QKDProtokolle

QKD Protokolle, or Quantum Key Distribution protocols, are methods for establishing a shared secret key between two parties, traditionally named Alice and Bob, using principles of quantum mechanics. The fundamental advantage of QKD is its inherent security, which is guaranteed by the laws of physics, rather than the computational difficulty of breaking cryptographic algorithms. Any attempt by an eavesdropper, Eve, to intercept or measure the quantum signals carrying the key information will inevitably disturb the quantum state, thus alerting Alice and Bob to the presence of an eavesdropper.

Several QKD protocols exist, each with its unique approach to encoding information onto quantum states and detecting eavesdropping. The BB84 protocol, developed by Charles Bennett and Gilles Brassard in 1984, is one of the earliest and most well-known. It utilizes photons polarized in one of four states, corresponding to two different bases. Alice randomly chooses a basis for each photon she sends, and Bob randomly chooses a basis to measure each arriving photon. They then publicly communicate which bases they used, discarding measurements where their bases did not match. The remaining measurements, if performed correctly, will result in identical sequences for Alice and Bob, forming the shared secret key.

Other notable QKD protocols include the E91 protocol, which leverages entanglement, and the B92 protocol, a simplified version of BB84. Continuous-variable QKD protocols, which use the continuous properties of quantum states like amplitude and phase, offer alternative approaches. The practical implementation of QKD involves sophisticated hardware, including single-photon sources, detectors, and quantum channels, often optical fibers or free-space links. Despite ongoing research and development, QKD technology is moving towards practical deployment for securing sensitive communications.