  We unravel the nonequilibrium quantum dynamics of two harmonically confined
bosons in one spatial dimension when performing an interaction quench from
finite repulsive to attractive interaction strengths and vice versa. A closed
analytical form of the expansion coefficients of the time-evolved two-body
wavefunction is derived, while its dynamics is determined in terms of an
expansion over the postquench eigenstates. For both quench scenarios the
temporal evolution is analyzed by inspecting the one- and two-body reduced
density matrices and densities, the momentum distribution and the fidelity.
Resorting to the fidelity spectrum and the eigenspectrum we identify the
dominant eigenstates of the system that govern the dynamics. Monitoring the
dynamics of the above-mentioned observables we provide signatures of the
energetically higher-lying states triggered by the quench.
