[{"day":"20","intvolume":"        13","date_published":"2026-04-20T00:00:00Z","date_updated":"2026-05-05T12:05:47Z","external_id":{"arxiv":["2511.21819"]},"DOAJ_listed":"1","ddc":["530"],"status":"public","tmp":{"short":"CC BY (4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png"},"department":[{"_id":"OnHo"}],"publication":"Optica","_id":"21747","file":[{"checksum":"f6e62a93f274e0c07197bf4e457eff31","creator":"dernst","date_created":"2026-05-05T12:01:08Z","file_id":"21799","access_level":"open_access","content_type":"application/pdf","file_size":858539,"date_updated":"2026-05-05T12:01:08Z","success":1,"relation":"main_file","file_name":"2026_Optica_Kun.pdf"}],"acknowledgement":"European Union ERC (101071779 (GRAVITES)); European Union Horizon 2020 Research and Innovation Programme (899368 (EPIQUS)); European Union Horizon 2020 Research and Innovation Programme Marie Sklodowska-Curie (956071 (AppQInfo)); European Union HORIZON Europe Research and Innovation Programme (101135288 (EPIQUE)); FWF Austrian Science Fund (10.55776/COE1 (Quantum Science Austria), 10.55776/F71 (BeyondC), 10.55776/FG5 (Research Group 5)); United States Air Force Office of Scientific Research (FA9550-21-1-0355 (Q-Trust), FA8655-23-1-7063 (TIQI)).","OA_place":"publisher","year":"2026","page":"745-751","OA_type":"gold","file_date_updated":"2026-05-05T12:01:08Z","publisher":"Optica Publishing Group","abstract":[{"lang":"eng","text":"Entanglement does not always require one particle per party. It was predicted some 30 years ago that a single photon traversing a beam splitter could violate a Bell inequality. Although initially debated, single-photon nonlocality was eventually demonstrated via homodyne measurements. Here, we present an alternate realization that avoids the complexity of homodyne measurements and potential loopholes in their implementation. We violate a Bell inequality by performing joint measurements on two copies of the same single-photon entangled state, where one photon acts as a phase reference for the other, making it self-referential. We observe CHSH parameters of 2.71 = 0.09 and 2.23 = 0.07, depending on the joint measurements implemented. This offers a perspective on single-photon nonlocality and a more accessible experimental route, potentially applicable to general mode-entangled states in diverse platforms."}],"author":[{"last_name":"Kun","full_name":"Kun, Daniel","first_name":"Daniel"},{"last_name":"Strömberg","id":"68011cd2-da32-11ee-a930-b2774c7aba5f","first_name":"Karl T","full_name":"Strömberg, Karl T"},{"last_name":"Dakić","full_name":"Dakić, Borivoje","first_name":"Borivoje"},{"last_name":"Walther","full_name":"Walther, Philip","first_name":"Philip"},{"last_name":"Rozema","full_name":"Rozema, Lee A.","first_name":"Lee A."}],"doi":"10.1364/OPTICA.586172","date_created":"2026-04-19T22:07:44Z","scopus_import":"1","article_type":"original","arxiv":1,"volume":13,"type":"journal_article","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","PlanS_conform":"1","publication_identifier":{"eissn":["2334-2536"]},"has_accepted_license":"1","oa":1,"oa_version":"Published Version","issue":"4","month":"04","title":"Testing single-photon entanglement using self-referential measurements","language":[{"iso":"eng"}],"publication_status":"published","article_processing_charge":"Yes","quality_controlled":"1","citation":{"ama":"Kun D, Strömberg KT, Dakić B, Walther P, Rozema LA. Testing single-photon entanglement using self-referential measurements. <i>Optica</i>. 2026;13(4):745-751. doi:<a href=\"https://doi.org/10.1364/OPTICA.586172\">10.1364/OPTICA.586172</a>","short":"D. Kun, K.T. Strömberg, B. Dakić, P. Walther, L.A. Rozema, Optica 13 (2026) 745–751.","ista":"Kun D, Strömberg KT, Dakić B, Walther P, Rozema LA. 2026. Testing single-photon entanglement using self-referential measurements. Optica. 