What is quantum cryptography and how does the photonic “key” work ?
Quantum cryptography uses quantum mechanics for secure communications. Unlike traditional cryptography, which depends on the computational complexity of mathematical techniques to restrict the possibility that eavesdroppers might learn the contents of encrypted messages, quantum cryptography depends on the fact that naive attempts to read quantum information will destroy the information (ie. there is no way to copy unknown quantum states). For the message participants, a combination of quantum and classical techniques is used to produce a key which can be proven to be secure —that is, a produced hidden key cannot have been read by any other than the intended participants. In quantum information, eavesdropping can be viewed as measurements on a physical object — in this case the carrier of the information. Using quantum phenomena such as quantum superpositions or quantum entanglement one can design and implement a communication system which can always detect eavesdropping. This is becau
