标题： 卫星有望实现全球规模的量子网络 显示英文标题

标题： Satellites promise global-scale quantum networks

摘要： academia、政府和世界各地的工业界都在努力构建远距离量子通信网络，以实现未来的量子互联网。使用空气和光纤信道，量子通信很快面临了随着距离增加而呈指数增长的光子损失这一艰巨挑战。为了克服这一问题，量子中继器被发明出来，通过在短距离内概率性地建立纠缠态，并利用量子存储器来同步这种纠缠态的远距离传输。然而，由于量子存储器的不完善性和复杂性，基于地面的概念验证中继演示仅限于城市规模的距离。相比之下，从卫星通过外太空直接传输光子几乎不会遇到指数吸收损失，只会遭遇二次方的光束发散损失。一颗卫星成功地在超过1200公里的距离上分发了纠缠态。很明显，跨越大洲际距离（例如4000-20000公里）的量子通信很可能采用基于卫星的架构。这可能涉及卫星中的量子存储器和中继协议，或者不需要量子存储器的无记忆卫星链，光子可以通过这些卫星链简单反射，或者两者的一些组合。太空发射和经典卫星通信行业的快速发展为卫星量子通信提供了有力的支持，有望使量子通信卫星的经济部署和更容易实施成为可能。 显示英文摘要

摘要： Academia, governments, and industry around the world are on a quest to build long-distance quantum communication networks for a future quantum internet. Using air and fiber channels, quantum communication quickly faced the daunting challenge of exponential photon loss with distance. Quantum repeaters were invented to solve the loss problem by probabilistically establishing entanglement over short distances and using quantum memories to synchronize the teleportation of such entanglement to long distances. However, due to imperfections and complexities of quantum memories, ground-based proof-of-concept repeater demonstrations have been restricted to metropolitan-scale distances. In contrast, direct photon transmission from satellites through empty space faces almost no exponential absorption loss and only quadratic beam divergence loss. A single satellite successfully distributed entanglement over more than 1,200 km. It is becoming increasingly clear that quantum communication over large intercontinental distances (e.g. 4,000-20,000 km) will likely employ a satellite-based architecture. This could involve quantum memories and repeater protocols in satellites, or memory-less satellite-chains through which photons are simply reflected, or some combination thereof. Rapid advancements in the space launch and classical satellite communications industry provide a strong tailwind for satellite quantum communication, promising economical and easier deployment of quantum communication satellites.