Quantum Key Distribution (QKD)
A method of distributing encryption keys using quantum mechanics, where any eavesdropping attempt physically disturbs the quantum states and is therefore detectable.
Quantum key distribution (QKD) is a method for securely distributing cryptographic keys using quantum mechanical properties. It exploits the principle that measuring a quantum state disturbs it: any attempt to intercept the key will leave a detectable trace.
The most common QKD protocol, BB84, uses single photons in specific quantum states to transmit key bits. Because quantum states cannot be copied (the no-cloning theorem) and measuring them disturbs them, interception is physically detectable.
QKD is often called 'information-theoretically secure' because its security comes from physics, not from computational complexity. It is not vulnerable to attacks by quantum computers in the way classical encryption algorithms are.