{
  "id": "oai:papers.qnfo.org:two-level-system-defects-as-a-random-ensemble-counting-and-dephasing-estimates-f",
  "slug": "two-level-system-defects-as-a-random-ensemble-counting-and-dephasing-estimates-f",
  "title": "Two-Level System Defects as a Random Ensemble: Counting and Dephasing Estimates for Superconducting Qubits",
  "authors": [
    "Rowan Brad Quni-Gudzinas"
  ],
  "abstract": "Parasitic two‑level system (TLS) defects in the amorphous tunnel barriers of superconducting qubits are a major identified source of decoherence, yet device designers lack closed‑form estimates linking defect density and junction geometry to the probability that a device is degraded and to the resulting dephasing rate. This paper models the defect population of a Josephson junction as a random ensemble—a random dynamical system in which defect positions and frequencies are random variables and the qubit is a deterministic observer—and derives two complementary closed‑form results. A Poisson counting argument gives the probability that a junction hosts a strongly coupled defect: for an assumed density of 10²4 mathrmm^-3, a barrier volume of 4×10^-23 mathrmm³, and a fractional coupling window of 2×10^-3, the mean count is λ=0.08 and the single‑junction probability is P₁=0.0769; on a 100‑junction chip the expected count is $8$ and the affected‑chip probability is $0.99966$. A dephasing calculation for off‑resonant defects gives Γ_φ=5 mathrms^-1 (T_φ=0.2 s) for a five‑defect sub‑band configuration, and T_φ=800 mus under a telegraph‑noise model for a switching defect. The results convert defect decoherence from a device‑by‑device pathology into an ensemble‑level design parameter with an explicit falsification register.",
  "abstract_markdown": "Parasitic two‑level system (TLS) defects in the amorphous tunnel barriers of superconducting qubits are a major identified source of decoherence, yet device designers lack closed‑form estimates linking defect density and junction geometry to the probability that a device is degraded and to the resulting dephasing rate. This paper models the defect population of a Josephson junction as a random ensemble—a random dynamical system in which defect positions and frequencies are random variables and the qubit is a deterministic observer—and derives two complementary closed‑form results. A Poisson counting argument gives the probability that a junction hosts a strongly coupled defect: for an assumed density of $10^{24}\\ \\mathrm{m^{-3}}$, a barrier volume of $4\\times10^{-23}\\ \\mathrm{m^{3}}$, and a fractional coupling window of $2\\times10^{-3}$, the mean count is $\\lambda=0.08$ and the single‑junction probability is $P_{1}=0.0769$; on a 100‑junction chip the expected count is $8$ and the affected‑chip probability is $0.99966$. A dephasing calculation for off‑resonant defects gives $\\Gamma_{\\varphi}=5\\ \\mathrm{s^{-1}}$ ($T_{\\varphi}=0.2\\ \\mathrm{s}$) for a five‑defect sub‑band configuration, and $T_{\\varphi}=800\\ \\mu\\mathrm{s}$ under a telegraph‑noise model for a switching defect. The results convert defect decoherence from a device‑by‑device pathology into an ensemble‑level design parameter with an explicit falsification register.",
  "date": "2026-10-12",
  "first_published": "2026-10-12",
  "last_revised": "2026-10-21T08:41:49Z",
  "modified": "2026-10-21T08:41:49Z",
  "version": "2.0.0",
  "version_count": 2,
  "language": "en",
  "keywords": [],
  "quality_tags": [
    "High-quality scholarly research",
    "open-access scholarly work",
    "versioned research publication"
  ],
  "quality_label": "High-quality scholarly research",
  "quality_basis": "QNFO publisher classification for open-access, versioned research with a public revision history and reader correction channel; this is not a claim of independent peer review.",
  "quality_evidence_url": "https://qnfo.org/about",
  "peer_review_status": "Not independently peer-reviewed",
  "resource_type": "ScholarlyArticle",
  "doi": null,
  "doi_url": null,
  "url": "https://papers.qnfo.org/papers/two-level-system-defects-as-a-random-ensemble-counting-and-dephasing-estimates-f",
