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Bistochastic operators and quantum random variables. (English) Zbl 1495.46029

Summary: Given a positive operator-valued measure \(\nu\) acting on the Borel sets of a locally compact Hausdorff space \(X\), with outcomes in the algebra \(\mathcal{B(H)}\) of all bounded operators on a (possibly infinite-dimensional) Hilbert space \(\mathcal{H}\), one can consider \(\nu\)-integrable functions \(X \rightarrow \mathcal{B(H)}\) that are positive quantum random variables. We define a seminorm on the span of such functions which in the quotient leads to a Banach space. We consider bistochastic operators acting on this space and majorization of quantum random variables is then defined with respect to these operators. As in classical majorization theory, we relate majorization in this context to an inequality involving all possible convex functions of a certain type. Unlike the classical setting, continuity and convergence issues arise throughout the work.

MSC:

46G10 Vector-valued measures and integration
46C50 Generalizations of inner products (semi-inner products, partial inner products, etc.)
47G10 Integral operators
81P15 Quantum measurement theory, state operations, state preparations
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