{
  "abstract": "We determine the exact entanglement structure of the conditional state obtained by measuring $m$ corresponding rungs ($m\\leq N/2$) in two identical copies of an arbitrary half-filled free fermion Gaussian state and post-selecting the same normalized single-fermion state ($|ψ\\rangle = u|10\\rangle+v|01\\rangle$, where 0 and 1 denote the fermion occupancy on each sites) on each rung. For $m<N/2$, the conditional wavefunction generally depends on the initial state. Nevertheless, whenever the selected outcome has nonzero probability, the state on the unmeasured sites remains Gaussian and factorizes exactly into $N-m$ different orthogonal modes including $m$ inter-copy entangling modes and $N-2m$ spectator modes localized in one copy. Consequently, the entanglement entropy between the unmeasured parts of the two copies is $S=m h_2(|v|^2)$, independent of the initial state, where $h_2(x)=-x\\ln x-(1-x)\\ln(1-x)$. The success probability is given by $P_m=\\det C_L\\det(I_m-C_L)=\\det(C_{LR}C_{RL})$, determined solely by the initial correlations and independent of ($u$,$v$). Equal-weight Bell post-selection serves as a special case that achieves the maximal entanglement swapping.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2608.29933",
  "author_total": 1,
  "authors": [
    {
      "name": "Jiyuan Fang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7ey2fd42w5f57.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.29933",
  "fulltext_url": null,
  "id": "7ey2fd42w5f57",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.29933",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.stat-mech"
    ],
    [
      "arxiv",
      "math-ph"
    ],
    [
      "arxiv",
      "math.MP"
    ],
    [
      "arxiv",
      "quant-ph"
    ],
    [
      "openalex",
      "1702|Quantum Information and Cryptography"
    ]
  ],
  "openalex": "W7204964282",
  "pdf_url": "https://arxiv.org/pdf/2608.29933",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-30",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7ey2fd42w5f57.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:41Z",
      "native_id": "2608.29933",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.29933"
    }
  ],
  "subjects": [
    {
      "field": "mathematics",
      "origin": "arxiv:math-ph",
      "subfield": "mathematical-physics"
    },
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    },
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.stat-mech",
      "subfield": "statistical-nonlinear"
    }
  ],
  "title": "Exact Entanglement Swapping through Single-Occupancy Measurements in Gaussian Fermion States",
  "title_text": "Exact Entanglement Swapping through Single-Occupancy Measurements in Gaussian Fermion States",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:48Z",
  "url": "https://research.draconitic.com/paper/7ey2fd42w5f57",
  "venue": "arXiv",
  "versions": []
}