Shi Shuai, Dong Ming-Xin, Yu Yi-Chen, Ye Ying-Hao, Zhang Wei, Wang Kai, Guo Guang-Can, Ding Dong-Sheng, Shi Bao-Sen
Opt Express. 2020 Apr 13;28(8):11538-11547. doi: 10.1364/OE.383378.
High-dimensional entangled states and quantum repeaters are important elements in efficient long-range quantum communications. The high-dimensional property associated with the orbital angular momentum (OAM) of each photon improves the bandwidth of the quantum communication network. However, the generation of high-dimensional entangled states by the concentration method reduces the brightness of the entangled light source, making extensions to these higher dimensions difficult. To overcome this difficulty, we propose to generate entangled qutrits in the OAM space by loading the pump light with OAM. Compared with the concentration method, our experimental results show that the rate of generation of photon pairs improves significantly with an observed 5.5-fold increase. The increased generation rate provides the system with the ability to resist the noise and improve the fidelity of the state. The S value of the Clauser-Horne-Shimony-Holt inequality increases from 2.48 ± 0.07 to 2.69 ± 0.04 under the same background noise, and the fidelity of the reconstructed density matrix improves from 57.8 ± 0.14% to 70 ± 0.17%. These achievements exhibit the enormous advantages of high-dimensional entanglement generation.
高维纠缠态和量子中继器是高效远程量子通信的重要元素。与每个光子的轨道角动量（OAM）相关的高维特性提高了量子通信网络的带宽。然而，通过浓缩方法生成高维纠缠态会降低纠缠光源的亮度，使得向这些更高维度的扩展变得困难。为了克服这一困难，我们提议通过给泵浦光加载OAM在OAM空间中生成纠缠三量子比特。与浓缩方法相比，我们的实验结果表明，光子对的生成速率显著提高，观察到增加了5.5倍。增加的生成速率使系统具有抵抗噪声和提高态保真度的能力。在相同背景噪声下，Clauser-Horne-Shimony-Holt不等式的S值从2.48±0.07增加到2.69±0.04，重构密度矩阵的保真度从57.8±0.14%提高到70±0.17%。这些成果展现了高维纠缠生成的巨大优势。