13(4), 745–751.","apa":"Kun, D., Strömberg, K. T., Dakić, B., Walther, P., &#38; Rozema, L. A. (2026). Testing single-photon entanglement using self-referential measurements. <i>Optica</i>. Optica Publishing Group. <a href=\"https://doi.org/10.1364/OPTICA.586172\">https://doi.org/10.1364/OPTICA.586172</a>","ieee":"D. Kun, K. T. Strömberg, B. Dakić, P. Walther, and L. A. Rozema, “Testing single-photon entanglement using self-referential measurements,” <i>Optica</i>, vol. 13, no. 4. Optica Publishing Group, pp. 745–751, 2026.","chicago":"Kun, Daniel, Karl T Strömberg, Borivoje Dakić, Philip Walther, and Lee A. Rozema. “Testing Single-Photon Entanglement Using Self-Referential Measurements.” <i>Optica</i>. Optica Publishing Group, 2026. <a href=\"https://doi.org/10.1364/OPTICA.586172\">https://doi.org/10.1364/OPTICA.586172</a>.","mla":"Kun, Daniel, et al. “Testing Single-Photon Entanglement Using Self-Referential Measurements.” <i>Optica</i>, vol. 13, no. 4, Optica Publishing Group, 2026, pp. 745–51, doi:<a href=\"https://doi.org/10.1364/OPTICA.586172\">10.1364/OPTICA.586172</a>."},"project":[{"_id":"bdb108fd-d553-11ed-ba76-83dc74a9864f","name":"QUANTUM INFORMATION SYSTEMS BEYOND CLASSICAL CAPABILITIES / P5- Integration of Superconducting Quantum Circuits","grant_number":"F07105"}]},{"publication":"Physical Review A","department":[{"_id":"OnHo"}],"das_tickbox":"1","day":"16","intvolume":"       111","date_published":"2025-05-16T00:00:00Z","external_id":{"isi":["001501941500006"],"arxiv":["2405.08065"]},"date_updated":"2026-07-07T14:05:51Z","ddc":["530"],"status":"public","tmp":{"short":"CC BY (4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png"},"year":"2025","OA_type":"hybrid","file_date_updated":"2025-05-28T09:16:03Z","publisher":"American Physical Society","abstract":[{"lang":"eng","text":"One of the most striking quantum phenomena is superposition, where one particle simultaneously inhabits different states. Most methods to verify coherent superposition are indirect, in that they require the distinct states to be recombined. Here, we adapt an xor game, in which a “test” photon is placed in a superposition of two orthogonal spatial modes, and each mode is sent to separated parties who perform local measurements on their modes without reinterfering the original modes. We show that by using a second identical “measurement” photon the parties are nonetheless able to verify if the test photon was placed in coherent superposition of the two spatial modes. We then turn this game into a resource-efficient verification scheme, obtaining a confidence that the particle is superposed which approaches unity exponentially fast. We demonstrate our scheme using a single photon, obtaining a 99% confidence that the particle is superposed with only 37 copies. Our work shows the utility of xor games to verify quantum resources, allowing us to efficiently detect quantum superposition without reinterfering the superposed modes."}],"author":[{"last_name":"Kun","full_name":"Kun, Daniel","first_name":"Daniel"},{"last_name":"Strömberg","id":"68011cd2-da32-11ee-a930-b2774c7aba5f","first_name":"Karl T","full_name":"Strömberg, Karl T"},{"last_name":"Spagnolo","first_name":"Michele","full_name":"Spagnolo, Michele"},{"last_name":"Dakić","full_name":"Dakić, Borivoje","first_name":"Borivoje"},{"last_name":"Rozema","first_name":"Lee A.","full_name":"Rozema, Lee A."},{"full_name":"Walther, Philip","first_name":"Philip","last_name":"Walther"}],"article_number":"L050402","_id":"19733","acknowledgement":"This project has received funding from the European Union's Horizon 2020 and Horizon Europe research and innovation programmes under Grant Agreements No. 899368 (EPIQUS) and No. 101135288 (EPIQUE), the Marie Skłodowska-Curie Grant Agreement No. 956071 (AppQInfo), and the QuantERA II Programme under Grant Agreement No. 101017733 (PhoMemtor). The financial support by the Austrian Federal Ministry of Labour and Economy, the National Foundation for Research, Technology and Development, and the Christian Doppler Research Association is gratefully acknowledged. L.A.R. acknowledges support from the Erwin Schrödinger Center for Quantum Science & Technology (ESQ Discovery). This research was funded in whole or in part from the Austrian Science Fund (FWF) through [Grant No. 10.55776/COE1] (Quantum Science Austria), [Grant No. 10.55776/F71] (BeyondC), [Grant No. 10.55776/FG5] (Research Group 5), [Grant No. 10.55776/I6002] (PhoMemtor), and [Grant No. 10.55776/P36994] (Quantum