Discrimination of quantum observables using limited resources
Mário Ziman, Teiko Heinosaari · Physical Review A · 2008
We address the problem of unambiguous discrimination and identification among quantum observables. We set a general framework and investigate in detail the case of qubit observables. In particular, we show that perfect discrimination with two shots is possible only for sharp qubit observables (e.g., Stern-Gerlach apparatuses) associated with mutually orthogonal directions. We also show that for sharp qubit observables associated to nonorthogonal directions unambiguous discrimination with an inconclusive result is always possible.