Park Jiho, Kim Heonoh, Seb Moon Han
Opt Lett. 2020 Apr 15;45(8):2403-2406. doi: 10.1364/OL.388613.
Entanglement swapping forms a key concept in the realization of scalable quantum networks and large-scale quantum communication. For the practical implementation of entanglement swapping, completely autonomous entanglement sources and a joint Bell-state measurement (BSM) between two independent photons are essential. Here, we experimentally demonstrate entanglement swapping between two independent polarization-entangled photon-pair sources obtained via spontaneous four-wave mixing (SFWM) in a Doppler-broadened atomic ensemble of ${^{87}}{\rm Rb}$Rb atoms. From the joint BSM, we estimate the ${\rm S}$S parameter in the Clauser-Horne-Shimony-Holt (CHSH) form of Bell's inequality and confirm the violation of the Bell-CHSH inequality by ${\rm S}={2.32} \pm {0.07}$S=2.32±0.07 with 4.5 standard deviations. We believe that this work is an important step toward realizing practical scalable quantum networks.
纠缠交换是实现可扩展量子网络和大规模量子通信的关键概念。对于纠缠交换的实际实现，完全自主的纠缠源以及两个独立光子之间的联合贝尔态测量（BSM）至关重要。在此，我们通过实验证明了在多普勒展宽的 ${^{87}}{\rm Rb}$ 铷原子系综中，通过自发四波混频（SFWM）获得的两个独立偏振纠缠光子对源之间的纠缠交换。通过联合 BSM，我们在贝尔不等式的克劳泽 - 霍恩 - 希莫尼 - 霍尔特（CHSH）形式中估计了 ${\rm S}$ 参数，并确认贝尔 - CHSH 不等式被违反，其中 ${\rm S}={2.32} \pm {0.07}$，偏差为 4.5 个标准差。我们相信这项工作是朝着实现实用的可扩展量子网络迈出的重要一步。
