Hu Xiao-Min, Huang Cen-Xiao, Sheng Yu-Bo, Zhou Lan, Liu Bi-Heng, Guo Yu, Zhang Chao, Xing Wen-Bo, Huang Yun-Feng, Li Chuan-Feng, Guo Guang-Can
CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, People's Republic of China.
CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China.
Phys Rev Lett. 2021 Jan 8;126(1):010503. doi: 10.1103/PhysRevLett.126.010503.
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 tabletop. Here we propose and report a high-efficiency and long-distance entanglement purification using only one pair of hyperentangled state. 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 inequality of polarization entanglement arises from 1.829 to 2.128. Moreover, by using one pair of hyperentanglement and deterministic controlled-NOT gates, the total purification efficiency can be estimated as 6.6×10^{3} times than the experiment using two pairs of entangled states with spontaneous parametric down-conversion sources. Our results offer the potential to be implemented as part of a full quantum repeater and large-scale quantum network.
高质量的长距离纠缠对于量子通信和可扩展量子网络都至关重要。纠缠纯化是在噪声环境中从低质量纠缠中提取高质量纠缠，它在量子中继器中起着关键作用。先前的重要纠缠纯化实验需要两对低质量纠缠态，并且是在桌面实验中进行演示的。在此，我们提出并报告了一种仅使用一对超纠缠态的高效长距离纠缠纯化方法。我们还展示了其在基于纠缠的量子密钥分发（QKD）中的实际应用。一对偏振空间模式超纠缠在11公里的多芯光纤（噪声信道）中进行了分发。纯化后，偏振纠缠的保真度从0.771提高到0.887，基于纠缠的QKD中的有效密钥率从0增加到0.332。偏振纠缠的克劳泽 - 霍恩 - 希莫尼 - 霍尔特不等式的值从1.829增加到2.128。此外，通过使用一对超纠缠和确定性受控非门，总纯化效率估计比使用两对具有自发参量下转换源的纠缠态进行的实验高6.6×10³倍。我们的结果为作为完整量子中继器和大规模量子网络的一部分得以实现提供了可能性。
