Entanglement swapping under global noise environment

We investigate the entanglement swapping under phase damping global noise and amplitude damping global noise. The two qubits the intermediate user holds during the entanglement swapping process first suffer from a global noise before the Bell measurement is carried out. Based on this assumption, the influence of global phase damping noise and global amplitude damping noise on the output entanglement of entanglement swapping is investigated, respectively. Our findings imply that the output entanglement is completely independent of the phase damping global noise and determined by the input entanglement when entanglement swapping is performed in a global phase damping noise environment. In addition, when entanglement swapping is executed in an amplitude damping environment, the output entanglement oscillates periodically with time, and the output entanglement may disappear at some points and reappear at others. In this case, we need not only to improve the input entanglement but also to control the evolution time of the amplitude damping global noise to ensure the optimal output entanglement. Our findings may help experimentalists to avoid and utilize environmental noise in entanglement swapping.