[{"acknowledgement":"The author of this work was supported by the European Research Council under grant no.\r\n101089099 (ERC CoG cQEO) and the European Union’s Horizon 2020 research and innovation\r\nprogram under grant no. 899354 (FETopen SuperQuLAN).\r\nThis work was also supported by the European Research Council under grant nos. 758053\r\n(ERC StG QUNNECT), 101248662 (ERC POC CoupledEOT), and the European Innovation\r\nCouncil no. 101187231 (PathfinderOpen CIELO). This research was funded in whole or in part\r\nby the Austrian Science Fund (FWF) [10.55776/F71]. For open access purposes, the author\r\nhas applied a CC BY public copyright license to any author accepted manuscript version arising\r\nfrom this submission.\r\niii\r\nMy co-authors in the works mentioned later acknowledge generous support from the ISTFELLOW program, the NOMIS-ISTA fellowship, the Horizon Europe Program HORIZONCL4-2022-QUANTUM-01-SGA via Project No. 101113946 OpenSuperQPlus100 and a DOC fellowship of the Austrian Academy of Sciences at IST Austria.\r\n","status":"public","ec_funded":1,"file":[{"checksum":"a5b4d8dba83f96e955a3625c0eebee98","file_name":"2026_Werner_Thomas_Thesis.pdf","content_type":"application/pdf","creator":"twerner","file_id":"21879","relation":"main_file","access_level":"open_access","date_updated":"2026-05-15T15:53:57Z","date_created":"2026-05-15T15:53:57Z","file_size":9330516},{"date_updated":"2026-05-15T15:54:06Z","access_level":"closed","date_created":"2026-05-15T15:54:06Z","file_size":9370704,"creator":"twerner","checksum":"b41282beaacfb32472769b9e3b1758d8","content_type":"application/x-zip-compressed","file_name":"2026_Werner_Thomas_Thesis.zip","relation":"source_file","file_id":"21880"}],"license":"https://creativecommons.org/licenses/by/4.0/","file_date_updated":"2026-05-15T15:54:06Z","alternative_title":["ISTA Thesis"],"publisher":"Institute of Science and Technology Austria","article_processing_charge":"No","_id":"21863","author":[{"last_name":"Werner","full_name":"Werner, Thomas","orcid":"0009-0001-2346-5236","id":"1fcd8497-dba3-11ea-a45e-c6fbd715f7c7","first_name":"Thomas"}],"department":[{"_id":"GradSch"},{"_id":"JoFi"}],"user_id":"8b945eb4-e2f2-11eb-945a-df72226e66a9","date_published":"2026-05-12T00:00:00Z","year":"2026","day":"12","project":[{"_id":"bdadfa0d-d553-11ed-ba76-fb85edbd456a","name":"Cavity Quantum Electro Optics: Microwave photonics with nonclassical states","grant_number":"101089099"},{"_id":"9B868D20-BA93-11EA-9121-9846C619BF3A","name":"Quantum Local Area Networks with Superconducting Qubits","call_identifier":"H2020","grant_number":"899354"},{"grant_number":"758053","_id":"26336814-B435-11E9-9278-68D0E5697425","name":"A Fiber Optic Transceiver for Superconducting Qubits","call_identifier":"H2020"},{"grant_number":"101248662","_id":"5b807754-ab3d-11f0-914f-ff8c34502cc9","name":"Integrated optical coupling for low loss electro-optic interconnects"},{"name":"Cavity-Integrated Electro-Optics: Measuring, Converting and Manipulating Microwaves with Light","_id":"91aaf765-16d5-11f0-9cad-a8e7e44cccb7","grant_number":"101187231"},{"name":"QUANTUM INFORMATION SYSTEMS BEYOND CLASSICAL CAPABILITIES / P5- Integration of Superconducting Quantum Circuits","_id":"bdb108fd-d553-11ed-ba76-83dc74a9864f","grant_number":"F07105"},{"name":"Open Superconducting Quantum Computers (OpenSuperQPlus)","_id":"bdb7cfc1-d553-11ed-ba76-d2eaab167738","grant_number":"101080139"},{"_id":"9B861AAC-BA93-11EA-9121-9846C619BF3A","name":"NOMIS Fellowship Program"}],"type":"dissertation","citation":{"ieee":"T. Werner, “Interfacing superconducting qubits with optical photons,” Institute of Science and Technology Austria, 2026.","apa":"Werner, T. (2026). <i>Interfacing