# Quantum states and generalized observables: a simple proof of Gleason's theorem.

@article{Busch2003QuantumSA, title={Quantum states and generalized observables: a simple proof of Gleason's theorem.}, author={P. Busch}, journal={Physical review letters}, year={2003}, volume={91 12}, pages={ 120403 } }

A quantum state can be understood in a loose sense as a map that assigns a value to every observable. Formalizing this characterization of states in terms of generalized probability distributions on the set of effects, we obtain a simple proof of the result, analogous to Gleason's theorem, that any quantum state is given by a density operator. As a corollary we obtain a von Neumann-type argument against noncontextual hidden variables. It follows that on an individual interpretation of quantum… Expand

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