{
  "abstract": "Occupation-Space Variational Quantum Optimization (OS-VQO) is introduced as a new framework for quantum electronic structure calculations in which the quantum variational object is an occupation state rather than a many-electron wavefunction. Consequently, the quantum processor operates directly on the occupation numbers, the fundamental variational variables of Natural Orbital Functional Theory (NOFT). The framework is realized through a logarithmically scaling qudit encoding of electron-pair occupation spaces and a hierarchical variational circuit that spans the complete physically admissible occupation manifold while enforcing all N-representability constraints by construction. Noiseless quantum simulations and raw executions on IBM Quantum processors for hydrogen systems up to H216 demonstrate excellent agreement without error mitigation or post-processing, constituting, to the best of our knowledge, the largest raw quantum hardware demonstration reported for a strongly correlated electronic structure calculation. These results demonstrate that quantum variational optimization need not rely on many-electron wavefunctions, opening a new direction for quantum electronic structure calculations based on functional theories.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "name": "Edison X. Salazar"
    },
    {
      "name": "Mario Piris",
      "orcid": "0000-0003-0222-2953"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8dsa079vnxnw4.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15008226/v1",
  "fulltext_url": null,
  "id": "8dsa079vnxnw4",
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  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008226/v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1702|Quantum Computing Algorithms and Architecture"
    ]
  ],
  "openalex": "W7207663531",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-02",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/8dsa079vnxnw4.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:17Z",
      "native_id": "10.26434/chemrxiv.15008226",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008226/v1"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "source:chemrxiv",
      "subfield": "general"
    }
  ],
  "title": "Occupation-Space Variational Quantum Optimization",
  "title_text": "Occupation-Space Variational Quantum Optimization",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:17Z",
  "url": "https://research.draconitic.com/paper/8dsa079vnxnw4",
  "venue": "ChemRxiv",
  "versions": []
}