  Using a global optimization algorithm we obtain spin chains with
site-dependent exchange coefficients which allow almost perfect quantum state
transfer between the extremes of the chains without any further time-dependent
external control. We consider chains with isotropic and anisotropic Heisenberg
Hamiltonian with up to 100 spins. The method allow us to choose the arrival of
the transferred state by changing the range available to the exchange coupling
strengths. We consider short transferred times, in particular shorter than
those achievable with known time-dependent control schemes. The chains obtained
with the optimization method show some remarkable and interesting traits as,
for instance, the scaling of the magnitude of the exchange couplings needed to
achieve near perfect state transfer with the length of the chain and the
arrival time. This scaling makes it possible to decide if the chain with
site-dependent coefficients can be implemented in an actual system according to
the range of interactions allowed in it. We compare the robustness of the
transmission protocol against static disorder on the exchange coefficients
using different figures of merit, which allow us to conclude that the isotropic
Heisenberg chain is the best option when compared with anisotropic chains. This
comparison is relevant since the method allow us to start with chains that all
achieve near perfect quantum state transfer, regime that was not available
previously in these chains without time-dependent external control.
