Experimental characterization of the qubit-mediated coupling between two waveguides
Abstract
We report the first experimental realization and comprehensive characterization of a system consisting of two spatially separated superconducting waveguides coupled via a single transmon qubit. Since this system enables coherent control and the exchange of microwave photons between waveguides, and also holds the potential to serve as a scalable basic unit in quantum routing architectures, we will henceforth refer to it as a basic cell. The cell was characterized at 10 mK with an average input signal of ≈1 photon at ≈6 GHz, and with the qubit biased to its optimal point to minimize sensitivity to external magnetic fluctuations. By combining steady-state and time-domain measurements, we reconstructed the key parameters of the system, including qubit relaxation and dephasing, waveguide-qubit couplings, and cross-waveguide photon transfer efficiency. The observed performance is consistent with a non-Hermitian Hamiltonian formalism and demonstrates clear limits set by flux bias, temperature, and photon number, in agreement with flux- and temperature-induced dephasing models. Crucially, the cell operates reliably at the low-photon level, and in the high-photon regime we directly observe photon dressing induced by the qubit. These results establish a versatile platform for studying open quantum system phenomena and pave the way for scalable implementations of quantum routing and network nodes.
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BibTeX
@article{mutsenik2026experimental,
title = {{Experimental characterization of the qubit-mediated coupling between two waveguides}},
author = {Evgeniya Mutsenik and Aidar Sultanov and Leonie Kaczmarek and Matthias Schmelz and Gregor Oelsner and Ronny Stolz and Evgeni Il’ichev},
journal = {npj Quantum Information},
year = {2026},
month = oct,
doi = {10.1038/s41534-026-01399-5},
url = {https://www.nature.com/articles/s41534-026-01399-5},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Experimental characterization of the qubit-mediated coupling between two waveguides
AU - Evgeniya Mutsenik
AU - Aidar Sultanov
AU - Leonie Kaczmarek
AU - Matthias Schmelz
AU - Gregor Oelsner
AU - Ronny Stolz
AU - Evgeni Il’ichev
PY - 2026
DA - 2026/10/29
JO - npj Quantum Information
DO - 10.1038/s41534-026-01399-5
UR - https://www.nature.com/articles/s41534-026-01399-5
AB - We report the first experimental realization and comprehensive characterization of a system consisting of two spatially separated superconducting waveguides coupled via a single transmon qubit. Since this system enables coherent control and the exchange of microwave photons between waveguides, and also holds the potential to serve as a scalable basic unit in quantum routing architectures, we will henceforth refer to it as a basic cell. The cell was characterized at 10 mK with an average input signal of ≈1 photon at ≈6 GHz, and with the qubit biased to its optimal point to minimize sensitivity to external magnetic fluctuations. By combining steady-state and time-domain measurements, we reconstructed the key parameters of the system, including qubit relaxation and dephasing, waveguide-qubit couplings, and cross-waveguide photon transfer efficiency. The observed performance is consistent with a non-Hermitian Hamiltonian formalism and demonstrates clear limits set by flux bias, temperature, and photon number, in agreement with flux- and temperature-induced dephasing models. Crucially, the cell operates reliably at the low-photon level, and in the high-photon regime we directly observe photon dressing induced by the qubit. These results establish a versatile platform for studying open quantum system phenomena and pave the way for scalable implementations of quantum routing and network nodes.
SN - 2056-6387
ER -