Study Of Entanglement, Impurity And Decoherence In Heisenberg Spin Chain

In this paper, the impact of the impurity on the entanglement between spins in a Heisenberg spin chain is investigated. The dynamical evolution of the entanglement is discussed.The zero-temperature pairwise entanglement in an antiferromagnetic Heisenberg spin-1/2 chain is investigated when one impure spin s (s≥1) is added in the system. The pairwise entanglement is proportional to 1/s when the spin impurity is located at one end of the open three-qubit spin chain. This means that the entanglement will disappear and finally approach to the classical continuous system as s→∞. The pairwise entanglement is calculated when the impurity is located at a mediate site of the spin chain. Compared to the isotropic Heisenberg spin-1/2 chain without impurity, the closest pairwise entanglement can be obviously enhanced. The effective control of the spin coupling between the impurity spin and nearest-neighbor spins can enhance the pairwise entanglement.The dynamical evolution of the next-nearest-neighbor entanglement is investigated in an open frustrated three-qubit Heisenberg spin chain when the frustrated interaction coefficient is varied. Compared to the closed uniform interacted spin system, the state swapping between two spins will occur in the frustrated spin chain. The entanglement is distinctly increased with the increase of the frustrated interaction coefficient. If the system is in a vacuum reservoir, the introduced collective spontaneous emission due to the strong dipole-dipole interactions can lead the oscillations of the entanglement to approach a stable value when the spontaneous decay rate is fixed. The stable value will increase with increasing the collective spontaneous emission rate.