{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T08:40:15Z","timestamp":1785400815571,"version":"3.56.0"},"reference-count":29,"publisher":"Optica Publishing Group","issue":"15","license":[{"start":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T00:00:00Z","timestamp":1783900800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/doi.org\/10.1364\/OA_License_v2#VOR-OA"},{"start":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T00:00:00Z","timestamp":1783900800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/opg.optica.org\/policies\/opg-tdm-policy.json"}],"funder":[{"DOI":"10.13039\/501100020884","name":"Agencia Nacional de Investigaci\u00f3n y Desarrollo","doi-asserted-by":"crossref","award":["Millennium Science Initiative Program - ICN17_012"],"award-info":[{"award-number":["Millennium Science Initiative Program - ICN17_012"]}],"id":[{"id":"10.13039\/501100020884","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/02ap3w078","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100020884","name":"Agencia Nacional de Investigaci\u00f3n y Desarrollo","doi-asserted-by":"crossref","award":["ANID Anillo ATE250003"],"award-info":[{"award-number":["ANID Anillo ATE250003"]}],"id":[{"id":"10.13039\/501100020884","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/02ap3w078","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100020884","name":"Agencia Nacional de Investigaci\u00f3n y Desarrollo","doi-asserted-by":"crossref","award":["ANID AC3E CIA250006"],"award-info":[{"award-number":["ANID AC3E CIA250006"]}],"id":[{"id":"10.13039\/501100020884","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/02ap3w078","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100020884","name":"Agencia Nacional de Investigaci\u00f3n y Desarrollo","doi-asserted-by":"crossref","award":["2021-22211554"],"award-info":[{"award-number":["2021-22211554"]}],"id":[{"id":"10.13039\/501100020884","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/02ap3w078","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002850","name":"Fondo Nacional de Desarrollo Cient\u00edfico y Tecnol\u00f3gico","doi-asserted-by":"crossref","award":["1240746"],"award-info":[{"award-number":["1240746"]}],"id":[{"id":"10.13039\/501100002850","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/016nafs32","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002850","name":"Fondo Nacional de Desarrollo Cient\u00edfico y Tecnol\u00f3gico","doi-asserted-by":"crossref","award":["1231940"],"award-info":[{"award-number":["1231940"]}],"id":[{"id":"10.13039\/501100002850","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/016nafs32","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002850","name":"Fondo Nacional de Desarrollo Cient\u00edfico y Tecnol\u00f3gico","doi-asserted-by":"crossref","award":["1260111"],"award-info":[{"award-number":["1260111"]}],"id":[{"id":"10.13039\/501100002850","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/016nafs32","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002850","name":"Fondo Nacional de Desarrollo Cient\u00edfico y Tecnol\u00f3gico","doi-asserted-by":"crossref","award":["1240843"],"award-info":[{"award-number":["1240843"]}],"id":[{"id":"10.13039\/501100002850","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/016nafs32","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002850","name":"Fondo Nacional de Desarrollo Cient\u00edfico y Tecnol\u00f3gico","doi-asserted-by":"crossref","award":["3210359"],"award-info":[{"award-number":["3210359"]}],"id":[{"id":"10.13039\/501100002850","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/016nafs32","id-type":"ROR","asserted-by":"publisher"}]},{"name":"University of Concepci\u00f3n","award":["UCO 1866"],"award-info":[{"award-number":["UCO 1866"]}],"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Ministerio de Ciencia, Innovaci\u00f3n y Universidades","award":["CEX2019-000910-S"],"award-info":[{"award-number":["CEX2019-000910-S"]}],"id":[{"id":"https:\/\/ror.org\/05r0vyz12","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Ministerio de Ciencia, Innovaci\u00f3n y Universidades","award":["PRTR-C17.I1"],"award-info":[{"award-number":["PRTR-C17.I1"]}],"id":[{"id":"https:\/\/ror.org\/05r0vyz12","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Ministerio de Ciencia, Innovaci\u00f3n y