Quantum key distribution
QKD
A method of exchanging keys using quantum physics, where eavesdropping disturbs the transmission detectably. QKD needs dedicated hardware and links, and is not a substitute for post-quantum cryptography — the NSA does not recommend it for national-security systems.
In practice
QKD protects a key in transit over a specific link. PQC protects data everywhere, using existing infrastructure.
Related terms
Cryptographic algorithms designed to resist attacks by both classical and quantum computers. PQC runs on ordinary hardware today — it is not quantum technology, it is classical maths chosen because no efficient quantum attack against it is known.
A correlation between quantum systems such that the state of one cannot be described independently of the other, regardless of distance. It is a resource for quantum algorithms and for quantum key distribution.