Dynamic generation of entangling wave packets in XY spin system with decaying long-range couplings

The dynamic generation of spin entanglement between two distant sites in a XY model with 1/r ² decay long-range couplings was studied. Due to the linear dispersion relation ε(k)∼|k| of magnons in such a model, a well-located spin state can be dynamically split into two moving entangled local wave packets without changing their shapes. Interestingly, when such two wave packets meet at the diametrically opposite site after the fast period τ = Nπ/J, the initial well-located state is completely recurrent. Numerical calculation was performed to confirm the analytical result even if the ring system of sizes N up to several thousands is considered. The truncation approximation for the coupling strengths was also studied. Numerical simulation shows that the above conclusions still hold even if the range of the coupling strength is truncated to a relatively short scale compared with the size of the spin system. Supported by the National Natural Science Foundation of China (Grant Nos. 90203018, 10474104 and 60433050) and the National Fundamental Research Program of China (Grant Nos. 2001CB309310 and 2005CB724508)