superconducting qubits with optical photons</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT-ISTA-21863\">https://doi.org/10.15479/AT-ISTA-21863</a>","short":"T. Werner, Interfacing Superconducting Qubits with Optical Photons, Institute of Science and Technology Austria, 2026.","chicago":"Werner, Thomas. “Interfacing Superconducting Qubits with Optical Photons.” Institute of Science and Technology Austria, 2026. <a href=\"https://doi.org/10.15479/AT-ISTA-21863\">https://doi.org/10.15479/AT-ISTA-21863</a>.","ama":"Werner T. Interfacing superconducting qubits with optical photons. 2026. doi:<a href=\"https://doi.org/10.15479/AT-ISTA-21863\">10.15479/AT-ISTA-21863</a>","ista":"Werner T. 2026. Interfacing superconducting qubits with optical photons. Institute of Science and Technology Austria.","mla":"Werner, Thomas. <i>Interfacing Superconducting Qubits with Optical Photons</i>. Institute of Science and Technology Austria, 2026, doi:<a href=\"https://doi.org/10.15479/AT-ISTA-21863\">10.15479/AT-ISTA-21863</a>."},"tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","short":"CC BY (4.0)"},"related_material":{"record":[{"relation":"part_of_dissertation","status":"public","id":"19073"},{"relation":"part_of_dissertation","status":"public","id":"21870"}]},"keyword":["Superconducting qubits","Quantum optics","Single photons and quantum effects","Nonlinear optics"],"has_accepted_license":"1","publication_identifier":{"issn":["2663-337X"]},"OA_place":"publisher","doi":"10.15479/AT-ISTA-21863","title":"Interfacing superconducting qubits with optical photons","abstract":[{"lang":"eng","text":"Atoms and photons, two things so different but yet so alike. The former, the building block of matter, something we learn about in school and imagine it as some tiny marbles encircled by other tinier marbles. The latter, an electromagnetic wave, a light particle or an excitation of the electromagnetic field. Quantum mechanics tells us about the properties of these two entities. And even if it sounds, looks and writes counter-intuitive, it has proven right for over a century now.\r\n\r\nIn this work, I elaborate on how we tested the laws of quantum mechanics and how we used them learn more about the tiny building blocks of nature and the fields they use to talk to each other. The atoms we use, are artificial. Superconducting qubits, small electrical circuits with quantized energy levels behave like electrons that transition between different orbitals in an atom. One of the qubits' advantages, is also a big disadvantage. We design the circuits' energy levels and fabricate them in a cleanroom. This allows for arbitrary spaced energy levels but in contrast to real atoms, prevents two superconducting qubits from being alike. Still, this qubit platform is one of the frontrunners for future quantum computing technology and testing fundamental physics due to their scalability.\r\n\r\nWe interface superconducting qubits, which operate in the GHz regime, with microwave photons. We use 3D aluminum cavities as mediators between qubits and photons. The cavities allow for non-destructive readout of the qubit state, they shield the qubits from noise at the qubit frequency and they give us an easy way to frequency-tune these joint systems.\r\n\r\nWe need to operate superconducting qubits and their cavities at millikelvin temperatures in dilution refrigerators. At higher temperatures, superconductivity suffers and even worse, the environment is filled with thermal noise photons. This poses a fundamental limitation on the scalability of superconducting qubit devices. Also connecting multiple devices in different fridges does not work over room temperature links because the microwave photons used for this purpose will be covered in noise and the quantum information they carry, will be unusable.