  We propose the interaction of two electrons in a triple quantum dot as a
minimal system to control long range superexchange transitions. These are
probed by transport spectroscopy. Narrow resonances appear indicating the
transfer of charge from one side of the sample to the other with the central
one being occupied only virtually. We predict that two different intermediate
states establish the two arms of a one dimensional interferometer.
Configurations of destructive interference of the two superexchage trajectories
totally block the current through the system. We emphasize the role of spin
correlations giving rise to lifetime-enhanced resonances.
