  We study the evolution with magnetic field of the single-particle energy
levels high up in the energy spectrum of one dot as probed by the ground state
of the adjacent dot in a weakly coupled vertical quantum dot molecule. We find
that the observed spectrum is generally well accounted for by the calculated
spectrum for a two-dimensional elliptical parabolic confining potential, except
in several regions where two or more single-particle levels approach each
other. We focus on two two-level crossing regions which show unexpected
anti-crossing behavior and contrasting current dependences. Within a simple
coherent level mixing picture, we can model the current carried through the
coupled states of the probed dot provided the intrinsic variation with magnetic
field of the current through the states (as if they were uncoupled) is
accounted for by an appropriate interpolation scheme.
