{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"5b989bb4028d5704a6fe5289ddad661838ab1d8843c930988dcfd5be220ea612","created":"2026-10-03T07:18:09Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"4c733753d951db7bf9bb970b539ab0a6dde4d62183d57ad2788e28ed497ff8dd","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"qi.decoherence-classicality.darwinism-redundancy-generic","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Quantum Darwinism is the proposal that observers agree on classical facts because the environment holds many independent copies of the same information about an object, so many observers can read it without disturbing it. Whether ordinary physical interactions produce such copies, or only specially designed ones, is open.","posed_since":"","precise":"For a system $S$ coupled to an environment of $N$ fragments by a Hamiltonian $H$, quantum Darwinism requires the mutual information $I(S:F)$ to reach the plateau $H(S)$ (entropy of the pointer observable) for fragments $F$ holding a fraction $f \\ll 1$ of the environment, so that the redundancy $R = 1/f$ grows with $N$; the stricter form is a spectrum broadcast structure (fragments hold perfectly distinguishable records correlated with the same outcome). Brandao, Piani and Horodecki (Nature Communications 2015) proved that for any dynamics most fragments can access only one fixed observable of $S$, which does not by itself imply agreement on outcomes. Classify the Hamiltonians (local, with interacting environment fragments, chaotic, at finite temperature $T$) for which $R$ grows linearly with $N$ at late times.","problem_ref":null,"references":"","settled_by":"Theorems giving necessary and sufficient conditions on H for redundancy growing with N, checked on exactly solvable spin-bath and photon-scattering models.","status_note":"Redundancy plateaus were observed in engineered superconducting-qubit settings in 2025 (Zhu et al., Science Advances 11, doi:10.1126/sciadv.adx6857); genericity for natural Hamiltonians is unproved.","title":"Do generic interactions copy a system's state redundantly into its 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