• Photonics Research
  • Vol. 9, Issue 10, 10001998 (2021)
Yi-Chen Liu1、†, Dong-Jie Guo1、†, Ran Yang1, Chang-Wei Sun1, Jia-Chen Duan1, Yan-Xiao Gong1、2、*, Zhenda Xie1、3、*, and Shi-Ning Zhu1
Author Affiliations
  • 1National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
  • 2e-mail: gongyanxiao@nju.edu.cn
  • 3e-mail: xiezhenda@nju.edu.cn
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    Narrowband photonic entanglement is a crucial resource for long-distance quantum communication and quantum information processing, including quantum memories. We demonstrate the first polarization entanglement with 7.1 GHz inherent bandwidth by counterpropagating domain engineering, which is also confirmed by Hong–Ou–Mandel interference with 155-ps base-to-base dip width and (97.1±0.59)% high visibility. The entanglement is harnessed with 18.5-standard-deviations Bell inequality violation, and further characterized with state tomography of (95.71±0.61)% fidelity. Such narrowband entanglement sets a cornerstone for practical quantum information applications.

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