Parametric longitudinal coupling of a semiconductor charge qubit and an rf resonator
V. Champain, Simon Zihlmann, Alessandro Chessari, Benoît Bertrand, Heimanu Niebojewski, Étienne Dumur, X. Jehl, Vivien Schmitt, Boris Brun, Clemens B. Winkelmann, Yann‐Michel Niquet, Michele Filippone, Silvano De Franceschi, Romain Maurand · Physical Review Applied · 2025
In this study, we provide a full experimental characterization of the parametric longitudinal coupling between a complementary metal oxide semiconductor (CMOS) charge qubit and an off-chip rf resonator. Following Corrigan et al., Phys. Rev. Appl. 20, 064005 (2023), we activate parametric longitudinal coupling by driving the charge qubit at the resonator frequency. Managing the crosstalk between the drive applied to the qubit and the resonator allows for the systematic study of the dependence of the longitudinal and dispersive charge-photon couplings on the qubit-resonator detuning and the applied drive. Our experimental estimations of the charge-photon couplings are perfectly reproduced by theoretical simple formulas, without relying on any fitting parameter. We go further by showing a parametric displacement of the resonator's steady state, conditional on the qubit state, and the insensitivity of the longitudinal coupling constant to the photon population of the resonator. Our results pave the way for the exploration of the photon-mediated longitudinal readout and coupling of multiple and distant spins, with long coherent times, in hybrid CMOS circuit quantum electrodynamics architectures.