Three-state quantum cryptography
Simon J. D. Phoenix, Stephen Mark Barnett, Anthony Chefles · Journal of Modern Optics · 2000
We introduce a protocol for quantum key distribution using three mutually non-orthogonal states. The protocol generates key bits most efficiently for three symmetric states. The generalized measurements which minimize the error probability and maximize the mutual information for such a system are known and can be implemented optically. We analyse eavesdropping strategies based on these optimal measurements.