{
  "abstract": "We experimentally demonstrate the generation of needle-like beams from spontaneous parametric downconversion (SPDC) light using a compact inverse-designed multilevel diffractive lens (MDL). The nonclassical nature of the SPDC source is independently verified through a three-detector heralded Hanbury Brown-Twiss measurement performed before the MDL, yielding a zero-delay second-order correlation value of approximately 0.14. Spatial measurements using an intensified charge-coupled device reveal that the MDL maintains a tightly confined focal distribution over an axial distance of approximately 11 mm under collinear SPDC illumination, substantially reducing diffraction-induced broadening compared with a conventional plano-convex lens of the same nominal focal length. Under non-collinear SPDC illumination, two distinct regions of extended axial confinement are observed, demonstrating the dependence of the engineered focal distribution on the incident spatial field. These results establish a compact flat-optical approach for engineering extended-focus SPDC photon fields, with potential applications in structured quantum photonics.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.02993",
  "author_total": 7,
  "authors": [
    {
      "name": "Sunny"
    },
    {
      "name": "Jyotshna Bora"
    },
    {
      "name": "Ayush Tiwari"
    },
    {
      "name": "C. S. Yadav"
    },
    {
      "name": "Rajesh Menon"
    },
    {
      "name": "Amit D. Lad"
    },
    {
      "name": "Vishwa Pal"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8mtn3swqvxpd9.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.02993",
  "fulltext_url": null,
  "id": "8mtn3swqvxpd9",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.02993",
  "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",
      "quant-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.02993",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8mtn3swqvxpd9.ris",
  "sources": [
    {
      "first_seen": "2026-11-03T12:20:59Z",
      "native_id": "2611.02993",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.02993"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Needle-beam generation from SPDC photons using inverse-designed flat optics",
  "title_text": "Needle-beam generation from SPDC photons using inverse-designed flat optics",
  "type": "preprint",
  "updated_at": "2026-11-05T15:20:18Z",
  "url": "https://research.draconitic.com/paper/8mtn3swqvxpd9",
  "venue": "arXiv",
  "versions": []
}