Fig. 1
From: High-performance Raman quantum memory with optimal control in room temperature atoms
Raman memory. a Schematic, atomic energy levels and frequencies of the optical fields. |g, m〉: hyperfine levels |52S1/2, F = 1, 2〉; |e1〉 and |e2〉: excited states |52P1/2, F = 2〉 and |52P3/2〉. W write field, Ein input signal, Eleak leaked signal, SW collective atomic spin wave, R read field, ER retrieved signal. b Experimental setup. The polarizations of the weak signal beams, Ein and ER, are perpendicular to the strong driving beams, W and R. The signals can be detected by homodyne detection. OP optical pumping laser, SMF single-mode fiber, BS beam splitter, PZT piezoelectric transducer. D1 photo-detector, D2 and D3 photo-diode, D4 single-photon detector, FM1 and FM2 flip mirror. The flip mirrors FM1,2 allow alternative selection of detections via intensity, homodyne, and single photon. Intensity detection is chosen to calibrate the memory efficiency by flipping FM1 up, homodyne detection combining with tomography reconstruction to determine the memory fidelity by flipping FM1 down and FM2 up, and single-photon detection to measure and analyze the excess noise in storage process by flipping FM1,2 both down
