The recent rapid growth of satellite-constellation programmes for remote sensing and communications, enabled by the availability of small-sized and low-cost satellites, has provided impetus for the development of high-capacity laser communication (lasercom) in space. Quantum-limited communication can enhance the performance of lasercom and is also a prerequisite for the intrinsically hack-proof secure communication known as quantum key distribution. Here, we report a quantum-limited communication experiment between a microsatellite (48 kg, 50 cm cube) in low Earth orbit and a ground station. Non-orthogonal polarization states were transmitted from the satellite at a 10 MHz repetition rate. On the ground, by post-processing the received quantum states with ∼0.146 photons per pulse, clock data recovery and polarization reference-frame synchronization were successfully achieved, even under remarkable Doppler shifts. The quantum states were discriminated by a receiver with four photon counters, with a quantum bit error rate below 5%, validating the applicability of our technology to satellite-to-ground lasercom and quantum key distribution.

中文翻译：

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使用50公斤级微卫星的卫星对地面量子限制通信

由于小型和低成本卫星的可用性，近来用于遥感和通信的卫星星座计划迅速增长，这为空间大容量激光通信（lasercom）的发展提供了动力。量子受限通信可以提高lasercom的性能，这也是称为量子密钥分发的本质上防黑客攻击的安全通信的先决条件。在这里，我们报告了低地球轨道上的微卫星（48 kg，50 cm立方体）与地面站之间的量子受限通信实验。非正交极化状态是从卫星以10 MHz的重复频率发送的。在地面上，通过对接收到的每脉冲约0.146个光子的量子态进行后处理，即使在明显的多普勒频移下，时钟数据恢复和极化参考帧同步也能成功实现。带有四个光子计数器的接收器区分了量子态，量子误码率低于5％，这验证了我们的技术在卫星对地面Lasercom和量子密钥分配中的适用性。