  We study transport mediated by Andreev bound states formed in InSb nanowire
quantum dots. Two kinds of superconducting source and drain contacts are used:
epitaxial Al/InSb devices exhibit a doubling of tunneling resonances, while in
NbTiN/InSb devices Andreev spectra of the dot appear to be replicated multiple
times at increasing source-drain bias voltages. In both devices, a mirage of a
crowded spectrum is created. To describe the observations a model is developed
that combines the effects of a soft induced gap and of additional Andreev bound
states both in the quantum dot and in the finite regions of the nanowire
adjacent to the quantum dot. Understanding of Andreev spectroscopy is important
for the correct interpretation of Majorana experiments done on the same
structures.
