Long-distance entanglement purification for quantum communication

• Published in: arXiv.org
• Main Authors: Xiao-Min, Hu, Cen-Xiao, Huang, Yu-Bo, Sheng, Zhou, Lan, Bi-Heng, Liu, Guo, Yu, Zhang, Chao, Wen-Bo, Xing, Yun-Feng, Huang, Chuan-Feng, Li, Guo, Guang-Can
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 20.01.2021
• Subjects: Entangled states; Physics - Quantum Physics; Polarization; Purification; Quantum cryptography; Quantum entanglement; Repeaters
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2101.07441

High-quality long-distance entanglement is essential for both quantum communication and scalable quantum networks. Entanglement purification is to distill high-quality entanglement from low-quality entanglement in a noisy environment and it plays a key role in quantum repeaters. The previous significant entanglement purification experiments require two pairs of low-quality entangled states and were demonstrated in table-top. Here we propose and report a high-efficiency and long-distance entanglement purification using only one pair of hyperentangled states. We also demonstrate its practical application in entanglement-based quantum key distribution (QKD). One pair of polarization spatial-mode hyperentanglement was distributed over 11 km multicore fiber (noisy channel). After purification, the fidelity of polarization entanglement arises from 0.771 to 0.887 and the effective key rate in entanglement-based QKD increases from 0 to 0.332. The values of Clauser-Horne-Shimony-Holt (CHSH) inequality of polarization entanglement arises from 1.829 to 2.128. Moreover, by using one pair of hyperentanglement and deterministic controlled-NOT gate, the total purification efficiency can be estimated as 6.6x10^3 times than the experiment using two pairs of entangled states with spontaneous parametric down-conversion (SPDC) sources. Our results offer the potential to be implemented as part of a full quantum repeater and large scale quantum network.