We present a light-storage experiment in a praseodymium-doped crystal where the light is mapped onto an inhomogeneously broadened optical transition shaped into an atomic frequency comb. After absorption of the light the optical excitation is converted into a spin-wave excitation by a control pulse. A second control pulse reads the memory (on-demand) by reconverting the spin-wave excitation to an optical one, where the comb structure causes a photon-echo type rephasing of the dipole moments and directional retrieval of the light. This combination of photon echo and spin-wave storage allows us to store sub-microsecond (450ns) pulses for up to 20 microseconds. The scheme has a high potential for storing multiple temporal modes in the single photon regime, which is an important resource for future long-distance quantum communication based on quantum repeaters.
@article{arxiv.0908.2309,
title = {Demonstration of atomic frequency comb memory for light with spin-wave storage},
author = {Mikael Afzelius and Imam Usmani and Atia Amari and Björn Lauritzen and Andreas Walther and Christoph Simon and Nicolas Sangouard and Jiří Minář and Hugues de Riedmatten and Nicolas Gisin and Stefan Kröll},
journal= {arXiv preprint arXiv:0908.2309},
year = {2010}
}