Opt Express. 2022 Dec 5;30(25):44365-44374. doi: 10.1364/OE.470364.
Free-space quantum key distribution (QKD) has been gaining popularity in recent years due to its advantages in creating networking options for the quantum internet. One of the main challenges to be addressed in QKD is the achievable secret key rate, which must meet current and future demand. Some of the existing solutions include the use of higher bandwidth electronics, untrusted relay architectures such as Twin-Field QKD, or high dimensional QKD. In this work, we proposed the use of a combination of spatial-multiplexing and time-division techniques, together with the use of 2D single-photon avalanche diode arrays to increase the final throughput. The main challenge in a free-space scenario is the effects introduced by turbulence. This paper demonstrates how appropriate time-division of the spatial-modes can reduce the quantum bit error rate due to optical crosstalk from 36% to 0%. With this technique, we believe the future need for superconducting nanowires single photon detectors, in some free-space QKD applications, can be relaxed, obtaining more cost-effective receiver systems.
自由空间量子密钥分发（QKD）近年来因其在为量子互联网创建网络选项方面的优势而受到关注。QKD 中需要解决的主要挑战之一是可实现的密钥速率，该速率必须满足当前和未来的需求。一些现有的解决方案包括使用更高带宽的电子设备、不可信中继架构（如 Twin-Field QKD）或高维 QKD。在这项工作中，我们提出了使用空间复用和时分技术的组合，以及使用二维单光子雪崩二极管阵列来提高最终的吞吐量。自由空间场景中的主要挑战是由湍流引起的影响。本文演示了如何适当的时分空间模式可以将由于光学串扰引起的量子误码率从 36%降低到 0%。通过这项技术，我们相信在一些自由空间 QKD 应用中，对超导纳米线单光子探测器的未来需求可以得到缓解，从而获得更具成本效益的接收系统。
