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Quantum Darwinism: Entanglement, branches, and the emergent classicality of redundantly stored quantum information

Robin Blume-Kohout·W. H. Zurek
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Abstract

We lay a comprehensive foundation for the study of redundant information storage in decoherence processes. Redundancy has been proposed as a prerequisite for objectivity, the defining property of classical objects. We consider two ensembles of states for a model universe consisting of one system and many environments: the first consisting of arbitrary states, and the second consisting of ``singly-branching'' states consistent with a simple decoherence model. Typical states from the random ensemble do not store information about the system redundantly, but information stored in branching states has a redundancy proportional to the environment's size. We compute the specific redundancy for a wide range of model universes, and fit the results to a simple first-principles theory. Our results show that the presence of redundancy divides information about the system into three parts: classical (redundant); purely quantum; and the borderline, undifferentiated or ``nonredundant,'' information.

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Robin Blume-Kohout, W. H. Zurek. 2005-10-13. Quantum Darwinism: Entanglement, branches, and the emergent classicality of redundantly stored quantum information. https://doi.org/10.1103/physreva.73.062310

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