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Unitary Evolution Between Pure and Mixed States

B. Reznik
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Abstract

We propose an extended quantum mechanical formalism that is based on a wave operator $\vr$, which is related to the ordinary density matrix via $ρ=\vr\vr^\dagger$. This formalism allows a (generalized) unitary evolution between pure and mixed states. It also preserves much of the connection between symmetries and conservation laws. The new formalism is illustrated for the case of a two level system.

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B. Reznik. 1995-12-19. Unitary Evolution Between Pure and Mixed States. https://doi.org/10.1103/physrevlett.76.1192

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