\r\n\r\nInfrared photons do not suffer from this noise problem since there are close to zero thermal noise photons at their frequencies at room temperature. We cannot simply interface superconducting devices with optical photons due their frequency mismatch and the destructive effect of optical photons on superconductors. Therefore, we use microwave-to-optics transducers that allow to convert microwave photons into optical ones and vice-versa. The transducers that we use are macroscopic electro-optic transducers using the Pockels effect in a disk-shaped Lithium Niobate whispering gallery mode resonator. By using a strong optical pump, photons from the two frequency domains experience a beam-splitter interaction and get converted from one to the other.\r\n\r\nWe measure the generated optical photons using elaborate optical setups, optical heterodyning and single photon detectors to gain knowledge about the qubit state or the converted microwave photons. Bridging the microwave and the optical world allows us to take advantage of both of their strengths but it also requires deep knowledge about both of their working principles.\r\n\r\nIn this work, we describe two experiments that our group conducted to showcase the opportunities that arise from interfacing superconducting qubits with optical photons but also the pitfalls, one may encounter on the way.\r\n\r\nIn the first experiment, we managed to all-optically read out a superconducting qubit. We show that the assignment fidelity, the probability that a measurement of the qubit state matches the prepared state, is close to equal for all-optical, microwave-to-optics and conventional microwave readout. We show T1 and T2 measurements for all three readout types and give an analysis of the noise caused by the optics. Finally, we show that the infrared light does not affect the qubit performance in a negative way but that the heating it causes does. This is an important insight that we used in the next experiment.\r\n\r\nThe second experiment is the upconversion of itinerant single microwave photons to the optical domain. We show that we can generate single microwave photons from a qubit-cavity system. We upconvert these single photons, measure them with a single photon detector and reconstruct their shape. By conducting a single photon Rabi measurement, we show correlations between the microwave and the optical domain. And by thorough signal-to-noise measurements and noise analysis, we find that we can generate single infrared photons with high signal-to-noise ratio 5.1 and low transducer added noise (<0.012 quanta). We show that this measurement creates a path towards entanglement of a superconducting qubit and an optical photon and what parameters need to be improved to achieve it. Additionally, this experiment is a proof of principle for an on-demand infrared single photon source. More generally, it allows to link microwave quantum technology in general to the optical domain."}],"acknowledged_ssus":[{"_id":"M-Shop"},{"_id":"NanoFab"},{"_id":"LifeSc"},{"_id":"SSU"}],"degree_awarded":"PhD","publication_status":"published","date_updated":"2026-05-20T13:35:43Z","language":[{"iso":"eng"}],"oa_version":"Published Version","oa":1,"month":"05","ddc":["530","537","539"],"supervisor":[{"orcid":"0000-0001-8112-028X","first_name":"Johannes M","id":"4B591CBA-F248-11E8-B48F-1D18A9856A87","last_name":"Fink","full_name":"Fink, Johannes M"}],"corr_author":"1","date_created":"2026-05-12T09:04:02Z","page":"97"},{"type":"preprint","project":[{"name":"Cavity Quantum Electro Optics: Microwave photonics with nonclassical