Any of various techniques that exploit quantum-mechanical phenomena, such as superposition or quantum entanglement, to generate and share between two parties a private key that can be used to encrypt and decrypt data. Current techniques also reveal any attempt to intercept the private key during its creation.
An encryption method that can detect eavesdropping. Using optical transmission to send a secret key to the other side, quantum cryptography draws on the inherent properties of photons, which become slightly altered if they are observed by an intruder. When an alteration is detected, the receiver knows the sender's key has been compromised. See cryptography and quantum computing.Polarized and Entangled PhotonsOne method relies on the polarization of the photons, which will be altered if observed (see QKD). Another method uses photon pairs that exhibit a correlation between them. Any observation along the way weakens the correlation, which can be detected.