{
  "abstract": "We compute the evanescent-wave Johnson noise (EWJN) in the vacuum half-space above a superconductor, and the resulting relaxation time ($T_1$) of spin and charge qubits placed at nanometer distances from the surface. The electromagnetic response is described by a single microscopic transverse current-response kernel $Q(q, ω)$ for a BCS superconductor. This is computed for varying densities of both non-magnetic impurities and magnetic impurities, for arbitrary frequency and temperature and for wave vectors $q \\ll k_F$ (the Fermi wavevector). When combined with the fluctuation-dissipation theorem and the nonlocal surface impedances of the half-space, this yields the magnetic and electric field noise at any distance $z \\gg k_F^{-1}$ from the surface, from which we obtain $T_1$. Just below $T_c$ the magnetic noise is enhanced relative to the normal state by the coherence (Hebel-Slichter-type) peak of the dissipative conductivity and drops exponentially at lower temperatures; the electric noise shows no coherence peak. The theory predicts that there is a zero-temperature noise floor induced by magnetic impurities. In the gapless regime produced by pair breaking, the finite subgap density of states $ν(0)$ yields a temperature-independent noise spectral density and a relaxation rate bounded by $T_1^{-1}(T)\\le[ν(0)/ν_F]^{2}\\,T_{1,N}^{-1}(T)$ for $T\\ll T_c$, with equality in the extreme nonlocal regime. Here $ν(0)$ and $ν_F$ are the superconducting and normal-state densities of states at the Fermi energy, and $T_{1,N}(T)$ is the relaxation time the same electrode would produce in its normal state at the same temperature.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.36497",
  "author_total": 6,
  "authors": [
    {
      "name": "Hruday Mallubhotla"
    },
    {
      "name": "Gustav Romare"
    },
    {
      "name": "Ilya Esterlis"
    },
    {
      "name": "Maxim Vavilov"
    },
    {
      "name": "Robert Joynt"
    },
    {
      "name": "Alex Levchenko"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6f1ea07z1gdm0.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.36497",
  "fulltext_url": null,
  "id": "6f1ea07z1gdm0",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.36497",
  "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.supr-con"
    ],
    [
      "arxiv",
      "quant-ph"
    ],
    [
      "openalex",
      "3104|Physics of Superconductivity and Magnetism"
    ]
  ],
  "openalex": "W7214925086",
  "pdf_url": "https://arxiv.org/pdf/2609.36497",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6f1ea07z1gdm0.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:31Z",
      "native_id": "2609.36497",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.36497"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.supr-con",
      "subfield": "condensed-matter"
    },
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Evanescent-wave Johnson Noise from Superconductors",
  "title_text": "Evanescent-wave Johnson Noise from Superconductors",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:31Z",
  "url": "https://research.draconitic.com/paper/6f1ea07z1gdm0",
  "venue": "arXiv",
  "versions": []
}