Spin-chains as quantum channels for qubit-state transfer

In this paper, we provide a simple strategy to optimize the performances of a spin chain as a quantum channel for state transfer. We investigate the most general conditions under which a long range interacting chain achieves the highest fidelity and the shortest transfer time. In this respect, we show that the symmetry of the spin chain plays a key role to identify the ideal system, which involves the sender and receiver only, and provide numerical evidence. However, the two-spin ideal chain is unpractical due to the decrease of the coupling strength with the distance. Therefore we show how to design a spin chain, which nearly approaches the optimal behavior, while keeping the coupling strength reasonably high.