  The temporal modulation of a relevant parameter can be employed to induce
modal transformations in Hermitian elastic lattices. When this is combined with
a proper excitation mechanism, it allows to drive the energy transfer across
the lattice with tunable propagation rates. Such a modal transformation,
however, is limited by the adiabaticity of the process, which dictates an upper
bound for the modulation speed. In this manuscript, we employ a non-Hermitian
shortcut by way of a tailored gain and loss to violate the adiabatic limit and,
therefore, to achieve superfast modal transformations. A quantitative condition
for adiabaticity is firstly derived and numerically verified for a pair of
weakly coupled time-dependent mechanical oscillators, which can be interpreted
in the light of modal interaction between crossing states. It is shown that for
sufficiently slow time-modulation, the elastic energy can be transferred from
one oscillator to the other. A non-Hermitian shortcut is later induced to break
the modal coupling and, therefore, to speed-up the modal transformation. The
strategy is then generalized to elastic lattices supporting topological edge
states. We show that the requirements for a complete edge-to-edge energy
transfer are lifted from the adiabatic limit toward higher modulation
velocities, opening up new opportunities in the context of wave manipulation
and control.