Universidades","award":["FUNQIP"],"award-info":[{"award-number":["FUNQIP"]}],"id":[{"id":"https:\/\/ror.org\/05r0vyz12","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003593","name":"Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100003593","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/03swz6y49","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000780","name":"European Commission","doi-asserted-by":"crossref","award":["Horizon Europe \/ MSCA grant number 101081441"],"award-info":[{"award-number":["Horizon Europe \/ MSCA grant number 101081441"]}],"id":[{"id":"10.13039\/501100000780","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/00k4n6c32","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":["opg.optica.org"],"crossmark-restriction":false},"short-container-title":["Opt. Express"],"published-print":{"date-parts":[[2026,7,27]]},"abstract":"<jats:p>\n                    Inter-core skew (ICS), the differential group delay between cores of a multicore fiber (MCF), is a critical parameter for both classical space-division multiplexed communications and quantum photonic networks. We present a high-precision measurement of ICS in commercially available four-core fibers using two-photon Hong\u2013Ou\u2013Mandel (HOM) interference in a fiber-integrated 4\u2009\u00d7\u20094 multiport beam splitter, using both photon pairs from spontaneous parametric down-conversion (SPDC) and a weak-coherent-state source (a bimodal pulsed laser). By extracting the center position of HOM interference dips and peaks across all twelve core-pair combinations, we obtain individual ICS values whose precision is limited by the delay-stage positioning uncertainty. This first multi-length characterization of RMS ICS, spanning laboratory to field-deployed scales, finds results consistent with the expected\n                    <jats:italic>L<\/jats:italic>\n                    stochastic random-walk scaling,\n                    <jats:italic>\u03c3<\/jats:italic>\n                    <jats:sub>\n                      <jats:italic>\u03c4<\/jats:italic>\n                    <\/jats:sub>\n                    (\n                    <jats:italic>L<\/jats:italic>\n                    )=\n                    <jats:italic>\u03ba<\/jats:italic>\n                    <jats:italic>L<\/jats:italic>\n                    +\n                    <jats:italic>c<\/jats:italic>\n                    with intrinsic coefficient\n                    <jats:italic>\u03ba<\/jats:italic>\n                    =(39.80\u00b10.003)\n                    <jats:italic>ps<\/jats:italic>\n                    \/\n                    <jats:italic>km<\/jats:italic>\n                    . This measurement was made possible by HOM\u2019s immunity to first-order path fluctuations, which render classical interferometric methods impractical for long installed fibers. The demonstrated \u00b10.11\u2005ps precision for the two-photon interference represents a \u223c180-fold improvement over correlation optical time-domain reflectometry (C-OTDR), the standard method for long-fiber ICS characterization. Fisher information analysis establishes a fundamental Cram\u00e9r\u2013Rao precision limit in the few-femtosecond range, indicating further improvement is achievable with better delay control. The SPDC source provides this precision on laboratory-testbed fibers, while the weak-coherent-state source trades precision for loss tolerance, extending the measurement to a 1300\u2005m field-deployed fiber with &gt;10\u2009dB losses. These results establish a practical platform for characterizing timing uniformity in MCF-based networks for both quantum and classical space-division multiplexed applications.\n                  <\/jats:p>","DOI":"10.1364\/oe.601686","type":"journal-article","created":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T09:00:07Z","timestamp":1781686807000},"page":"26981","update-policy":"https:\/\/doi.org\/10.1364\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Sub-picosecond inter-core skew characterization in multicore fibers via Hong\u2013Ou\u2013Mandel interference"],"prefix":"10.1364","volume":"34","author":[{"given":"L. Lira","family":"Tacca","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"L. Marques","family":"Fagundes","sequence":"additional","affiliation":[{"name":"Universidade Federal de Santa Catarina"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M.","family":"Morales Lillo","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M.","family":"Navarro","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]},{"name":"The Barcelona Institute