  Dispersive charge sensing is realized in hybrid semiconductor-superconductor
nanowires in gate-defined single- and double-island device geometries.
Signal-to-noise ratios (SNRs) were measured both in the frequency and time
domain. Frequency-domain measurements were carried out as a function of
frequency and power and yield a charge sensitivity of $1 \times 10^{-3}
e/\sqrt{\rm Hz}$ for an 11 MHz measurement bandwidth. Time-domain measurements
yield SNR > 1 for 20 $\mu$s integration time. At zero magnetic field,
photon-assisted tunneling was detected dispersively in a double-island
geometry, indicating coherent hybridization of the two superconducting islands.
At an axial magnetic field of 0.6 T, subgap states are detected dispersively,
demonstrating the suitability of the method for sensing in the topological
regime.
