Phys.org: Long-distance and secure quantum key distribution (QKD) over a free-sp
ace channel.
[1]https://phys.org/news/2021-01-long-distance-quantum-key-qkd-free-space.html

References

   1. https://phys.org/news/2021-01-long-distance-quantum-key-qkd-free-space.html