Semiconductor quantum dot molecules are considered promising
candidates
for quantum technological applications due to their wide tunability
of optical properties and coverage of different energy scales associated
with charge and spin physics. While previous works have studied the
tunnel-coupling of the different excitonic charge complexes shared
by the two quantum dots by conventional optical spectroscopy, we here
report on the first demonstration of a coherently controlled interdot
tunnel-coupling focusing on the quantum coherence of the optically
active trion transitions. We employ ultrafast four-wave mixing spectroscopy
to resonantly generate a quantum coherence in one trion complex, transfer
it to and probe it in another trion configuration. With the help of
theoretical modeling on different levels of complexity, we give an
instructive explanation of the underlying coupling mechanism and dynamical
processes.