states","_id":"bdadfa0d-d553-11ed-ba76-fb85edbd456a","grant_number":"101089099"},{"grant_number":"101248662","name":"Integrated optical coupling for low loss electro-optic interconnects","_id":"5b807754-ab3d-11f0-914f-ff8c34502cc9"},{"grant_number":"899354","call_identifier":"H2020","_id":"9B868D20-BA93-11EA-9121-9846C619BF3A","name":"Quantum Local Area Networks with Superconducting Qubits"},{"name":"Cavity-Integrated Electro-Optics: Measuring, Converting and Manipulating Microwaves with Light","_id":"91aaf765-16d5-11f0-9cad-a8e7e44cccb7","grant_number":"101187231"},{"call_identifier":"FWF","_id":"26927A52-B435-11E9-9278-68D0E5697425","name":"Integrating superconducting quantum circuits","grant_number":"F07105"},{"_id":"9B861AAC-BA93-11EA-9121-9846C619BF3A","name":"NOMIS Fellowship Program"}],"tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","short":"CC BY (4.0)"},"OA_type":"green","citation":{"ista":"Werner T, Riyazi E, Hawaldar S, Sahu R, Arnold GM, Paul Falthansl-Scheinecker PF-S, Naranjo JAS, Loi D, Kapoor LN, Zemlicka M, Qiu L, Militaru A, Fink JM. Electro-optic conversion of itinerant Fock states. arXiv, <a href=\"https://doi.org/10.48550/arXiv.2602.00928\">10.48550/arXiv.2602.00928</a>.","ama":"Werner T, Riyazi E, Hawaldar S, et al. Electro-optic conversion of itinerant Fock states. <i>arXiv</i>. doi:<a href=\"https://doi.org/10.48550/arXiv.2602.00928\">10.48550/arXiv.2602.00928</a>","ieee":"T. Werner <i>et al.</i>, “Electro-optic conversion of itinerant Fock states,” <i>arXiv</i>. .","apa":"Werner, T., Riyazi, E., Hawaldar, S., Sahu, R., Arnold, G. M., Paul Falthansl-Scheinecker, P. F.-S., … Fink, J. M. (n.d.). Electro-optic conversion of itinerant Fock states. <i>arXiv</i>. <a href=\"https://doi.org/10.48550/arXiv.2602.00928\">https://doi.org/10.48550/arXiv.2602.00928</a>","chicago":"Werner, Thomas, Erfan Riyazi, Samarth Hawaldar, Rishabh Sahu, Georg M Arnold, Paul Falthansl-Scheinecker Paul Falthansl-Scheinecker, Jennifer A. Sánchez Naranjo, et al. “Electro-Optic Conversion of Itinerant Fock States.” <i>ArXiv</i>, n.d. <a href=\"https://doi.org/10.48550/arXiv.2602.00928\">https://doi.org/10.48550/arXiv.2602.00928</a>.","short":"T. Werner, E. Riyazi, S. Hawaldar, R. Sahu, G.M. Arnold, P.F.-S. Paul Falthansl-Scheinecker, J.A.S. Naranjo, D. Loi, L.N. Kapoor, M. Zemlicka, L. Qiu, A. Militaru, J.M. Fink, ArXiv (n.d.).","mla":"Werner, Thomas, et al. “Electro-Optic Conversion of Itinerant Fock States.” <i>ArXiv</i>, doi:<a href=\"https://doi.org/10.48550/arXiv.2602.00928\">10.48550/arXiv.2602.00928</a>."},"related_material":{"record":[{"id":"21863","relation":"dissertation_contains","status":"public"}]},"main_file_link":[{"open_access":"1","url":"https://doi.org/10.48550/arXiv.2602.00928"}],"acknowledgement":"We thank Fritz Diorico and Onur Hosten who suggested the filter cavity design, and gave important insights about the assembly and the testing of the FabryPerot filter cavities. Ekatrina Fedotova and Diego A.\r\nLancheros Naranjo worked on the filter cavity setup in\r\nthe early stages of this work. Gustavo Wiederhecker and\r\nYiewen Chu provided insights as to the origins of the\r\nobserved optical noise and Nicola Carlon Zambon suggested using telecom filters to mitigate it further. This\r\nwork was supported by the European Research Council under grant agreement no. 101089099 (ERC CoG\r\ncQEO), and 101248662 (ERC POC CoupledEOT), the\r\nEuropean Unions Horizon 2020 research and innovation\r\nprogram under grant agreement no. 899354 (FETopen\r\nSuperQuLAN), the European Innovation Council no.\r\n101187231 (PathfinderOpen CIELO), and the Austrian\r\nScience Fund (FWF) no. F7105 (SFB BeyondC). J.F.