Figure 1: Experimental setup for demonstration of a multiplexed quantum memory with 225 memory cells.

(a) The write and the read laser beams are directed by the multiplexing AODs to address 15 × 15 atomic memory cells contained in single macroscopic atomic ensemble, with the distance between neighboring cells of 126 μm. For clarity, only 3 × 5 cells are shown in the figure. Write-in/read-out of quantum information to/from the memory cell is achieved through the DLCZ scheme. The signal and the idler photons emitted by the memory cells from different paths are combined by the de-multiplexing AODs into the same single-mode fiber for detection with a single-photon counting module (SPCM). The polarization of the write/read beam from a single mode fiber is adjusted by a quarter-wave plate (QWP) and a half-wave plate (HWP) to generate the highest first-order diffraction efficiency from the AOD. For each beam, a pair of crossed AODs in orthogonal directions X and Y are used to scan the angle of deflected beam in the corresponding directions. The lens are used to map different angles of the deflected beams to different positions at the atomic ensemble as well as to focus the beams. A Fabry-Perot cavity (etalon) is inserted in the path of the signal/idler mode to further filter our the strong write/read beam by frequency selection. (b) Zoom-in of the beam configuration at two memory cells denoted as L and R. (c) The relevant level diagram of ⁸⁷Rb atoms for the write and read process, with , , and . The detuning of the write beam is at Δ=10 MHz.