  A measure for the maximum quantum information transfer capacity (ITC) between
nodes of a spin network is defined, and shown to induce a metric on a space of
equivalence classes of nodes for homogeneous chains with XX and Heisenberg
couplings. The geometry and curvature of spin chains with respect of this
metric are studied and compared to the physical network geometry. For general
networks hierarchical clustering is used to elucidate the proximity of nodes
with regard to the maximum ITC. Finally, it is shown how minimal control can be
used to overcome intrinsic limitations and speed up information transfer.
