  For spins chains to be useful for quantum information processing tasks, the
interaction between the spin chain and its environment generally needs to be
suppressed. In this paper, we propose the use of strong static and oscillating
control fields in order to effectively remove the spin chain-environment
interaction. We find that our control fields can also effectively transform the
spin chain Hamiltonian. In particular, interaction terms which are absent in
the original spin chain Hamiltonian appear in the time-averaged effective
Hamiltonian once the control fields are applied, implying that spin-spin
interactions can be engineered via the application of static and oscillating
control fields. This transformation of the spin chain can then potentially be
used to improve the performance of the spin chain for quantum information
processing tasks. For example, our control fields can be used to achieve almost
perfect quantum state transfer across a spin chain even in the presence of
noise. As another example, we show how the use of particular static and
oscillating control fields not only suppresses the effect of the environment,
but can also improve the generation of two-spin entanglement in the spin chain.
