Carrasco-Casado Alberto, Kunimori Hiroo, Takenaka Hideki, Kubo-Oka Toshihiro, Akioka Maki, Fuse Tetsuharu, Koyama Yoshisada, Kolev Dimitar, Munemasa Yasushi, Toyoshima Morio
Opt Express. 2016 May 30;24(11):12254-66. doi: 10.1364/OE.24.012254.
Quantum communication, and more specifically Quantum Key Distribution (QKD), enables the transmission of information in a theoretically secure way, guaranteed by the laws of quantum physics. Although fiber-based QKD has been readily available since several years ago, a global quantum communication network will require the development of space links, which remains to be demonstrated. NICT launched a LEO satellite in 2014 carrying a lasercom terminal (SOTA), designed for in-orbit technological demonstrations. In this paper, we present the results of the campaign to measure the polarization characteristics of the SOTA laser sources after propagating from LEO to ground. The most-widely used property for encoding information in free-space QKD is the polarization, and especially the linear polarization. Therefore, studying its behavior in a realistic link is a fundamental step for proving the feasibility of space quantum communications. The results of the polarization preservation of two highly-polarized lasers are presented here, including the first-time measurement of a linearly-polarized source at λ = 976 nm and a circularly-polarized source at λ = 1549 nm from space using a realistic QKD-like receiver, installed in the Optical Ground Station at the NICT Headquarters, in Tokyo, Japan.
量子通信，更具体地说是量子密钥分发（QKD），能够以理论上安全的方式传输信息，这由量子物理定律所保证。尽管基于光纤的QKD自几年前就已普遍可用，但全球量子通信网络将需要发展空间链路，而这仍有待证明。日本信息通信技术研究所（NICT）于2014年发射了一颗低地球轨道（LEO）卫星，其上搭载了一个用于在轨技术演示的激光通信终端（SOTA）。在本文中，我们展示了从LEO传播到地面后测量SOTA激光源偏振特性的活动结果。在自由空间QKD中用于编码信息的最广泛使用的特性是偏振，尤其是线偏振。因此，研究其在实际链路中的行为是证明空间量子通信可行性的基本步骤。本文展示了两个高偏振激光器的偏振保持结果，包括在日本东京NICT总部的光学地面站使用类似实际QKD的接收器首次从太空测量λ = 976 nm的线偏振源和λ = 1549 nm的圆偏振源。
