R&D: On-Demand Multimode Optical Storage in Laser-Written On-Chip Waveguide

Physical Review A has published an article written by Ming-Xu Su, Tian-Xiang Zhu, Chao Liu, Zong-Quan Zhou, Chuan-Feng Li, and Guang-Can Guo, CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China; CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China and Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China.

Abstract: “Quantum memory is a fundamental building block for large-scale quantum networks. On-demand optical storage with a large bandwidth, a high multimode capacity, and an integrated structure simultaneously is crucial for practical application. However, this has not been demonstrated yet. Here, we fabricate an on-chip waveguide in a $151\mathrm{Eu}3+:Y_2{\mathrm{SiO}}_5$ crystal with insertion losses of 0.2 dB, and propose a pumping scheme to enable spin-wave atomic frequency comb (AFC) storage with a bandwidth of 11 MHz inside the waveguide. Based on this, we demonstrate the storage of 200 temporal modes using the AFC scheme and conditional on-demand storage of 100 temporal modes using the spin-wave AFC scheme. The interference visibility between the readout light field and the reference light field is $99.0\%\pm 0.6\%$ and $97\%\pm 3\%$ for AFC and spin-wave AFC storage, respectively, indicating the coherent nature of this low-loss, multimode, and integrated storage device.“