Optimal generalized quantum measurements for arbitrary spin systems - art.no. 022113

Positive-operator-valued measurements on a finite number of N identically p repared systems of arbitrary spin J are discussed. Pure states are characte rized in terms of Bloch-like vectors restricted by a SU(2J+1) covariant con straint. This representation allows for a simple description of the equatio ns to be fulfilled by optimal measurements. We explicitly find the minimal positive-operator-valued measurement for the N=2 case, a rigorous bound for N=3, and set up the analysis for arbitrary N.