Interference).","file":[{"file_id":"19755","checksum":"b83295a8f597b7781d8e7bfa3b393b42","creator":"dernst","date_created":"2025-05-28T09:16:03Z","file_size":571784,"date_updated":"2025-05-28T09:16:03Z","access_level":"open_access","content_type":"application/pdf","relation":"main_file","success":1,"file_name":"2025_PhysReviewA_Kun.pdf"}],"OA_place":"publisher","researchdata_availability":"yes","user_id":"68b8ca59-c5b3-11ee-8790-cd641c68093d","publication_identifier":{"issn":["2469-9926"],"eissn":["2469-9934"]},"doi":"10.1103/PhysRevA.111.L050402","date_created":"2025-05-25T22:16:54Z","scopus_import":"1","article_type":"letter_note","volume":111,"arxiv":1,"type":"journal_article","publication_status":"published","article_processing_charge":"No","quality_controlled":"1","isi":1,"citation":{"chicago":"Kun, Daniel, Karl T Strömberg, Michele Spagnolo, Borivoje Dakić, Lee A. Rozema, and Philip Walther. “Direct and Efficient Detection of Quantum Superposition.” <i>Physical Review A</i>. American Physical Society, 2025. <a href=\"https://doi.org/10.1103/PhysRevA.111.L050402\">https://doi.org/10.1103/PhysRevA.111.L050402</a>.","mla":"Kun, Daniel, et al. “Direct and Efficient Detection of Quantum Superposition.” <i>Physical Review A</i>, vol. 111, no. 5, L050402, American Physical Society, 2025, doi:<a href=\"https://doi.org/10.1103/PhysRevA.111.L050402\">10.1103/PhysRevA.111.L050402</a>.","ista":"Kun D, Strömberg KT, Spagnolo M, Dakić B, Rozema LA, Walther P. 2025. Direct and efficient detection of quantum superposition. Physical Review A. 111(5), L050402.","ieee":"D. Kun, K. T. Strömberg, M. Spagnolo, B. Dakić, L. A. Rozema, and P. Walther, “Direct and efficient detection of quantum superposition,” <i>Physical Review A</i>, vol. 111, no. 5. American Physical Society, 2025.","apa":"Kun, D., Strömberg, K. T., Spagnolo, M., Dakić, B., Rozema, L. A., &#38; Walther, P. (2025). Direct and efficient detection of quantum superposition. <i>Physical Review A</i>. American Physical Society. <a href=\"https://doi.org/10.1103/PhysRevA.111.L050402\">https://doi.org/10.1103/PhysRevA.111.L050402</a>","short":"D. Kun, K.T. Strömberg, M. Spagnolo, B. Dakić, L.A. Rozema, P. Walther, Physical Review A 111 (2025).","ama":"Kun D, Strömberg KT, Spagnolo M, Dakić B, Rozema LA, Walther P. Direct and efficient detection of quantum superposition. <i>Physical Review A</i>. 2025;111(5). doi:<a href=\"https://doi.org/10.1103/PhysRevA.111.L050402\">10.1103/PhysRevA.111.L050402</a>"},"has_accepted_license":"1","related_material":{"record":[{"relation":"research_data","id":"22142","status":"public"}]},"oa":1,"issue":"5","oa_version":"Published Version","dataavailabilitystatement":"Data that support the findings of this study are openly available at Zenodo.","title":"Direct and efficient detection of quantum superposition","supplementarymaterial":"yes","month":"05","language":[{"iso":"eng"}]},{"doi":"10.1103/xq2l-r4r7","date_created":"2025-12-11T10:46:28Z","volume":24,"arxiv":1,"article_type":"original","scopus_import":"1","type":"journal_article","researchdata_availability":"yes","publication_identifier":{"eissn":["2331-7019"]},"PlanS_conform":"1","user_id":"317138e5-6ab7-11ef-aa6d-ffef3953e345","has_accepted_license":"1","issue":"2","oa_version":"Published Version","oa":1,"dataavailabilitystatement":"The data that support the findings of this article are openly available at https://github.com/hmis4/SurpassingLNTradeOffQKD; https://github.com/hmis4/SurpassingLNTradeOffQKD/tree/main/DomainEngineering  ","title":"Surpassing the loss-noise robustness trade-off in quantum key distribution","month":"08","supplementarymaterial":"no","language":[{"iso":"eng"}],"publication_status":"published","article_processing_charge":"Yes (in subscription journal)","quality_controlled":"1","citation":{"apa":"Seabrook, H., Lavie, E., Strömberg, K. T., Stafford, M. P., &#38; Rubino, G. (2025). Surpassing the loss-noise robustness trade-off in quantum key distribution. <i>Physical Review Applied</i>. American Physical Society. <a href=\"https://doi.org/10.1103/xq2l-r4r7\">https://doi.org/10.1103/xq2l-r4r7</a>","ieee":"H. Seabrook, E. Lavie, K. T. Strömberg, M. P. Stafford, and G. Rubino, “Surpassing the loss-noise robustness trade-off in quantum key distribution,” <i>Physical Review Applied</i>, vol. 24, no. 2. American Physical Society, 2025.","ista":"Seabrook H, Lavie E, Strömberg KT, Stafford MP, Rubino G. 2025. Surpassing the loss-noise robustness trade-off in quantum key distribution. Physical Review Applied. 