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Classical interventions in quantum systems. I. The measuring process

Asher Peres
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Abstract

The measuring process is an external intervention in the dynamics of a quantum system. It involves a unitary interaction of that system with a measuring apparatus, a further interaction of both with an unknown environment causing decoherence, and then the deletion of a subsystem. This description of the measuring process is a substantial generalization of current models in quantum measurement theory. In particular, no ancilla is needed. The final result is represented by a completely positive map of the quantum state $ρ$ (possibly with a change of the dimensions of $ρ$). A continuous limit of the above process leads to Lindblad's equation for the quantum dynamical semigroup.

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Asher Peres. 2000-02-07. Classical interventions in quantum systems. I. The measuring process. https://doi.org/10.1103/physreva.61.022116

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