We demonstrate that excited states in single-layer graphene quantum dots can be detected
via direct transport experiments. Coulomb diamond measurements show distinct features of
sequential tunneling through an excited state. Moreover, the onset of inelastic cotunneling in
the diamond region could be detected. For low magnetic fields, the positions of the single-
particle energy levels fluctuate on the scale of a flux quantum penetrating the dot area. For
higher magnetic fields, the transition to the formation of Landau levels is observed …