The Quantum Estimation In The Background Of Curved Space-time

With the rapid development of quantum communication,the influence of relativistic effect is inevitable in long-distance quantum communication.The evolution of quantum state in the framework of relativity theory not only has an important influence on long-distance quantum communication,but also has a very positive effect on understanding the two basic theories of quantum mechanics and relativity.Therefore,we mainly study the influence of relativistic effect on quantum Fischer information,and discuss the influence of Unruh effect on the different state parameters.In addition,we also propose an entanglement protection scheme for combating amplitude damping decoherence.The details are as follows:(1)We have investigated how the relativistic effect affect the quantum fisher information and non-locality of the Dirac particles.It has been verified that the QFI with respect to weight parameter ? is independent of the acceleration a when there are inertial observers.Moreover,we also find that for a special multipartite states,|?>1,2,...,N=(cos?|0>(?)N+sin?e1?|1(?)N)the number of particles of the initial state do not affect the QFI F0.Both of these results are meaningful in the practical application.Since quantum information processing is inevitably implemented under the non-inertial frame,moreover,the realization of quantum networks ineluctably need multparticle entangled state,so one can encoded the information on the weight parameter to perform the quantum information task.On the other hand,F? shows a decay behavior with the increase of acceleration a.Similarily,the non-locality also shows a decay behavior with the increase of the acceleration.In addition,the result also shown that in the range of0<???/4,the initial QFI F? is higher when ? is larger,and there exists a more intensive decay in this case.When a particle freely falls in toward a Schwarzschild black hole and locate near the event horizon,the final QFI F? of the initial state is higher than that of the maximally entangled state in the range of arcsin(?)/3<?<?/4.Moreover,the more particles locate near the event horizon,the bigger the interval is.In particular,when two particles locates near the event horizon,the range expands to arcsin(?)/5 ?<?/4.(2)We have also investigated how the Hawking radiation affect the quantum fisher information of the Dirac particles in the background of a Schwarzschild black hole.The results are as follows:The same initial QFI F? is degraded along with two different trajectories except for the maximally entanglement state,the phenomenon just shows the inequivalence of the quantization for the Dirac field in the Schwarzschild and Kruskal space-times.In addition,our results have indicated that the symmetry of the function F? with respect to ? ? ?/4 has been broken due to the influence of the relativistic effect.However,although relativistic effect affects the non-locality of the quantum state,it does not affect its physical structure.(3)In this work,the protection of different quantum entanglement and correlations is explored by local filtering operations.The results show that the filtering operations can indeed be useful for combating amplitude damping decoherence,and recovering the quantum entanglement and correlation.In this scheme,although the final states satisfy the quantum entanglement and correlation,the corresponding initial noisy states does not satisfy them,which means that the filtering operations can reveal the hidden genuine quantum entanglement and correlation of these initial noisy states.