(color online) (a) Conductance G of a second device as a function of back gate voltage V_g measured at T = 10 mK with an ac bias V_ac = 100 µeV. A small magnetic field B = 30 mT is applied to suppress superconductivity in the Al contacts. Green and orange squares mark the regions to be discussed hereinbelow. (b) Differential conductance dI/dV as a function of bias voltage V_sd and gate voltage V_g, corresponding to the same range denoted by the green square in panel (a). The nonlinear transport spectroscopy shows a characteristic Fabry–Pérot interference pattern, providing direct experimental evidence for ballistic charge transport through InSb nanowires.