  Recently, the terahertz (THz) photon-assisted tunneling (PAT) through a
two-level InAs quantum dot (QD) has been successfully realized in experiment
[Phys. Rev. Lett. {\bf 109}, 077401 (2012)]. The Coulomb interaction in this
device is comparable with the energy difference between the two energy levels.
We theoretically explore the effects of Coulomb interaction on the PAT
processes and show that the main peaks of the experiment can be well derived by
our model analysis. Furthermore, we find additional peaks, which were not
addressed in the InAs QD experiment and may be further identified in
experiments. In particular, we show that, to observe the interesting
photon-induced excited state resonance in InAs QD, the Coulomb interaction
should be larger than THz photon frequency.
