Quantum key distribution (QKD) is a technique that enables secure communications between devices using a cryptographic protocol that is partly based on quantum mechanics. This communication method ultimately allows two parties to encrypt and decrypt messages they send to each other using a unique key that is unknown to other parties.
![](https://scx1.b-cdn.net/csz/news/tmb/2021/longdistance.jpg)
Source:
https://phys.org/news/2021-01-long-distance-quantum-key-qkd-free-space.html