QKDs

Quantum Key Distribution, or QKD, is a secure communication method that uses principles of quantum mechanics to generate and distribute cryptographic keys. Unlike traditional encryption, which relies on the mathematical difficulty of certain problems, QKD's security is based on the fundamental laws of physics. When a quantum state is measured, it is inherently altered. This property is exploited in QKD to detect any eavesdropping attempts.

The process typically involves a sender, Alice, and a receiver, Bob. Alice transmits individual photons, each prepared in a specific quantum state, to Bob. The states of these photons represent bits of the cryptographic key. Bob measures the incoming photons, but he doesn't know which measurement basis Alice used for each photon. After the transmission, Alice and Bob publicly compare their chosen bases. They discard any bits where their bases didn't match. The remaining bits, where their bases did match, form the raw key. Any eavesdropper, Eve, attempting to intercept the photons would have to measure them, inevitably disturbing their quantum states. This disturbance would be detectable by Alice and Bob when they compare a subset of their key bits. If the error rate exceeds a certain threshold, they know the key has been compromised and discard it.

QKD offers a theoretically unbreakable method for key distribution, immune to the advances in computational power that threaten current encryption standards. It is a crucial technology for achieving forward secrecy in the quantum computing era.