  The use of quantum computing to solve a problem in quantum mechanics is
illustrated, step by step, by calculating energies and transition amplitudes in
a nonrelativistic quark model. The quantum computations feature the use of
variational quantum imaginary time evolution implemented using automatic
differentiation to determine ground and excited states of charmonium. The
calculation of transition amplitudes is illustrated utilizing the Hadamard
test. Examples of readout and gate error mitigation are included.
