Localizing Eavesdroppers Inside a Quantum Channel Using Stimulated Brillouin Scattering

TL;DR: QKD secret key sharing is secure against eavesdropping due to the quantum nature of the shared states, which manifests in detectable changes upon interception.

Abstract: While modern communication systems pose a high standard of security using state-of-the-art encryption techniques based on computational hardness problems, quantum key distribution (QKD) offers a unique advantage using the laws of quantum mechanics. A secret key is shared between two parties, using quantum states of light over a quantum channel. Due to the quantum nature of the states, any interception or other way of eavesdropping will manifest in the distortion of the quantum state resulting in a change of accessible parameters. Whenever such a change of parameters is noticed, the shared key is marked unsecure and hashed down largely or, in the worst case, discarded.