Quantum Information In Noninertial Frame And Curved Spacetime

The integration of the quantum information and general relativity, as well as string theory, thermodynamics and statistics, gives birth to the theory of the relativistic quantum information. Doubtlessly, the research of quantum informa-tion in a relativistic setting will not only provide a more complete framework for the quantum information theory, but also play an important role in the under-standing of the entropy and information paradox of black holes. It is well known that the real world is essentially noninertial, i. e., the real world inevitably exists acceleration and rotation. Thus, related research is also closely related to the im-plementation of quantum computation with observers in arbitrary relative motion and the study of the physical bounds of quantum information processing tasks. This thesis is devoted to the investigation of bipartite and multipartite quantum entanglement, classical and quantum correlations, as well as system-environment dynamics in noninertial frames and curved spacetimes. Some interesting results are obtained:The classical and quantum correlation sharing between modes of Dirac fields in the noninertial frame are investigated. It is shown that (ⅰ) the classical correlation for the Dirac fields decreases as the acceleration increases, which is different from the result in a scalar field, where the classical correlation is independent of the acceleration;(ⅱ) there is no simple dominating relation between the quantum correlation and entanglement or the Dirac fields, which is unlike the scalar case, where the quantum correlation is always over and above the entanglement;(ⅲ) as the acceleration increases, the correlations between modes Ⅰand Ⅱand between modes A and Ⅱ increase, but the correlations between modes A and Ⅰdecrease.The bipartite and tripartite entanglement of a3-qubit fermionic system when one or two subsystems accelerated are also investigated,(ⅰ) It is shown that all the one-tangles decrease as the acceleration increases. However, unlike the scalar case, here one-tangles NcI(ABI) and NcI(AB) never reduce to zero for any acceleration.(ⅱ) It is found that the system has only tripartite entanglement when either one or two subsystems accelerated, which means that the acceleration doesn't gener-ate bipartite entanglement and doesn't effect the entanglement structure of the quantum states in this system.(ⅲ) It is interesting to note that the π-tangle of the two-observers-accelerated case decreases much quicker than that of the one-observcr-aceelerated case and it reduces to a non-zero minimum in the infinite acceleration limit. Thus we argue that multipartite systems are better than bi-partite systems to perform quantum information processing tasks in noninertial systems.Besides, we study the decoherence in a noninertial frame for the first time. It is shown that the decoherence and loss of the entanglement generated by Unruh effect will influence each other remarkably. It is interesting to note that in the case of the total system under decoherence, the sudden death of the entanglement could appear for any acceleration. However, in the case of only Rob's qubit under deco-herence, the sudden death could only take place when the acceleration parameter is greater than a "critical point". In addition, the system-environment dynamics of noninertial systems is investigated. It is shown that (ⅰ) for the amplitude damping channel the thermal fields generated by the Unruh effect can promote the sudden death of entanglement between the subsystems while postpone the sudden birth of entanglement between the environments;(ⅱ) there is no system-environment and environment-environment entanglements when the system coupled with the phase damping environment;(ⅲ) the form of initial state plays an important role in the system-environment dynamics of entanglement in noninertial frames.Finally, the effect of Hawking radiation on the entanglement redistribution in the Schwarzschild spacetime has been investigated. Our analysis shows that, due to the initial entanglement described by inertial observers is redistributed between all the bipartite modes, the physically accessible entanglement degrades while the unaccessible entanglement increases as the Hawking temperature increases. We also find that the physically accessible mutual information becomes smaller while the unaccessible mutual information increases as the Hawking temperature in-creases. It is interesting to note that the accessible mutual information equals to just half of its initial value, and the unaccessible mutual information between mode A and in also equals to the same value when the temperature turns to infinity.