preprint draft Marian Janik author 396A1950-F248-11E8-B48F-1D18A9856A870009-0003-9037-8831 Kevin Etienne Robert Roux author 53f93ea2-803f-11ed-ab7e-b283135794ef Carla N Borja Espinosa author 18777c01-896a-11ed-bdf8-e4851dc07d16 Oliver Sagi author 71616374-A8E9-11E9-A7CA-09ECE5697425 Abdulhamid Baghdadi author 160D87FA-96B5-11E9-BF77-7626E6697425 Thomas Adletzberger author 38756BB2-F248-11E8-B48F-1D18A9856A87 Stefano Calcaterra author Marc Botifoll author Alba Garzón Manjón author Jordi Arbiol author Daniel Chrastina author Giovanni Isella author Ioan M. Pop author Georgios Katsaros author 38DB5788-F248-11E8-B48F-1D18A9856A870000-0001-8342-202X GeKa department GradSch department JoFi department Integrated Germanium Quantum Technology project Towards scalable hut wire quantum devices project Merging spin and superconducting qubits in planar Ge project High impedance circuit quantum electrodynamics with hole spins project High kinetic inductance superconductors are gaining increasing interest for the realisation of qubits, amplifiers and detectors. Moreover, thanks to their high impedance, quantum buses made of such materials enable large zero-point fluctuations of the voltage, boosting the coupling rates to spin and charge qubits. However, fully exploiting the potential of disordered or granular superconductors is challenging, as their inductance and, therefore, impedance at high values are difficult to control. Here we have integrated a granular aluminium resonator, having a characteristic impedance exceeding the resistance quantum, with a germanium double quantum dot and demonstrate strong charge-photon coupling with a rate of $g_\text{c}/2\pi= (566 \pm 2)$ MHz. This was achieved due to the realisation of a wireless ohmmeter, which allows \emph{in situ} measurements during film deposition and, therefore, control of the kinetic inductance of granular aluminium films. Reproducible fabrication of circuits with impedances (inductances) exceeding 13 k$\Omega$ (1 nH per square) is now possible. This broadly applicable method opens the path for novel qubits and high-fidelity, long-distance two-qubit gates. https://creativecommons.org/licenses/by/4.0/ 2024 eng 2407.0307910.48550/arXiv.2407.03079 https://research-explorer.ista.ac.at/record/18886 https://research-explorer.ista.ac.at/record/19401 https://research-explorer.ista.ac.at/record/18129 Janik M, Roux KER, Borja Espinosa CN, Sagi O, Baghdadi A, Adletzberger T, Calcaterra S, Botifoll M, Manjón AG, Arbiol J, Chrastina D, Isella G, Pop IM, Katsaros G. Strong charge-photon coupling in planar germanium enabled by granular  aluminium superinductors. arXiv, 2407.03079. M. Janik <i>et al.</i>, “Strong charge-photon coupling in planar germanium enabled by granular  aluminium superinductors,” <i>arXiv</i>. . Janik, Marian, Kevin Etienne Robert Roux, Carla N Borja Espinosa, Oliver Sagi, Abdulhamid Baghdadi, Thomas Adletzberger, Stefano Calcaterra, et al. “Strong Charge-Photon Coupling in Planar Germanium Enabled by Granular  Aluminium Superinductors.” <i>ArXiv</i>, n.d. <a href="https://doi.org/10.48550/arXiv.2407.03079">https://doi.org/10.48550/arXiv.2407.03079</a>. Janik M, Roux KER, Borja Espinosa CN, et al. Strong charge-photon coupling in planar germanium enabled by granular  aluminium superinductors. <i>arXiv</i>. doi:<a href="https://doi.org/10.48550/arXiv.2407.03079">10.48550/arXiv.2407.03079</a> Janik, Marian, et al. “Strong Charge-Photon Coupling in Planar Germanium Enabled by Granular  Aluminium Superinductors.” <i>ArXiv</i>, 2407.03079, doi:<a href="https://doi.org/10.48550/arXiv.2407.03079">10.48550/arXiv.2407.03079</a>. M. Janik, K.E.R. Roux, C.N. Borja Espinosa, O. Sagi, A. Baghdadi, T. Adletzberger, S. Calcaterra, M. Botifoll, A.G. Manjón, J. Arbiol, D. Chrastina, G. Isella, I.M. Pop, G. Katsaros, ArXiv (n.d.). Janik, M., Roux, K. E. R., Borja Espinosa, C. N., Sagi, O., Baghdadi, A., Adletzberger, T., … Katsaros, G. (n.d.). Strong charge-photon coupling in planar germanium enabled by granular  aluminium superinductors. <i>arXiv</i>. <a href="https://doi.org/10.48550/arXiv.2407.03079">https://doi.org/10.48550/arXiv.2407.03079</a> 181442024-09-26T09:50:43Z2026-07-16T22:30:50Z