TL;DR: QKD uses quantum mechanics to distribute encryption keys with information-theoretic security. In 2025, researchers demonstrated secure quantum communication over 254 km of existing telecom fiber using
QKD uses quantum mechanics to distribute encryption keys with information-theoretic security. In 2025, researchers demonstrated secure quantum communication over 254 km of existing telecom fiber using a coherence-based protocol. China has deployed the world's largest QKD network (Beijing-Shanghai backbone, 2,000+ km). QKD is the most mature quantum networking technology, though debate continues about its practical advantages over post-quantum cryptography.
Protocol
BB84, E91, continuous-variable QKD
Range
Up to 254 km in existing telecom fiber (2025 demonstration)
Status
Commercially available (ID Quantique, Toshiba); national QKD networks in China