标题： 多模自由空间延迟干涉仪，无需折射补偿元件用于相位编码QKD协议 显示英文标题

标题： Multi-mode free-space delay interferometer with no refractive compensation elements for phase encoded QKD protocols

摘要： 我们展示了无需补偿的多模延迟干涉仪实现方法，主要用于相位编码量子密钥分发（QKD）。 通过适当选择光束的横向尺寸，在不平衡的迈克尔逊或马赫-曾德干涉仪中实现了具有相对宽延迟范围的空间多模光束的高干涉可见度。 我们提供了一个简单的理论模型，该模型直接连接了干涉可见度、延迟和光束参数之间的关系。 所进行的实验研究验证了我们的理论发现，并且测量出了高达0.95的2纳秒延迟下的可见度。 由于其简单性和稳健性能，我们的方法成为在量子信号通过多模光纤接收的QKD系统中的实用选择。 这种配置的重要应用是一个跨模式QKD系统，其中自由空间大气通信通道耦合到多模光纤的一段中，以最小的耦合损耗将空间畸变的光束传输到远程接收器。 显示英文摘要

摘要： We demonstrate compensation-free approach to the realization of multi-mode delay interferometers, mainly for use in phase encoded quantum key distribution (QKD). High interference visibility of spatially multimode beams in unbalanced Michelson or Mach-Zehnder interferometers with a relatively wide range of delays is achieved by the appropriate choice of the transverse size of the beam. We provide a simple theoretical model that gives a direct connection between the visibility of interference, the delay, and the beam parameters. The performed experimental study confirms our theoretical findings and demonstrates the measured visibility of up to 0.95 for the delay of 2 ns. Our approach's simplicity and robust performance make it a practical choice for the implementation of QKD systems, where a quantum signal is received over a multimode fiber. The important application of such configuration is an intermodal QKD system, where the free-space atmospheric communication channel is coupled into a span of the multimode fiber, delivering the spatially distorted beam to the remote receiver with minimal coupling loss.