of Science and Technology"},{"name":"Luxquanta Technologies S.L., Av. Joan Carles I, 30, 1o1a. 08908 L\u2019Hospitalet de Llobregat"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"I.","family":"Machuca","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S.","family":"G\u00f3mez","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Sapienza Universit\u00e1 di Roma"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0389-1430","authenticated-orcid":true,"given":"G. H.","family":"dos Santos","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6232-6012","authenticated-orcid":true,"given":"J.","family":"Cari\u00f1e","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5450-3661","authenticated-orcid":true,"given":"G.","family":"Saavedra","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3227-9432","authenticated-orcid":true,"given":"E. S.","family":"G\u00f3mez","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"G.","family":"Lima","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3346-8625","authenticated-orcid":true,"given":"S. P.","family":"Walborn","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0460jpj73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"285","published-online":{"date-parts":[[2026,7,13]]},"reference":[{"key":"oe-34-15-26981-R1","doi-asserted-by":"publisher","first-page":"354","DOI":"10.1038\/nphoton.2013.94","type":"journal-article","volume":"7","author":"Richardson","year":"2013","journal-title":"Nat. Photonics"},{"key":"oe-34-15-26981-R2","doi-asserted-by":"publisher","first-page":"55","DOI":"10.1109\/JLT.2015.2466444","type":"journal-article","volume":"34","author":"Saitoh","year":"2016","journal-title":"J. Lightwave Technol."},{"key":"oe-34-15-26981-R4","doi-asserted-by":"publisher","first-page":"5291","DOI":"10.1109\/JLT.2019.2931987","type":"journal-article","volume":"37","author":"Alfredsson","year":"2019","journal-title":"J. Lightwave Technol."},{"key":"oe-34-15-26981-R6","doi-asserted-by":"publisher","first-page":"980","DOI":"10.1109\/JLT.2022.3195190","type":"journal-article","volume":"41","author":"Takeshita","year":"2023","journal-title":"J. Lightwave Technol."},{"key":"oe-34-15-26981-R7","doi-asserted-by":"publisher","first-page":"108","DOI":"10.1038\/s44172-026-00664-x","type":"journal-article","volume":"5","author":"Chen","year":"2026","journal-title":"Commun. Eng."},{"key":"oe-34-15-26981-R9","doi-asserted-by":"publisher","first-page":"034024","DOI":"10.1103\/PhysRevApplied.15.034024","type":"journal-article","volume":"15","author":"G\u00f3mez","year":"2021","journal-title":"Phys. Rev. Appl."},{"key":"oe-34-15-26981-R10","doi-asserted-by":"publisher","first-page":"040356","DOI":"10.1103\/PRXQuantum.2.040356","type":"journal-article","volume":"2","author":"Ortega","year":"2021","journal-title":"PRX Quantum"},{"key":"oe-34-15-26981-R11","doi-asserted-by":"publisher","first-page":"022317","DOI":"10.1103\/PhysRevA.96.022317","type":"journal-article","volume":"96","author":"Ca nas","year":"2017","journal-title":"Phys. Rev. A"},{"key":"oe-34-15-26981-R12","doi-asserted-by":"publisher","first-page":"8081","DOI":"10.1364\/OE.24.008081","type":"journal-article","volume":"24","author":"Dynes","year":"2016","journal-title":"Opt. Express"},{"key":"oe-34-15-26981-R13","doi-asserted-by":"publisher","first-page":"9","DOI":"10.1038\/s42005-019-0269-7","type":"journal-article","volume":"3","author":"Xavier","year":"2020","journal-title":"Commun. Phys."},{"key":"oe-34-15-26981-R14","doi-asserted-by":"publisher","first-page":"542","DOI":"10.1364\/OPTICA.388912","type":"journal-article","volume":"7","author":"Cari ne","year":"2020","journal-title":"Optica"},{"key":"oe-34-15-26981-R15","doi-asserted-by":"publisher","first-page":"026113","DOI":"10.1063\/5.0308068","type":"journal-article","volume":"11","author":"Nakamura","year":"2026","journal-title":"APL Photonics"},{"key":"oe-34-15-26981-R16","doi-asserted-by":"publisher","first-page":"2250","DOI":"10.1109\/LPT.2017.2771248","type":"journal-article","volume":"29","author":"Lee","year":"2017","journal-title":"IEEE Photonics Technol. Lett."},{"key":"oe-34-15-26981-R18","doi-asserted-by":"publisher","first-page":"3579","DOI":"10.1364\/AO.457156","type":"journal-article","volume":"61","author":"Jin","year":"2022","journal-title":"Appl. Opt."