{"paper":{"title":"Entangled Telecom Photon Generation using Twisted Van der Waals Crystals","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"A 90-degree twist in NbOBr2 van der Waals crystals produces polarization-entangled telecom photons with over 95% fidelity.","cross_cats":["cond-mat.other"],"primary_cat":"physics.optics","authors_text":"Andrea Balocchi, Delphine Lagarde, Deng Hu, Di Lin, Gang Wang, Hanting Li, Konstantinos Mourzidis, Liu Yang, Nidhin Prasannan, Pierre Renucci, Vishwas Jindal, Wenchen Yang, Xavier Marie, Zhiwei Wang","submitted_at":"2026-05-14T09:02:13Z","abstract_excerpt":"Nanoscale quantum light sources are essential building blocks for integrated quantum photonic systems. Here, we report a wavelength-scale entangled-photon source based on van der Waals-engineered NbOBr$_2$, and benchmark its performance for telecom-wavelength quantum light generation. By exploiting the material's second-order nonlinearity, we generate quantum-correlated photon pairs via spontaneous parametric down-conversion. We then use a 90$^{\\circ}$ twisted stacking to induce quantum interference in photon-pair generation, yielding polarization-entangled photons. This approach enables tunab"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"We experimentally obtain entanglement fidelities exceeding 95% for Bell states, along with a high coincidence-to-accidental ratio of ∼335, and a brightness approximately one order of magnitude higher than recently reported telecom sources based on transition metal dichalcogenide (TMD) 2D materials.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The 90° twisted stacking specifically induces the quantum interference responsible for polarization entanglement, rather than arising from other material properties, alignment artifacts, or unaccounted experimental factors.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Twisted NbOBr2 van der Waals crystals generate polarization-entangled telecom photons with >95% Bell-state fidelity via SPDC, showing higher brightness than prior TMD-based sources.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"A 90-degree twist in NbOBr2 van der Waals crystals produces polarization-entangled telecom photons with over 95% fidelity.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"33606771eeffa2c059248fe379920f89cd6545e10b3e8a4207eb0dca9b9d5f5d"},"source":{"id":"2605.14592","kind":"arxiv","version":1},"verdict":{"id":"282cd860-2fe8-4006-aa93-00a5085e0489","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-15T01:20:53.521910Z","strongest_claim":"We experimentally obtain entanglement fidelities exceeding 95% for Bell states, along with a high coincidence-to-accidental ratio of ∼335, and a brightness approximately one order of magnitude higher than recently reported telecom sources based on transition metal dichalcogenide (TMD) 2D materials.","one_line_summary":"Twisted NbOBr2 van der Waals crystals generate polarization-entangled telecom photons with >95% Bell-state fidelity via SPDC, showing higher brightness than prior TMD-based sources.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The 90° twisted stacking specifically induces the quantum interference responsible for polarization entanglement, rather than arising from other material properties, alignment artifacts, or unaccounted experimental factors.","pith_extraction_headline":"A 90-degree twist in NbOBr2 van der Waals crystals produces polarization-entangled telecom photons with over 95% fidelity."},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":2,"snapshot_sha256":"ac69b2df9e3a8ba0f7c1e702b40ff555b161beb7c848b4584678121f73672881"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}