{"paper":{"title":"Opportunistic QKD: Exploiting Idle Capacity of Classical WDM Systems","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"Opportunistic QKD can repurpose 45-65 percent of unused spectrum in classical WDM systems by borrowing idle channels while protecting classical traffic.","cross_cats":[],"primary_cat":"quant-ph","authors_text":"Alonso Viladomat Jasso, Janis N\\\"otzel, Pere Munar Vallespir, Sumit Chaudhary","submitted_at":"2026-04-14T17:16:44Z","abstract_excerpt":"While QKD has been proven in lab environments, large-scale implementation requires integration with existing infrastructure. This paper proposes an opportunistic QKD framework that takes advantage of idle spectral capacity, that is, unused channels in classical fibers, to perform QKD while prioritizing classical traffic. To mitigate crosstalk during the co-propagation of classical and quantum signals, we require a guardband of unused channels between classical and quantum signals. We propose a stochastic traffic model, with a deterministic day-night cycle and fractional Gaussian noise. Monte-C"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"Monte-Carlo simulations of an 80-channel WDM system with our stochastic traffic model demonstrate that 45-65% of unused spectrum can be repurposed for QKD, depending on the traffic conditions.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The stochastic traffic model with deterministic day-night cycle and fractional Gaussian noise accurately represents real-world classical traffic patterns in WDM systems, enabling reliable estimation of idle capacity.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Monte-Carlo simulations show that 45-65% of unused spectrum in an 80-channel WDM system can be repurposed for QKD using a stochastic traffic model and key reservoir management with defined reliability metrics.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Opportunistic QKD can repurpose 45-65 percent of unused spectrum in classical WDM systems by borrowing idle channels while protecting classical traffic.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"90470ec9623f52b99e8cfbd552bdd5828072dbdcce07c195798ff3574d2ec15b"},"source":{"id":"2604.12982","kind":"arxiv","version":2},"verdict":{"id":"7951e0ae-e0ce-446d-a738-e46f606c2545","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-10T15:38:25.985217Z","strongest_claim":"Monte-Carlo simulations of an 80-channel WDM system with our stochastic traffic model demonstrate that 45-65% of unused spectrum can be repurposed for QKD, depending on the traffic conditions.","one_line_summary":"Monte-Carlo simulations show that 45-65% of unused spectrum in an 80-channel WDM system can be repurposed for QKD using a stochastic traffic model and key reservoir management with defined reliability metrics.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The stochastic traffic model with deterministic day-night cycle and fractional Gaussian noise accurately represents real-world classical traffic patterns in WDM systems, enabling reliable estimation of idle capacity.","pith_extraction_headline":"Opportunistic QKD can repurpose 45-65 percent of unused spectrum in classical WDM systems by borrowing idle channels while protecting classical traffic."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2604.12982/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}