  We study quantum state transfer through a qubit network modeled by spins with
XY interaction, when relying on a single excitation. We show that it is
possible to achieve perfect transfer by shifting (adding) energy to specific
vertices. This technique appears to be a potentially powerful tool to change,
and in some cases improve, transfer capabilities of quantum networks.
Analytical results are presented for all-to-all networks and all-to-all
networks with a missing link. Moreover, we evaluate the effect of random
fluctuations on the transmission fidelity.
