Fig. 2: Building a multiplexed quantum repeater node with 280 modes.
a The detailed experimental setup. We combine 70 spatial and 4 angular dimensions into a total of 280 time-bin modes. Here each combination of the spatial and angular modes can be individually addressed by the 2D AOD system with the help of AOMs (acoustic-optical modulators) and EOMs (electrical-optical modulators). The signal mode at 795 nm is converted to 1546 nm on a PPLN (Periodically poled lithium niobate) waveguide. SPD represents a single-photon detector. b The corresponding AOD frequencies for each memory cell. c, d The performance of the memory array. We choose 3 memory modes with each locating at different representative regions of the memory array and emitting at different emission angles (the orange circle represents the memory mode with fx = 103 MHz, fy = 103 MHz, emission angle in A direction as shown in a, b; the blue triangle and the purple diamond represents (106, 97, B) and (115, 91, C), respectively), and demonstrate corresponding retrieval efficiency (including all losses) and cross-correlation \({g}_{s,i}=\frac{{p}_{s,i}}{{p}_{s}{p}_{i}}\) in each mode with varying storage time. The corresponding storage time of the three modes are 227 ± 21 μs, 261 ± 22 μs, and 190 ± 22 μs, respectively. e The performance of wavelength conversion. The device efficiency (circle) of the PPLN waveguide and the noise counts received by the detector (triangle) are measured under different pumping powers. The highest device efficiency is ~45% with a pumping laser ~1 W, and the end-to-end efficiency is about 12% due to multiple stages of filtering and fiber connections. Error bars represent one standard deviation in this figure.
