Research in Optical Sciences
Revival of Silenced Echo for Optical Quantum Memories: Efficiency and Noise Level
M Bonarota, Vianney Damon, T. Chanelière, Jean-Louis Le Gouët, M. F. Pascual Winter
Abstract
We present a novel quantum memory protocol inspired by the two photon echo that overcomes the main drawbacks of the latter, namely, contamination of the retrieval pulse by spontaneous emission and free induction decay. It makes use of two rephasing pulses instead of one, the second is intended to send the atoms back to the fundamental state so that the echo is emitted in a non-inverted medium. The emission of the echo after the first pulse is prevented by unfulfillment of the spatial phase matching condition. Experimental maximum efficiency is found to be limited to 30% for 0:5 at. % Tm3+:YAG, mainly because of finite coherence lifetime. We have performed a preliminary analysis of noise, finding a significant reduction of spontaneous emission noise in the retrieval mode. However, further improvements are to be done since the signal to noise ratio is still close to one.