  We study the localization of dressed Dirac electrons in a cylindrical quantum
dot (QD) formed on monolayer and bilayer graphene by spatially different
potential profiles. Short lived excitonic states which are too broad to be
resolved in linear spectroscopy are revealed by cross peaks in the photon-echo
nonlinear technique. Signatures of the dynamic gap in the two-dimensional
spectra are discussed. The effect of the Coulomb induced exciton-exciton
scattering and the formation of biexciton molecules are demonstrated.
