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arXiv · 2602.00928

Electro-optic conversion of itinerant Fock states

Thomas Werner·Erfan Riyazi·Samarth Hawaldar·Rishabh Sahu·Georg Arnold·Paul Falthansl-Scheinecker·Jennifer A. Sánchez Naranjo·Dante Loi·Lucky N. Kapoor·Martin Zemlicka·Liu Qiu·Andrei Militaru·Johannes M. Fink
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Abstract

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.

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Thomas Werner, Erfan Riyazi, Samarth Hawaldar, Rishabh Sahu, Georg Arnold, Paul Falthansl-Scheinecker, Jennifer A. Sánchez Naranjo, Dante Loi, Lucky N. Kapoor, Martin Zemlicka, Liu Qiu, Andrei Militaru, Johannes M. Fink. 2026-01-31. Electro-optic conversion of itinerant Fock states. https://arxiv.org/abs/2602.00928

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