article published yes Franco De Palma author Fabian Oppliger author Wonjin Jang author Stefano Bosco author Marian Janik author 396A1950-F248-11E8-B48F-1D18A9856A870009-0003-9037-8831 Stefano Calcaterra author Georgios Katsaros author 38DB5788-F248-11E8-B48F-1D18A9856A870000-0001-8342-202X Giovanni Isella author Daniel Loss author Pasquale Scarlino author GeKa department Towards scalable hut wire quantum devices project High impedance circuit quantum electrodynamics with hole spins project Semiconductor quantum dots (QDs) in planar germanium (Ge) heterostructures have emerged as front-runners for future hole-based quantum processors. Here, we present strong coupling between a hole charge qubit, defined in a double quantum dot (DQD) in planar Ge, and microwave photons in a high-impedance (Zr = 1.3 kΩ) resonator based on an array of superconducting quantum interference devices (SQUIDs). Our investigation reveals vacuum-Rabi splittings with coupling strengths up to g0/2π = 260 MHz, and a cooperativity of C ~ 100, dependent on DQD tuning. Furthermore, utilizing the frequency tunability of our resonator, we explore the quenched energy splitting associated with strong Coulomb correlation effects in Ge QDs. The observed enhanced coherence of the strongly correlated excited state signals the presence of distinct symmetries within related spin functions, serving as a precursor to the strong coupling between photons and spin-charge hybrid qubits in planar Ge. This work paves the way towards coherent quantum connections between remote hole qubits in planar Ge, required to scale up hole-based quantum processors. https://research-explorer.ista.ac.at/download/18602/18611/2024_NatureComm_dePalma.pdf application/pdfno Springer Nature2024 eng 2041-1723 39580488 00136268420000110.1038/s41467-024-54520-7 15 F. De Palma <i>et al.</i>, “Strong hole-photon coupling in planar Ge for probing charge degree and strongly correlated states,” <i>Nature Communications</i>, vol. 15. Springer Nature, 2024. De Palma, F., Oppliger, F., Jang, W., Bosco, S., Janik, M., Calcaterra, S., … Scarlino, P. (2024). Strong hole-photon coupling in planar Ge for probing charge degree and strongly correlated states. <i>Nature Communications</i>. Springer Nature. <a href="https://doi.org/10.1038/s41467-024-54520-7">https://doi.org/10.1038/s41467-024-54520-7</a> De Palma F, Oppliger F, Jang W, Bosco S, Janik M, Calcaterra S, Katsaros G, Isella G, Loss D, Scarlino P. 2024. Strong hole-photon coupling in planar Ge for probing charge degree and strongly correlated states. Nature Communications. 15, 10177. F. De Palma, F. Oppliger, W. Jang, S. Bosco, M. Janik, S. Calcaterra, G. Katsaros, G. Isella, D. Loss, P. Scarlino, Nature Communications 15 (2024). De Palma, Franco, Fabian Oppliger, Wonjin Jang, Stefano Bosco, Marian Janik, Stefano Calcaterra, Georgios Katsaros, Giovanni Isella, Daniel Loss, and Pasquale Scarlino. “Strong Hole-Photon Coupling in Planar Ge for Probing Charge Degree and Strongly Correlated States.” <i>Nature Communications</i>. Springer Nature, 2024. <a href="https://doi.org/10.1038/s41467-024-54520-7">https://doi.org/10.1038/s41467-024-54520-7</a>. De Palma, Franco, et al. “Strong Hole-Photon Coupling in Planar Ge for Probing Charge Degree and Strongly Correlated States.” <i>Nature Communications</i>, vol. 15, 10177, Springer Nature, 2024, doi:<a href="https://doi.org/10.1038/s41467-024-54520-7">10.1038/s41467-024-54520-7</a>. De Palma F, Oppliger F, Jang W, et al. Strong hole-photon coupling in planar Ge for probing charge degree and strongly correlated states. <i>Nature Communications</i>. 2024;15. doi:<a href="https://doi.org/10.1038/s41467-024-54520-7">10.1038/s41467-024-54520-7</a> 186022024-12-01T23:01:53Z2025-09-08T14:46:06Z