preprint draft Thomas Werner author 1fcd8497-dba3-11ea-a45e-c6fbd715f7c70009-0001-2346-5236 Erfan Riyazi author 53322f94-5355-11ee-ae5a-ff6f81c87d51 Samarth Hawaldar author 221708e1-1ff6-11ee-9fa6-85146607433e0000-0002-1965-4309 Rishabh Sahu author 47D26E34-F248-11E8-B48F-1D18A9856A870000-0001-6264-2162 Georg M Arnold author 3770C838-F248-11E8-B48F-1D18A9856A870000-0003-1397-7876 Paul Falthansl-Scheinecker Paul Falthansl-Scheinecker author Jennifer A. Sánchez Naranjo author Dante Loi author Lucky N. Kapoor author Martin Zemlicka author 2DCF8DE6-F248-11E8-B48F-1D18A9856A870009-0005-0878-3032 Liu Qiu author 45e99c0d-1eb1-11eb-9b96-ed8ab2983cac0000-0003-4345-4267 Andrei Militaru author d67706f8-8eb1-11ee-ad1b-9c30dfa19e0b Johannes M Fink author 4B591CBA-F248-11E8-B48F-1D18A9856A870000-0001-8112-028X JoFi department GradSch department Cavity Quantum Electro Optics: Microwave photonics with nonclassical states project Integrated optical coupling for low loss electro-optic interconnects project Quantum Local Area Networks with Superconducting Qubits project Cavity-Integrated Electro-Optics: Measuring, Converting and Manipulating Microwaves with Light project Integrating superconducting quantum circuits project NOMIS Fellowship Program project 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. https://creativecommons.org/licenses/by/4.0/ 2026 eng 2602.0092810.48550/arXiv.2602.00928 https://research-explorer.ista.ac.at/record/21863 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> 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>. 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.). 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> 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>. T. Werner <i>et al.</i>, “Electro-optic conversion of itinerant Fock states,” <i>arXiv</i>. . 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>. 218702026-05-12T13:58:18Z2026-05-20T13:35:42Z