Longitudinal coupling between a Si/SiGe quantum dot and an off-chip TiN resonator

Superconducting cavities have emerged as a key tool for measuring the spin states of quantum dots. So far however, few experiments have explored longitudinal couplings between dots and cavities, and no solid-state qubit experiments have explicitly probed the "adiabatic" regime, where the Purcell decay is strongly suppressed. Here, we report measurements of a quantum-dot hybrid qubit coupled to a high-impedance resonator via a "flip-chip" design geometry. By applying an ac drive to the qubit through two different channels, and studying the effects of qubit energy detuning and interdot tunneling, we are able to unequivocally confirm the presence of a longitudinal coupling between the qubit and cavity. Since this coupling is proportional to the driving amplitude, and is therefore switchable, it has the potential to become a powerful new tool in qubit experiments.