{
  "abstract": "Calibrating a quantum processor means estimating gate-error parameters from data, and a hard-to-estimate parameter is usually assumed to leave a weak signature more repetitions will resolve. Coherent over-rotations break that premise. For commuting single- and two-qubit transverse over-rotations with known support on a computational-basis input, the passive histogram is exactly invariant under a sign group acting on the coherent angles, of order $2^{n+1}$ for the complete family with $n\\ge2$, so no estimator resolves the signs uniformly at any sample size. A calibration correction applied with the wrong sign doubles the rotation error it should remove. At zero angle the obstruction turns continuous, with a Fisher information singular along every coherent direction and an infinite Cramér-Rao bound. At generic angles the continuous defect clears for $5\\le n\\le8$, the range we compute, while the sign degeneracy persists. Covering the support removes both, and a design resolves the signed angles uniformly exactly when it covers. On $|η_R|<π/2$, $0\\le p_R<1/2$ coverage is constructive, returning each angle in closed form from a ratio of two measured expectations without knowing the rates. A twirl-free code of $\\lceil\\log_2(n+1)\\rceil$ added product-Pauli settings covers, and for the complete family none uses fewer. Conditioning then sets the Cramér-Rao cost, and we give its floor explicitly. Exact computation matches the theory, the passive fit stays at chance on the signs at every budget while the closed-form inverse recovers them, and angle magnitudes on two IBM Heron processors follow the conditioning ordering.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2607.21663",
  "author_total": 9,
  "authors": [
    {
      "name": "Yi Pan"
    },
    {
      "name": "Meng Hsiu Tsai"
    },
    {
      "name": "Weihang You"
    },
    {
      "name": "Hanqi Jiang"
    },
    {
      "name": "Junhao Chen"
    },
    {
      "name": "Wei Zhang"
    },
    {
      "name": "Isaac Lyngaas"
    },
    {
      "name": "Yingfeng Wang"
    },
    {
      "name": "Tianming Liu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/cg0a7sb08erg5.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.21663",
  "fulltext_url": null,
  "id": "cg0a7sb08erg5",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.21663",
  "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",
      "1702|Quantum Computing Algorithms and Architecture"
    ]
  ],
  "openalex": "W7171407934",
  "pdf_url": "https://arxiv.org/pdf/2607.21663",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-24",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/cg0a7sb08erg5.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:24:52Z",
      "native_id": "2607.21663",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.21663"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Identifying the Sign of Coherent Over-Rotations with Logarithmically Many Pauli Settings",
  "title_text": "Identifying the Sign of Coherent Over-Rotations with Logarithmically Many Pauli Settings",
  "type": "preprint",
  "updated_at": "2026-10-30T12:24:52Z",
  "url": "https://research.draconitic.com/paper/cg0a7sb08erg5",
  "venue": "arXiv",
  "versions": []
}