\r\nand L.K. acknowledge support from the Horizon Europe\r\nProgram HORIZON-CL4-2022-QUANTUM-01-SGA via\r\nProject No. 101113946 OpenSuperQPlus100. A.M. acknowledges support from the NOMIS-ISTA fellowship.","arxiv":1,"status":"public","ec_funded":1,"_id":"21870","article_processing_charge":"No","author":[{"id":"1fcd8497-dba3-11ea-a45e-c6fbd715f7c7","first_name":"Thomas","orcid":"0009-0001-2346-5236","full_name":"Werner, Thomas","last_name":"Werner"},{"full_name":"Riyazi, Erfan","last_name":"Riyazi","first_name":"Erfan","id":"53322f94-5355-11ee-ae5a-ff6f81c87d51"},{"last_name":"Hawaldar","full_name":"Hawaldar, Samarth","orcid":"0000-0002-1965-4309","id":"221708e1-1ff6-11ee-9fa6-85146607433e","first_name":"Samarth"},{"first_name":"Rishabh","id":"47D26E34-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0001-6264-2162","full_name":"Sahu, Rishabh","last_name":"Sahu"},{"full_name":"Arnold, Georg M","last_name":"Arnold","first_name":"Georg M","id":"3770C838-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0003-1397-7876"},{"full_name":"Paul Falthansl-Scheinecker, Paul Falthansl-Scheinecker","last_name":"Paul Falthansl-Scheinecker","first_name":"Paul Falthansl-Scheinecker"},{"first_name":"Jennifer A. Sánchez","full_name":"Naranjo, Jennifer A. Sánchez","last_name":"Naranjo"},{"first_name":"Dante","last_name":"Loi","full_name":"Loi, Dante"},{"last_name":"Kapoor","full_name":"Kapoor, Lucky N.","first_name":"Lucky N."},{"full_name":"Zemlicka, Martin","last_name":"Zemlicka","id":"2DCF8DE6-F248-11E8-B48F-1D18A9856A87","first_name":"Martin","orcid":"0009-0005-0878-3032"},{"first_name":"Liu","id":"45e99c0d-1eb1-11eb-9b96-ed8ab2983cac","orcid":"0000-0003-4345-4267","full_name":"Qiu, Liu","last_name":"Qiu"},{"last_name":"Militaru","full_name":"Militaru, Andrei","id":"d67706f8-8eb1-11ee-ad1b-9c30dfa19e0b","first_name":"Andrei"},{"full_name":"Fink, Johannes M","last_name":"Fink","id":"4B591CBA-F248-11E8-B48F-1D18A9856A87","first_name":"Johannes M","orcid":"0000-0001-8112-028X"}],"day":"31","year":"2026","date_published":"2026-01-31T00:00:00Z","user_id":"8b945eb4-e2f2-11eb-945a-df72226e66a9","department":[{"_id":"JoFi"},{"_id":"GradSch"}],"oa":1,"corr_author":"1","month":"01","publication":"arXiv","date_created":"2026-05-12T13:58:18Z","doi":"10.48550/arXiv.2602.00928","OA_place":"repository","external_id":{"arxiv":["2602.00928"]},"title":"Electro-optic conversion of itinerant Fock states","abstract":[{"lang":"eng","text":"Superconducting qubits are a leading candidate for utility-scale quantum computing due to their fast gate speeds and steadily decreasing error rates. The requirement for millikelvin operating temperatures, however, creates a significant scaling bottleneck. Modular architectures using optical fiber links could bridge separate cryogenic nodes, but superconducting circuits do not have coherent optical transitions and microwave-to-optical conversion has not been shown for any non-classical photon state. In this work, we demonstrate the on-demand generation and tomographic reconstruction of itinerant single microwave photons at 8.9 GHz from a superconducting qubit. We upconvert this non-Gaussian state with a transducer added noise below 0.012 quanta and count the converted telecom photons at 193.4 THz with a signal-to-noise ratio of up to 5.1$\\pm$1.1. We characterize the trade-offs between throughput and noise, and establish a viable path toward heralded entanglement distribution and gate teleportation. Looking ahead, these results empower existing superconducting devices to take a key role in distributed quantum technologies and heterogeneous quantum systems."}],"publication_status":"draft","date_updated":"2026-05-20T13:35:42Z","scopus_import":"1","oa_version":"Preprint","language":[{"iso":"eng"}]}]