Physics
Quantum Key Distribution over Terrestrial Free-Space Optical Links
Quick fact
Quantum keys sent over free-space links use individual photons, and any eavesdropping attempt disturbs their quantum state, immediately alerting the sender and receiver.
Why this is interesting
You've probably sent encrypted messages over the internet, but what if the cables were replaced by open air? Quantum key distribution over free-space optical links can send unbreakable encryption keys through the sky—but how does it survive rain, fog, and even the Earth's curvature?