自由空间和光纤混合信道量子密钥分配技术研究

To meet the need of the worldwide space-ground integrated quantum secure communication networks, this project on quantum key distribution problems over free space and optical fiber hybrid channels, based on the research results of quantum key distribution over only free space channels or optical fiber channels and combined with the transmission and retention characteristics of photon quantum states over free space and optical fiber quantum channels, carries out the research on schemes, protocols and encoding technologies of quantum key distribution over free space and optical fiber hybrid channels. This project aims to propose a quantum key distribution scheme which is suitable for transmitting over free space and optical fiber hybrid channels, break through the key technologies of the conversion of between the polarization encoding and phase encoding, develop the converter, build a hybrid channel quantum key distribution demonstration prototype, verify correctness and reasonableness of the quantum key distribution scheme over free space and optical fiber hybrid channels, and provide a feasible approach for the worldwide space-ground integrated quantum secure communication networks.

针对天地一体化广域量子保密通信组网需求，本项目拟以自由空间和光纤混合信道量子密钥分配问题为研究对象，在自由空间或光纤单一信道量子密钥分配研究成果的基础上，结合自由空间量子信道和光纤量子信道对光量子态的传输和保持特性，开展混合信道量子密钥分配方案、协议和编码技术研究。通过本项目研究，旨在提出一种适合混合信道传输的量子密钥分配方案，突破偏振编码和相位编码转换等关键技术，研制偏振和相位编码转换器，搭建混合信道量子密钥分配演示样机，验证自由空间和光纤混合信道量子密钥分配方案的正确性与合理性，为实现天地一体化广域量子保密通信网络提供一种可行的技术途径。

本项目面向天地一体化广域量子保密通信组网需求，针对自由空间和光纤混合信道量子密钥分发开展了研究，通过分析自由空间量子信道和光纤量子信道对量子态的传输和保持特性，提出了基于偏振-相位纠缠的混合信道量子密钥分发方案。方案的关键在于光量子在跨越不同信道时的编码转换技术，我们提出了偏振-相位纠缠编码转换方案，设计了基于两个并联的Mach-Zehnder干涉环的实现方案，仿真分析了干涉环对比度影响因素，有效指导了干涉环的制作，进一步研制了编码转换模块，测试了两个Mach-Zehnder的插入损耗，分别为4.33dB和4.91dB，两个干涉环的臂长差均为4965.9mm，误差小于1mm，对应延时为24.32ns。进一步，搭建了一套单光子混合信道传输测试系统，对水平偏振态和垂直偏振态分别测试了转换为相位态后相应的干涉环干涉对比度，干涉对比度均达到98%，完成了自由空间和光纤混合信道的编码转换功能验证。为我国构建天地一体化广域量子网络提供了一种星地互联的量子通信技术方案。

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