  Superconducting resonators enable fast characterization and readout of
mesoscopic quantum devices. Finding ways to perform measurements of interest on
such devices using resonators only is therefore of great practical relevance.
We report the experimental investigation of an InAs nanowire multi-quantum dot
device by probing GHz resonators connected to the device. First, we demonstrate
accurate extraction of the DC conductance from measurements of the
high-frequency admittance. Because our technique does not rely on DC
calibration, it could potentially obviate the need for DC measurements in
semiconductor qubit devices. Second, we demonstrate multiplexed gate sensing
and the detection of charge tunneling on microsecond time scales. The GHz
detection of dispersive resonator shifts allows rapid acquisition of
charge-stability diagrams, as well as resolving charge tunneling in the device
with a signal-to-noise ratio of up to 15 in one microsecond. Our measurements
show that GHz-frequency resonators may serve as a universal tool for fast
tune-up and high-fidelity readout of semiconductor qubits.
