Unambiguous Measurements Based Quantum Cryptography

A new quantum cryptography (quantum key distribution) scheme based on unambiguous measurements is presented, which is secure against any individual attack allowed by quantum physics. By carefully constructing the unambiguous measurements elements a higher efficiency than previous protocols is achieved. Furthermore, an equality for the probability of the participant's reliable measurement outcome and the polarization angle that he chooses when distinguishing between two non-orthogonal states is also derived in this paper.