},{"key":"oe-34-15-26981-R19","doi-asserted-by":"publisher","first-page":"12555","DOI":"10.1364\/OE.23.012555","type":"journal-article","volume":"23","author":"Lee","year":"2015","journal-title":"Opt. Express"},{"key":"oe-34-15-26981-R20","doi-asserted-by":"publisher","first-page":"2044","DOI":"10.1103\/PhysRevLett.59.2044","type":"journal-article","volume":"59","author":"Hong","year":"1987","journal-title":"Phys. Rev. Lett."},{"key":"oe-34-15-26981-R21","doi-asserted-by":"publisher","first-page":"024028","DOI":"10.1103\/PhysRevApplied.14.024028","type":"journal-article","volume":"14","author":"Aguilar","year":"2020","journal-title":"Phys. Rev. Appl."},{"key":"oe-34-15-26981-R22","doi-asserted-by":"publisher","first-page":"021801","DOI":"10.1103\/PhysRevA.81.021801","type":"journal-article","volume":"81","author":"Aboussouan","year":"2010","journal-title":"Phys. Rev. A"},{"key":"oe-34-15-26981-R23","doi-asserted-by":"publisher","first-page":"013830","DOI":"10.1103\/PhysRevA.91.013830","type":"journal-article","volume":"91","author":"Gerrits","year":"2015","journal-title":"Phys. Rev. A"},{"key":"oe-34-15-26981-R24","doi-asserted-by":"publisher","first-page":"022804","DOI":"10.1063\/1.5048537","type":"journal-article","volume":"4","author":"Puttnam","year":"2019","journal-title":"APL Photonics"},{"key":"oe-34-15-26981-R25","author":"Saleh","year":"2019"},{"key":"oe-34-15-26981-R26","doi-asserted-by":"publisher","first-page":"1029","DOI":"10.1049\/el:19860703","type":"journal-article","volume":"22","author":"Poole","year":"1986","journal-title":"Electron. Lett."},{"key":"oe-34-15-26981-R27","doi-asserted-by":"publisher","first-page":"687","DOI":"10.1364\/OL.13.000687","type":"journal-article","volume":"13","author":"Poole","year":"1988","journal-title":"Opt. Lett."},{"key":"oe-34-15-26981-R28","doi-asserted-by":"publisher","first-page":"060807","DOI":"10.1103\/jy6g-jp7n","type":"journal-article","volume":"136","author":"Descamps","year":"2026","journal-title":"Phys. Rev. Lett."},{"key":"oe-34-15-26981-R29","doi-asserted-by":"publisher","first-page":"063715","DOI":"10.1103\/PhysRevA.106.063715","type":"journal-article","volume":"106","author":"Jordan","year":"2022","journal-title":"Phys. Rev. A"},{"key":"oe-34-15-26981-R30","author":"Kay","year":"1993"},{"key":"oe-34-15-26981-R31","doi-asserted-by":"publisher","first-page":"193603","DOI":"10.1103\/PhysRevLett.132.193603","type":"journal-article","volume":"132","author":"Meskine","year":"2024","journal-title":"Phys. Rev. Lett."},{"key":"oe-34-15-26981-R33","doi-asserted-by":"publisher","first-page":"172","DOI":"10.1038\/s41534-021-00502-2","type":"journal-article","volume":"7","author":"Cari ne","year":"2021","journal-title":"npj Quantum Information"},{"key":"oe-34-15-26981-R35","doi-asserted-by":"publisher","first-page":"2504","DOI":"10.1364\/OL.596451","type":"journal-article","volume":"51","author":"Gao","year":"2026","journal-title":"Opt. Lett."}],"container-title":["Optics Express"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/opg.optica.org\/viewmedia.cfm?URI=oe-34-15-26981&seq=0","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T19:10:17Z","timestamp":1783969817000},"score":1,"resource":{"primary":{"URL":"https:\/\/opg.optica.org\/abstract.cfm?URI=oe-34-15-26981"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,13]]},"references-count":29,"journal-issue":{"issue":"15","published-online":{"date-parts":[[2026]]},"published-print":{"date-parts":[[2026]]}},"URL":"https:\/\/doi.org\/10.1364\/oe.601686","relation":{},"ISSN":["1094-4087"],"issn-type":[{"value":"1094-4087","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,13]]},"assertion":[{"value":"Optica Publishing Group","name":"publisher","label":"This article is maintained by"},{"value":"https:\/\/doi.org\/10.1364\/OE.601686","name":"articlelink","label":"Crossref DOI link to publisher maintained version"},{"value":"research-article","name":"content_type","label":"Article type"},{"value":"Screened by Similarity Check","name":"cross_check","label":"Similarity check"},{"value":"Yes","order":0,"name":"peer_reviewed","label":"Peer reviewed","group":{"name":"peer_review","label":"Peer review"}},{"value":"Single blind","order":1,"name":"review_process","label":"Review process","group":{"name":"peer_review","label":"Peer review"}},{"value":"15 April 2026","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"9 June 2026","order":1,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"13 July 2026","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}},{"value":"\u00a9 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement","name":"copyright","label":"Copyright"}]}}