Optimal Extraction of Information from Finite Quantum Ensembles

著者: S. Massar, Sandu Popescu - Physical Review Letters 1995 被引用: 775

Given only a finite ensemble of identically prepared particles, how precisely can one determine their states? We describe optimal measurement procedures in the case of spin $1/2$ particles. Furthermore, we prove that optimal measurement procedures must necessarily view the ensemble as a single composite system rather than as the sum of its components, i.e., optimal measurements cannot be realized by separate measurements on each particle.