{
  "abstract": "Accurate excited state energies are essential for interpreting fluorescence and photochemical processes, yet variational quantum eigensolvers (VQEs) on noisy intermediate-scale quantum (NISQ) hardware have largely been confined to ground states. Subspace-search VQE (SSVQE) offers a NISQ-friendly route to excited states without ancilla-based overlap measurements, however it has lacked an experimental demonstration since it requires the coherent preparation and manipulation of multiple orthogonal basis states under a shared variational unitary. Here we realize SSVQE on a photonic platform by encoding orthogonal qudit states in the orbital angular momentum of single photons and optimizing a shared variational circuit. We estimate excited state energies for a four-dimensional $\\rm{HeH^+}$ molecule and an eight-dimensional Heisenberg chain, thereby demonstrating scalable excited state eigensolving in a high-dimensional Hilbert space. Our results establish photonic qudits as a resource-efficient pathway to excited state quantum simulation.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: npj Quantum Information (2026)",
  "arxiv": "2610.11026",
  "author_total": 6,
  "authors": [
    {
      "name": "Kang-Min Hu"
    },
    {
      "name": "Myung-Hyun Sohn"
    },
    {
      "name": "Yong-Su Kim"
    },
    {
      "name": "Kwang Jo Lee"
    },
    {
      "name": "Hyun Woo Kim"
    },
    {
      "name": "Hyang-Tag Lim"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7wb9phb2apbj3.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.11026",
  "fulltext_url": null,
  "id": "7wb9phb2apbj3",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.11026",
  "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/2610.11026",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-08",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7wb9phb2apbj3.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:54Z",
      "native_id": "2610.11026",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.11026"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Demonstration of subspace-search variational quantum eigensolver using photonic orbital angular momentum qudits",
  "title_text": "Demonstration of subspace-search variational quantum eigensolver using photonic orbital angular momentum qudits",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:54Z",
  "url": "https://research.draconitic.com/paper/7wb9phb2apbj3",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1038/s41534-026-01380-2",
      "pid": "3ws8mayzz9gck",
      "relation": "published-as",
      "title": "Demonstration of subspace-search variational quantum eigensolver using photonic orbital angular momentum qudits",
      "venue": "npj Quantum Information"
    }
  ]
}