  Quantum communication through spin chains has been extensively investigated.
In this scenario, state transfer through linearly arranged spins connected by
uniform nearest-neighbor couplings qualifies as a natural choice, with minimal
control requirements. However, quantum states usually cannot be perfectly
transferred through a uniformly coupled chain due to the dispersion of the
chain. Here, we propose an effective quantum control technique to realize
almost exact state transfer (AEST) in a quantum spin chain. The strategy is to
add a leakage elimination operator (LEO) Hamiltonian to the evolution, which
implements a sequence of pulse control acting on a perfect state transfer
subspace. By using the one-component Feshbach PQ partitioning technique, we
obtain the conditions over the required pulses. AEST through a spin chain can
then be obtained under a suitable pulse intensity and duration.

Quantum Physics