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Express"],"published-print":{"date-parts":[[2026,7,13]]},"abstract":"<jats:p>\n                    Frequency-degenerate photon pairs generated using nonlinear photonic integrated devices are a crucial resource for scalable quantum information processing and metrology. However, their realization based on dual-pump spontaneous four-wave mixing is hindered by unwanted parametric processes occurring within the same phase matching band, which degrade the signal-to-noise ratio and reduce the purity of the associated quantum states. Here, we propose a dual-pump scheme to produce frequency-degenerate photon pairs, based on cascaded sum-frequency generation and spontaneous parametric down-conversion occurring within a single waveguide, while strongly suppressing parasitic photon pair generation from single-pump processes. This approach significantly simplifies the design compared to microresonator-based methods and enables both pumping and collection of photon pairs entirely in the telecom band. We experimentally validate the concept in a layer-poled thin film lithium niobate waveguide, achieving frequency-degenerate photon pair generation with a brightness of (1.0\u00b10.3)\u00d710\n                    <jats:sup>5<\/jats:sup>\n                    \u2009Hz\u2009nm\n                    <jats:sup>\u22121<\/jats:sup>\n                    \u2009mW\n                    <jats:sup>\u22122<\/jats:sup>\n                    and a 40 dB suppression of unwanted single-pump processes.\n                  <\/jats:p>","DOI":"10.1364\/oe.587612","type":"journal-article","created":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T04:00:06Z","timestamp":1781496006000},"page":"26629","update-policy":"https:\/\/doi.org\/10.1364\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Suppressing parasitic processes in frequency-degenerate photon pair generation via cascaded up- and down-conversion in thin film lithium niobate"],"prefix":"10.1364","volume":"34","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-5958-2882","authenticated-orcid":true,"given":"Olivia","family":"Hefti","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05nrrsx06","id-type":"ROR","asserted-by":"publisher"}]},{"name":"\u00c9cole Polytechnique F\u00e9d\u00e9rale de Lausanne"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4034-4337","authenticated-orcid":true,"given":"Marco","family":"Clementi","sequence":"additional","affiliation":[{"name":"Universit\u00e1 di Pavia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Enrico","family":"Melani","sequence":"additional","affiliation":[{"name":"Universit\u00e1 di Pavia"},{"name":"Norwegian University of Science and Technology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jean-Etienne","family":"Tremblay","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05nrrsx06","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Enlightra"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrea","family":"Volpini","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05nrrsx06","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-3112-7867","authenticated-orcid":true,"given":"Yesim","family":"Koyaz","sequence":"additional","affiliation":[{"name":"\u00c9cole Polytechnique F\u00e9d\u00e9rale de Lausanne"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Homa","family":"Zarebidaki","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05nrrsx06","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ivan","family":"Prieto","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05nrrsx06","id-type":"ROR","asserted-by":"publisher"}]},{"name":"International Iberian Nanotechnology Laboratory (INL)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Olivier","family":"Dubochet","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05nrrsx06","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6506-8485","authenticated-orcid":true,"given":"Daniele","family":"Bajoni","sequence":"additional","affiliation":[{"name":"Universit\u00e1 di Pavia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2735-2423","authenticated-orcid":true,"given":"Charles","family":"Ca\u00e9r","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05nrrsx06","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hamed","family":"Sattari","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05nrrsx06","id-type":"ROR","asserted-by":"publisher"}]},{"name":"CCRAFT"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Camille-Sophie","family":"Br\u00e9s","sequence":"additional","affiliation":[{"name":"\u00c9cole Polytechnique F\u00e9d\u00e9rale de Lausanne"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matteo","family":"Galli","sequence":"additional","affiliation":[{"name":"Universit\u00e1 di 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