{
  "abstract": "We introduce a distinct route for extending classical atomistic spin dynamics into the quantum regime for arbitrary spin $s$, based on a variational product-state \\textit{ansatz} that includes both pure and mixed local states. By construction, intersite entanglement -- expected to remain negligible even on very short time scales in many real materials -- is excluded, while local quantum effects are retained through the nonclassical structure of $s\\geq 1$ density operators. Nonlinear dynamics arise from both the mean-field interdependence of the local states and the state-dependent dissipative terms. The framework recovers classical spin dynamics for $s=\\frac{1}{2}$ while allowing genuinely quantum local dynamics for higher spins. It clarifies the variational and geometric origin of the inequivalence between quantum Landau-Lifshitz and Landau-Lifshitz-Gilbert dynamics, provides a criterion for their equivalence under a common time rescaling, establishes connections with the classical theory through two qualitatively distinct limits ($s\\to\\infty$ and a large number of quantum spins $N$), and allows realistic $\\mathcal{O}(N)$ simulations of quantum spin dynamics in materials.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.05521",
  "author_total": 2,
  "authors": [
    {
      "name": "Ivan P. Miranda"
    },
    {
      "name": "Erik Sjöqvist"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/4r9v045jr2gsk.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.05521",
  "fulltext_url": null,
  "id": "4r9v045jr2gsk",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.05521",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mes-hall"
    ],
    [
      "arxiv",
      "cond-mat.str-el"
    ],
    [
      "arxiv",
      "quant-ph"
    ],
    [
      "openalex",
      "3107|Quantum many-body systems"
    ]
  ],
  "openalex": "W7220671035",
  "pdf_url": "https://arxiv.org/pdf/2610.05521",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-18",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/4r9v045jr2gsk.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:30:52Z",
      "native_id": "2610.05521",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.05521"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mes-hall",
      "subfield": "condensed-matter"
    },
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Nonlinear quantum multi-spin dynamics without entanglement",
  "title_text": "Nonlinear quantum multi-spin dynamics without entanglement",
  "type": "preprint",
  "updated_at": "2026-10-30T12:33:41Z",
  "url": "https://research.draconitic.com/paper/4r9v045jr2gsk",
  "venue": "arXiv",
  "versions": []
}