{
  "abstract": "Understanding the qubit environment is central to fault-tolerant superconducting quantum computation. Characterization typically relies on relaxation, leaving excitation largely underexplored. Here, we access this information with time-resolved broadband excitation spectroscopy. The resulting qubit excitation spectrum reveals a highly structured landscape, interspersed with cold regions. Combined with postselection, this technique enables full reconstruction of the noise power spectral density (PSD) and separates quantum from classical noise. With feed-forward, it exposes long-lived two-level-systems (TLSs), whose relaxation times span tens of microseconds to milliseconds - uncovering an intrinsic link between the qubit-TLS coupling and TLS relaxation. The data suggest that the long-lived TLSs are intrinsic to the qubit environment, and can cause excitation that lasts for many qubit operation cycles. Consequently, the environment retains a memory of prior dynamics, and properties like gate fidelity become non-Markovian and protocol-dependent. The presented approach enables identifying and bypassing the hidden roadblocks formed by long-lived TLSs in fault-tolerant quantum computation.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.31280",
  "author_total": 13,
  "authors": [
    {
      "name": "J. R. Guimarães"
    },
    {
      "name": "Y. Liu"
    },
    {
      "name": "Y. Gao"
    },
    {
      "name": "Y. Haddad"
    },
    {
      "name": "A. Galicia"
    },
    {
      "name": "D. A. Volkov"
    },
    {
      "name": "J. T. Schmieder"
    },
    {
      "name": "H. Bhardwaj"
    },
    {
      "name": "M. Neis"
    },
    {
      "name": "J. Cereijo"
    },
    {
      "name": "M. Jerger"
    },
    {
      "name": "P. A. Bushev"
    },
    {
      "name": "R. Barends"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bgncehcn89gmz.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.31280",
  "fulltext_url": null,
  "id": "bgncehcn89gmz",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.31280",
  "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.mes-hall"
    ],
    [
      "arxiv",
      "quant-ph"
    ],
    [
      "openalex",
      "1702|Quantum Information and Cryptography"
    ]
  ],
  "openalex": "W7214583710",
  "pdf_url": "https://arxiv.org/pdf/2609.31280",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-25",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/bgncehcn89gmz.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:24:52Z",
      "native_id": "2609.31280",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.31280"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mes-hall",
      "subfield": "condensed-matter"
    },
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Quantum environment afterglow from broadband excitation spectroscopy in superconducting qubits",
  "title_text": "Quantum environment afterglow from broadband excitation spectroscopy in superconducting qubits",
  "type": "preprint",
  "updated_at": "2026-10-30T12:24:52Z",
  "url": "https://research.draconitic.com/paper/bgncehcn89gmz",
  "venue": "arXiv",
  "versions": []
}