[{"publication":"Journal of Optical Communications and Networking","type":"journal_article","abstract":[{"lang":"eng","text":"<jats:p>\r\n                    The Quantum Internet, a network of quantum-enabled infrastructure, represents the next frontier in telecommunications, promising capabilities that cannot be attained by classical counterparts. A crucial step in realizing such large-scale quantum networks is the integration of entanglement distribution within existing telecommunication infrastructure. Here, we demonstrate a real-world scalable quantum networking testbed deployed within Deutsche Telekom’s metropolitan fibers in Berlin. Using commercially available quantum devices and standard add-drop multiplexing hardware, we distributed polarization-entangled photon pairs over dynamically selectable looped fiber paths ranging from 10 m to 60 km and showed entanglement distribution over up to approximately 100 km. Quantum signals, transmitted at 1324 nm (O-band), coexist with conventional bidirectional C-band traffic without dedicated fibers or infrastructure changes. Active stabilization of the polarization enables robust long-term performance, achieving entanglement Bell-state fidelity bounds between 85% and 99% and Clauser–Horne–Shimony–Holt parameter\r\n                    <jats:italic>S</jats:italic>\r\n                    -values between 2.36 and 2.74 during continuous multiday operation. By achieving a high-fidelity entanglement distribution with less than 1.5% downtime, we confirm the feasibility of hybrid quantum-classical networks under real-world conditions at the metropolitan scale. These results establish deployment benchmarks and provide a practical roadmap for telecom operators to integrate quantum capabilities.\r\n                  </jats:p>"}],"status":"public","_id":"62860","department":[{"_id":"623"},{"_id":"15"}],"user_id":"85353","article_number":"1072","language":[{"iso":"eng"}],"publication_identifier":{"issn":["1943-0620","1943-0639"]},"publication_status":"published","issue":"12","year":"2025","intvolume":"        17","citation":{"apa":"Sena, M., Flament, M., Andrewski, S., Caltzidis, I., Bigagli, N., Rieser, T., Bello Portmann, G., Sekelsky, R., Braun, R.-P., Craddock, A. N., Schulz, M., Jöns, K., Ritter, M., Geitz, M., Holschke, O., &#38; Namazi, M. (2025). High-fidelity quantum entanglement distribution in metropolitan fiber networks with co-propagating classical traffic. <i>Journal of Optical Communications and Networking</i>, <i>17</i>(12), Article 1072. <a href=\"https://doi.org/10.1364/jocn.575396\">https://doi.org/10.1364/jocn.575396</a>","short":"M. Sena, M. Flament, S. Andrewski, I. Caltzidis, N. Bigagli, T. Rieser, G. Bello Portmann, R. Sekelsky, R.-P. Braun, A.N. Craddock, M. Schulz, K. Jöns, M. Ritter, M. Geitz, O. Holschke, M. Namazi, Journal of Optical Communications and Networking 17 (2025).","mla":"Sena, Matheus, et al. “High-Fidelity Quantum Entanglement Distribution in Metropolitan Fiber Networks with Co-Propagating Classical Traffic.” <i>Journal of Optical Communications and Networking</i>, vol. 17, no. 12, 1072, Optica Publishing Group, 2025, doi:<a href=\"https://doi.org/10.1364/jocn.575396\">10.1364/jocn.575396</a>.","bibtex":"@article{Sena_Flament_Andrewski_Caltzidis_Bigagli_Rieser_Bello Portmann_Sekelsky_Braun_Craddock_et al._2025, title={High-fidelity quantum entanglement distribution in metropolitan fiber networks with co-propagating classical traffic}, volume={17}, DOI={<a href=\"https://doi.org/10.1364/jocn.575396\">10.1364/jocn.575396</a>}, number={121072}, journal={Journal of Optical Communications and Networking}, publisher={Optica Publishing Group}, author={Sena, Matheus and Flament, Mael and Andrewski, Shane and Caltzidis, Ioannis and Bigagli, Niccolò and Rieser, Thomas and Bello Portmann, Gabriel and Sekelsky, Rourke and Braun, Ralf-Peter and Craddock, Alexander N. and et al.}, year={2025} }","ama":"Sena M, Flament M, Andrewski S, et al. High-fidelity quantum entanglement distribution in metropolitan fiber networks with co-propagating classical traffic. <i>Journal of Optical Communications and Networking</i>. 2025;17(12). doi:<a href=\"https://doi.org/10.1364/jocn.575396\">10.1364/jocn.575396</a>","ieee":"M. Sena <i>et al.</i>, “High-fidelity quantum entanglement distribution in metropolitan fiber networks with co-propagating classical traffic,” <i>Journal of Optical Communications and Networking</i>, vol. 17, no. 12, Art. no. 1072, 2025, doi: <a href=\"https://doi.org/10.1364/jocn.575396\">10.1364/jocn.575396</a>.","chicago":"Sena, Matheus, Mael Flament, Shane Andrewski, Ioannis Caltzidis, Niccolò Bigagli, Thomas Rieser, Gabriel Bello Portmann, et al. “High-Fidelity Quantum Entanglement Distribution in Metropolitan Fiber Networks with Co-Propagating Classical Traffic.” <i>Journal of Optical Communications and Networking</i> 17, no. 12 (2025). <a href=\"https://doi.org/10.1364/jocn.575396\">https://doi.org/10.1364/jocn.575396</a>."},"publisher":"Optica Publishing Group","date_updated":"2025-12-04T13:37:02Z","volume":17,"date_created":"2025-12-04T12:20:01Z","author":[{"first_name":"Matheus","full_name":"Sena, Matheus","last_name":"Sena"},{"first_name":"Mael","last_name":"Flament","full_name":"Flament, Mael"},{"full_name":"Andrewski, Shane","last_name":"Andrewski","first_name":"Shane"},{"first_name":"Ioannis","full_name":"Caltzidis, Ioannis","last_name":"Caltzidis"},{"last_name":"Bigagli","full_name":"Bigagli, Niccolò","first_name":"Niccolò"},{"first_name":"Thomas","full_name":"Rieser, Thomas","last_name":"Rieser"},{"first_name":"Gabriel","last_name":"Bello Portmann","full_name":"Bello Portmann, Gabriel"},{"last_name":"Sekelsky","full_name":"Sekelsky, Rourke","first_name":"Rourke"},{"last_name":"Braun","full_name":"Braun, Ralf-Peter","first_name":"Ralf-Peter"},{"first_name":"Alexander N.","full_name":"Craddock, Alexander N.","last_name":"Craddock"},{"first_name":"Maximilian","last_name":"Schulz","full_name":"Schulz, Maximilian"},{"first_name":"Klaus","last_name":"Jöns","id":"85353","full_name":"Jöns, Klaus"},{"last_name":"Ritter","full_name":"Ritter, Michaela","first_name":"Michaela"},{"first_name":"Marc","full_name":"Geitz, Marc","last_name":"Geitz"},{"full_name":"Holschke, Oliver","last_name":"Holschke","first_name":"Oliver"},{"first_name":"Mehdi","last_name":"Namazi","full_name":"Namazi, Mehdi"}],"title":"High-fidelity quantum entanglement distribution in metropolitan fiber networks with co-propagating classical traffic","doi":"10.1364/jocn.575396"}]