  We investigate superconducting quantum interference devices consisting of two
highly transmissive Josephson junctions coupled by a superconducting loop, all
defined in an epitaxial InAs/Al heterostructure. A novel device design allows
for independent measurements of the Andreev bound state spectrum within the
normal region of a junction and the resulting current-phase relation. We show
that knowledge of the Andreev bound state spectrum alone is enough to derive
the independently measured phase dependent supercurrent. On the other hand, the
opposite relation does not generally hold true as details of the energy
spectrum are averaged out in a critical current measurement. Finally,
quantitative understanding of field dependent spectrum and supercurrent require
taking into account the second junction in the loop and the kinetic inductance
of the epitaxial Al film.
