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Conditional Density Matrix: Systems and Subsystems in Quantum Mechanics

V. V. Belokurov·O. A. Khrustalev·V. A. Sadovnichy·O. D. Timofeevskaya
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Abstract

A new quantum mechanical notion -- Conditional Density Matrix -- is discussed and is applied to describe some physical processes. This notion is a natural generalization of von Neumann density matrix for such processes as divisions of quantum systems into subsystems and reunifications of subsystems into new joint systems. Conditional Density Matrix assigns a quantum state to a subsystem of a composite system under condition that another part of the composite system is in some pure state.

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V. V. Belokurov, O. A. Khrustalev, V. A. Sadovnichy, O. D. Timofeevskaya. 2002-10-22. Conditional Density Matrix: Systems and Subsystems in Quantum Mechanics. https://arxiv.org/abs/quant-ph/0210149

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