  "license_url": "https://legal.qnfo.org/",
  "license_spdx": null,
  "sha256": "e5c616dbc591eb2d33079c057f8d8ccd7098dd23df9a100c41ed62841dc4ebf9",
  "version_url": "https://papers.qnfo.org/papers/two-level-system-defects-as-a-random-ensemble-counting-and-dephasing-estimates-f/v/2.0.0",
  "datacite": {
    "schemaVersion": "http://datacite.org/schema/kernel-4",
    "identifiers": [
      {
        "identifier": "https://papers.qnfo.org/papers/two-level-system-defects-as-a-random-ensemble-counting-and-dephasing-estimates-f",
        "identifierType": "URL"
      }
    ],
    "creators": [
      {
        "name": "Rowan Brad Quni-Gudzinas",
        "nameType": "Personal",
        "nameIdentifiers": [
          {
            "nameIdentifier": "https://orcid.org/0009-0002-4317-5604",
            "nameIdentifierScheme": "ORCID",
            "schemeUri": "https://orcid.org"
          }
        ]
      }
    ],
    "titles": [
      {
        "title": "Two-Level System Defects as a Random Ensemble: Counting and Dephasing Estimates for Superconducting Qubits"
      }
    ],
    "publisher": "QNFO",
    "publicationYear": "2026",
    "resourceType": {
      "resourceTypeGeneral": "Text",
      "resourceType": "ScholarlyArticle"
    },
    "subjects": [
      {
        "subject": "High-quality scholarly research",
        "subjectScheme": "QNFO publisher classification",
        "schemeUri": "https://qnfo.org/about"
      },
      {
        "subject": "open-access scholarly work",
        "subjectScheme": "QNFO publisher classification",
        "schemeUri": "https://qnfo.org/about"
      },
      {
        "subject": "versioned research publication",
        "subjectScheme": "QNFO publisher classification",
        "schemeUri": "https://qnfo.org/about"
      }
    ],
    "dates": [
      {
        "date": "2026-10-12",
        "dateType": "Issued"
      },
      {
        "date": "2026-10-21",
        "dateType": "Updated"
      }
    ],
    "language": "en",
    "version": "2.0.0",
    "rightsList": [
      {
        "rightsUri": "https://legal.qnfo.org/"
      }
    ],
    "descriptions": [
      {
        "description": "Parasitic two‑level system (TLS) defects in the amorphous tunnel barriers of superconducting qubits are a major identified source of decoherence, yet device designers lack closed‑form estimates linking defect density and junction geometry to the probability that a device is degraded and to the resulting dephasing rate. This paper models the defect population of a Josephson junction as a random ensemble—a random dynamical system in which defect positions and frequencies are random variables and the qubit is a deterministic observer—and derives two complementary closed‑form results. A Poisson counting argument gives the probability that a junction hosts a strongly coupled defect: for an assumed density of 10²4 mathrmm^-3, a barrier volume of 4×10^-23 mathrmm³, and a fractional coupling window of 2×10^-3, the mean count is λ=0.08 and the single‑junction probability is P₁=0.0769; on a 100‑junction chip the expected count is $8$ and the affected‑chip probability is $0.99966$. A dephasing calculation for off‑resonant defects gives Γ_φ=5 mathrms^-1 (T_φ=0.2 s) for a five‑defect sub‑band configuration, and T_φ=800 mus under a telegraph‑noise model for a switching defect. The results convert defect decoherence from a device‑by‑device pathology into an ensemble‑level design parameter with an explicit falsification register.",
        "descriptionType": "Abstract"
      },
      {
        "description": "Publisher quality classification: High-quality scholarly research. QNFO publisher classification for open-access, versioned research with a public revision history and reader correction channel; this is not a claim of independent peer review.",
        "descriptionType": "Other"
      },
      {
        "description": "Peer review status: Not independently peer-reviewed",
        "descriptionType": "Other"
      }
    ],
    "formats": [
      "text/html"
    ]
  }
}