An Ideal Channel of Long Distance Entanglement in Spin Systems

We propose a scheme for using spin chain to realize an ideal channel of long distance entanglement. The results show that there has different entanglement in different Hilbert subspace, the anisotropic parameter $\Delta$ will frustrate the entanglement and the magnetic field affect the entanglement through changing the ground state, the boundary entanglement $C_{1N}$ has the simplest expression in the simplest subspace and it only depend on the first item of the ground state, that item can be increased when a local magnetic field is introduced. Our propose can be handled easily because it only needs a uniform XX open chain initialized in the simplest Hilbert subspace and a bulk magnetic field that absent for the boundary qubits.