Quantum key distribution

Quantum key distribution (QKD) is a secure communication method that uses quantum mechanics to enable two parties to generate a shared random secret key. Its security rests on the No-Cloning Theorem: any eavesdropper measuring the quantum states disturbs them and reveals their presence. The foundational protocol is the BB84 Protocol, though variants such as Decoy State QKD address practical weaknesses. QKD requires a dedicated Quantum channel and cannot use classical amplifiers, making quantum repeaters essential for long-distance networks.

QKD relocates trust from computational hardness to physical law. Whether that is a genuine advance or a change of costume remains debated.