We study an asymmetric double InGaAs quantum well using optical
two-dimensional coherent spectroscopy. The collection of zero-quantum,
one-quantum, and two-quantum two-dimensional spectra provides a unique and
comprehensive picture of the double well coherent optical response. Coherent
and incoherent contributions to the coupling between the two quantum well
excitons are clearly separated. An excellent agreement with density matrix
calculations reveals that coherent interwell coupling originates from many-body
interactions