24(2), 024072.","mla":"Seabrook, Hannah, et al. “Surpassing the Loss-Noise Robustness Trade-off in Quantum Key Distribution.” <i>Physical Review Applied</i>, vol. 24, no. 2, 024072, American Physical Society, 2025, doi:<a href=\"https://doi.org/10.1103/xq2l-r4r7\">10.1103/xq2l-r4r7</a>.","chicago":"Seabrook, Hannah, Emilien Lavie, Karl T Strömberg, Matthew P. Stafford, and Giulia Rubino. “Surpassing the Loss-Noise Robustness Trade-off in Quantum Key Distribution.” <i>Physical Review Applied</i>. American Physical Society, 2025. <a href=\"https://doi.org/10.1103/xq2l-r4r7\">https://doi.org/10.1103/xq2l-r4r7</a>.","ama":"Seabrook H, Lavie E, Strömberg KT, Stafford MP, Rubino G. Surpassing the loss-noise robustness trade-off in quantum key distribution. <i>Physical Review Applied</i>. 2025;24(2). doi:<a href=\"https://doi.org/10.1103/xq2l-r4r7\">10.1103/xq2l-r4r7</a>","short":"H. Seabrook, E. Lavie, K.T. Strömberg, M.P. Stafford, G. Rubino, Physical Review Applied 24 (2025)."},"day":"29","intvolume":"        24","date_published":"2025-08-29T00:00:00Z","external_id":{"arxiv":["2412.08694"]},"date_updated":"2026-07-16T08:27:32Z","tmp":{"short":"CC BY (4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png"},"status":"public","ddc":["530"],"das_tickbox":"1","publication":"Physical Review Applied","department":[{"_id":"OnHo"}],"article_number":"024072","_id":"20797","OA_place":"publisher","acknowledgement":"We thank B. Baragiola, A. Boubriak, M. Clark, M. Jones, and P. Skrzypczyk for useful discussions. H.S. acknowledges financial support from EPSRC Quantum Engineering Centre for Doctoral Training Grant No. EP/SO23607/1. E.L. acknowledges support from the Engineering and Physical Sciences Research Council (EPSRC) Hub in Quantum Computing and Simulation (EP/T001062/1). T.S. acknowledges that they received no funding in support of this research. M.P.S. acknowledges support from the EPSRC Quantum Engineering Centre for Doctoral Training EP/SO23607/1 and the European Commission through Starting Grant No. ERC-2018-STG803665 (PEQEM). G.R. acknowledges support from the Royal Commission for the Exhibition of 1851 through a Research Fellowship, from the European Commission through Starting Grant No. ERC-2018-STG803665 (PEQEM) and Advanced Grant No. ERC-2020-ADG101021085 (FLQuant), and from EPSRC through Standard Proposal Grant No. EP/X016218/1 (Mono-Squeeze).","file":[{"relation":"main_file","success":1,"file_name":"2025_PhysReviewApplied_Seabrook.pdf","file_id":"20824","creator":"dernst","date_created":"2025-12-15T09:39:12Z","checksum":"12ddb0414780f65b8e690fe0e6cfb95e","file_size":3028735,"date_updated":"2025-12-15T09:39:12Z","content_type":"application/pdf","access_level":"open_access"}],"year":"2025","file_date_updated":"2025-12-15T09:39:12Z","OA_type":"hybrid","publisher":"American Physical Society","author":[{"first_name":"Hannah","full_name":"Seabrook, Hannah","last_name":"Seabrook"},{"last_name":"Lavie","full_name":"Lavie, Emilien","first_name":"Emilien"},{"id":"68011cd2-da32-11ee-a930-b2774c7aba5f","last_name":"Strömberg","full_name":"Strömberg, Karl T","first_name":"Karl T"},{"first_name":"Matthew P.","full_name":"Stafford, Matthew P.","last_name":"Stafford"},{"last_name":"Rubino","full_name":"Rubino, Giulia","first_name":"Giulia"}],"abstract":[{"lang":"eng","text":"Quantum key distribution (QKD) offers a theoretically secure method to share secret keys, yet practical implementations face challenges due to noise and loss over long-distance channels. Traditional QKD protocols require extensive noise compensation, hindering their industrial scalability and lowering the achievable key rates. Alternative protocols encode logical qubits in noise-resilient states but at the cost of using many physical qubits, increasing susceptibility to loss and limiting transmission distance. In this work, we introduce a logical-qubit encoding that uses antisymmetric Bell states in the continuous photonic degrees of freedom, frequency and time. By leveraging the continuous space, we overcome this noise-loss robustness trade-off by minimizing the number of photons per logical qubit while optimizing the encoding resilience over noise fluctuations. We analyze the security of our encoding and demonstrate its robustness compared to existing state-of-the-art protocols. This approach provides a path toward scalable, efficient QKD implementations under realistic noise conditions."}]}]