As it circled the Earth one night in 2017, the Chinese satellite Mozi, also called Micius, aimed a laser at a ground station in northeastern China (Fig. 1). Then, as it traveled toward Europe and into range, it directed a beam at a different receiver in Austria. These transmissions, delivered to sites 7600 km apart, were noteworthy because they marked the first time a satellite had relayed secret quantum keys for decrypting and viewing messages. With the keys, scientists in China and Austria were able to exchange and decipher encrypted images. And on 29 September 2017, the researchers used the system to set up an encrypted 75-minute video conference between members of the Chinese Academy of Sciences in Beijing and their counterparts at the Austrian Academy of Sciences in Vienna [1].
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