Fig. 5: Gate-dependent Andreev bound state spectrum.
a Two-tone spectrum at φ = π in a gate voltage range from 0.18 to 0.23 V and from 0.37 to 0.48 V. The phase shift of the resonator δΘ is color coded. The probe frequency is indicated by a dashed black line. We assign the abrupt discontinuities in the state dispersion, e.g., around Vg = 0.43 V, to random reconfigurations of the nanowire surface potential or changes in the effective gate charge. The vertical dashed lines indicate the gate voltages chosen for the flux-dependent measurements discussed later. b Corresponding resonator phase-shift obtained by single-tone spectroscopy in the same gate voltage range. The slight shifts compared to the measurement in a are caused by a time-dependent gate drift.
