The swap operation in the two-qubit Heisenberg XXZ model-effects of   anisotropy and magnetic field
  In this paper we study the swap operation in a two-qubit anisotropic XXZ model in the presence of an inhomogeneous magnetic field. We establish the range of anisotropic parameter within which the swap operation is feasible. The swap errors caused by the inhomogeneous field are evaluated. 
Yue Zhou, Guo-Feng Zhang, Fu-Hua Yang and Song-Lin Feng