  The possibility of using quantum computers for electronic structure
calculations has opened up a promising avenue for computational chemistry.
Towards this direction, numerous algorithmic advances have been made in the
last five years. The potential of quantum annealers, which are the prototypes
of adiabatic quantum computers, is yet to be fully explored. In this work, we
demonstrate the use of a D-Wave quantum annealer for the calculation of excited
electronic states of molecular systems. These simulations play an important
role in a number of areas, such as photovoltaics, semiconductor technology and
nanoscience. The excited states are treated using two methods, time-dependent
Hartree-Fock (TDHF) and time-dependent density-functional theory (TDDFT), both
within a commonly used Tamm-Dancoff approximation (TDA). The resulting TDA
eigenvalue equations are solved on a D-Wave quantum annealer using the Quantum
Annealer Eigensolver (QAE), developed previously. The method is shown to
reproduce a typical basis set convergence on the example H$_2$ molecule and is
also applied to several other molecular species. Characteristic properties such
as transition dipole moments and oscillator strengths are computed as well.
Three potential energy profiles for excited states are computed for NH$_3$ as a
function of the molecular geometry. Similar to previous studies, the accuracy
of the method is dependent on the accuracy of the intermediate meta-heuristic
software called qbsolv.
