Ca. Fuchs et A. Peres, QUANTUM-STATE DISTURBANCE VERSUS INFORMATION GAIN - UNCERTAINTY RELATIONS FOR QUANTUM INFORMATION, Physical review. A, 53(4), 1996, pp. 2038-2045
When an observer wants to identify a quantum state, which is known to
be one of a given set of nonorthogonal states, the act of observation
causes a disturbance to that state. We investigate the trade-off betwe
en the information gain and that disturbance. This issue has important
applications in quantum cryptography. The optimal detection method, f
or a given tolerated disturbance, is explicitly found in the case of t
wo equiprobable nonorthogonal pure states.