  Spin qubits in germanium are a promising contender for scalable quantum
computers. Reading out of the spin and charge configuration of quantum dots
formed in Ge/Si core/shell nanowires is typically performed by measuring the
current through the nanowire. Here, we demonstrate a more versatile approach on
investigating the charge configuration of these quantum dots. We employ a
high-impedance, magnetic-field resilient superconducting resonator based on
NbTiN and couple it to a double quantum dot in a Ge/Si nanowire. This allows us
to dispersively detect charging effects, even in the regime where the nanowire
is fully pinched off and no direct current is present. Furthermore, by
increasing the electro-chemical potential far beyond the nanowire pinch-off, we
observe indications for depleting the last hole in the quantum dot by using the
second quantum dot as a charge sensor. This work opens the door for dispersive
readout and future spin-photon coupling in this system.
