{
  "abstract": "We introduce constrained quantum imaginary time evolution (CQITE), extending quantum imaginary time evolution (QITE) to constrained-search dynamics for ground-state preparation with prescribed expectation-value constraints. A central challenge in practical QITE is constructing a compact unitary representation of the imaginary-time evolution while maintaining accuracy and controlling the approximation error. We resolve this challenge by deriving an exact characterization of the imaginary-time evolution from the Krylov space generated by repeated applications of the Hamiltonian to the initial state. This characterization induces a hierarchy of operator directions expressed through nested anti-commutators. Truncating the hierarchy produces a systematic static operator pool, with polynomial size in the system size at any fixed truncation order. The resulting construction provides a principled route to compact unitary approximations of imaginary-time dynamics. Numerical tests on spin models show close agreement with exact constrained imaginary-time evolution and small constraint deviations, while a fermionic example yields energies close to the analytic constrained-search reference.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.07800",
  "author_total": 4,
  "authors": [
    {
      "name": "Daniele Cuomo"
    },
    {
      "name": "Luis Cort Barrada"
    },
    {
      "name": "Michał Studziński"
    },
    {
      "name": "Robert van Leeuwen"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/e90zc752xz06f.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.07800",
  "fulltext_url": null,
  "id": "e90zc752xz06f",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.07800",
  "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",
      "quant-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.07800",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-05",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/e90zc752xz06f.ris",
  "sources": [
    {
      "first_seen": "2026-11-06T18:21:30Z",
      "native_id": "2611.07800",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.07800"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Constrained Quantum Imaginary Time in Krylov Space",
  "title_text": "Constrained Quantum Imaginary Time in Krylov Space",
  "type": "preprint",
  "updated_at": "2026-11-08T18:20:56Z",
  "url": "https://research.draconitic.com/paper/e90zc752xz06f",
  "venue": "arXiv",
  "versions": []
}