Quantum cryptography (QKD) provides theoretically unbreakable encryption based on quantum physics principles.

QKD (Quantum Key Distribution) uses quantum properties (no-cloning theorem, measurement disturbance) to detect eavesdropping during key exchange. If intercepted, quantum states change, alerting parties. Provides information-theoretic security, unlike computational security of RSA/ECC. Deployed in limited networks; scaling challenges remain.