Kvanttiavaimesiirtojärjestelmät

Kvanttiavaimesiirtojärjestelmät, or quantum key distribution (QKD) systems, are protocols designed to securely exchange cryptographic keys between two parties using the principles of quantum mechanics. These systems leverage the unique properties of quantum bits, or qubits, which can exist in multiple states simultaneously and are inherently linked through a phenomenon known as quantum entanglement. This makes QKD inherently secure against eavesdropping, as any attempt to intercept the key would disturb the quantum state and reveal the presence of an intruder.

The most well-known QKD protocol is the BB84 protocol, developed by Charles Bennett and Gilles Brassard in 1984. In this protocol, the sender (Alice) encodes the key into qubits and sends them to the receiver (Bob). Bob then measures the qubits in a randomly chosen basis and communicates the basis choices to Alice via a classical channel. Alice then reveals the correct basis for each qubit, and they discard the measurements where the bases do not match. The remaining bits form the shared secret key.

QKD systems can be implemented using various technologies, including fiber-optic cables and free-space optics. They have been successfully demonstrated over long distances and have the potential to revolutionize secure communications. However, practical implementations face challenges such as noise, loss, and the need for quantum repeaters to extend the range of QKD systems. Ongoing research aims to address these challenges and make QKD more practical and widely deployable.