far. Here we report a high-performance quantum memory in which long lifetime and high retrieva l efficiency meet for the first time. By placing a ring cavity around an atomic ensemble, employing a pair of clock states, creating a long-wavelength spin wave and arranging the set-up in the gravitational direction, we realize a quantum memory with an intrinsic spin wave to photon conversion efficiency of 73(2)% together with a storage lifetime of 3.2(1) ms. This realization provides an essential tool towards scalable linear-optical quantum information processing.