{
  "abstract": "Deploying quantum networks over existing network infrastructures requires the same engineering foundations that underpin classical communications: quantitative models of the channel's noise and of the impairments it imposes on the transmitted information. In this work, we build such a foundation on experimental measurements, grounding the quantum-network counterparts of the two cornerstone metrics of classical link characterization - namely, the SINR and the BER - on a 7.3 km deployed metropolitan-scale fiber-loop interconnecting two campuses of the University of Naples Federico II within the national QuantumInternet.it testbed. On the noise side, we adopt a photon-counting quantum analog of the SINR - in which dark counts constitute the intrinsic noise and the photons generated by classical traffic (through either spontaneous Raman scattering or inter-fiber crosstalk) constitute the interference - and we quantify each contribution directly on the deployed loop. On the bit-error side, we consider the main degrees-of-freedom available to encode a quantum state within an optical photon - namely, polarization, time, and frequency - and we quantify for each degree the channel-induced degradation and its drift over time. These results show that a quantum fiber link, like its classical counterpart, can be captured by a small set of measurable parameters, turning quantum networking over deployed fiber from a physics demonstration into an engineering design problem. Together, they provide the key ingredients of a quantum link budget for the Quantum Internet.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.11359",
  "author_total": 3,
  "authors": [
    {
      "name": "Marcello Caleffi"
    },
    {
      "name": "Laura d'Avossa"
    },
    {
      "name": "Angela Sara Cacciapuoti"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8pcbsq858bsfp.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.11359",
  "fulltext_url": null,
  "id": "8pcbsq858bsfp",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.11359",
  "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": null,
  "pdf_url": "https://arxiv.org/pdf/2609.11359",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-10",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8pcbsq858bsfp.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:26Z",
      "native_id": "2609.11359",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.11359"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Engineering Quantum Links: Noise and Quantum-State-Degradation Metrics over Metropolitan Fiber Network",
  "title_text": "Engineering Quantum Links: Noise and Quantum-State-Degradation Metrics over Metropolitan Fiber Network",
  "type": "preprint",
  "updated_at": "2026-10-30T12:20:26Z",
  "url": "https://research.draconitic.com/paper/8pcbsq858bsfp",
  "venue": "arXiv",
  "versions": []
}