Entanglement dynamics of two qubits coupled by Heisenberg XY interaction under a nonuniform magnetic field in a spin bath

This paper investigates the entanglement dynamics of a Heisenberg XY model for a two-spin system in the presence of a nonuniform magnetic field. The master equations and the concurrence evolution equations for the initial α state ave derived and analysed. It is shown that for the symmetric initial α state, only the nonuniform field can play a role in entanglement dynamics while the uniform field and the bath will not play such a role. For the asymmetric α state, the nonuniform field leads to the beat pattern oscillation of the concurrence evolution. The inhomogeneity of the field can enhance the entanglement by suppressing the decoherence effects of both the spin-orbit interaction and the spin bath.