Preparation Of Distributed Quantum Entanglement Under The Dissipation Mechanism

Dissipation has been conventionally considered as a detrimental factor traditionally because it would destroy the unitary dynamics and induce decoherence.The quest to find viable strategies for avoiding decoherence is an essential issue for the development of quantum technologies.For the cavity quantum electrodynamics system,the typical dissipative factors that induce the decoherence including atomic spontaneous emission process,cavity leakage process and so on.Recently,a new strategy has been put forward:the dissipative processes can act as an prerequisite for the implementation of quantum information processing,transforming the detrimental dissipative factors of system into positive factors.Such as preparation of entangled quantum state with atom-cavity systems and solid state systems.This is different from traditional ideas.By means of an reasonably engineered interaction of the system with its environment,dissipative process can not perturb unitary dynamics.Strictly speaking,the relationship between unitary dynamics and the dissipative process can be interpreted as unity of opposites between competition and cooperation,which jointly drives the system to stabilization.The main purpose of this dissertation is to design schemes which utilize the dissipative processes in the spatially separated cavities to prepare distributed entanglement.We hope that the theoretical considerations can offer convenience and supporting theories for the experimental works.We propose two schemes for preparing the distributed steady-state entanglement of two atoms trapped in separate optical cavities coupled through an optical fiber and coupled to each other directly based on the cooperation and competition behavior of the unitary dynamics and dissipative process.In these two schemes,only the atom of one node is driven by external classical fields.This greatly simplify the experimental implementation due to the unilateral manipulation on one node and the process of entanglement distribution can be avoided.Hence,the absolute security of long distance quantum information processing tasks can be guaranteed.Furthermore,based on the dissipative entanglement preparation scheme,we construct quantum teleportation setup with multiple nodes as practical application,and the numerical simulation demonstrates the scheme can be realized effectively under the current experimental conditions.In the separately coupled cavities,we propose a scheme to prepare entanglement in which the atomic spontaneous emission and cavity decay are used as necessary resources.The combination of coherent driving fields and dissipative processes will drive the system into a steady state.By choosing different frequency of classical laser field,the target steady state can be generated in different ways.The numerical simulation shows that the target state with high fidelity and purity can be produced and does not require specifying the initial states and controlling evolution time accurately.Since the detrimental dissipative factors are used as resources,our scheme has lower requirement about the quality factor of the optical cavity.In the three separate optical cavities that are coupled to each other through two optical fibers,we propose a scheme to generate long distance three atomic entanglement based on coherent driving and dissipation,which are induced by the classical fields and the decay of non-local bosonic modes,respectively.In our scheme,the interaction time need not be controlled strictly in the overall dynamics processes,and the cavity field decay can be changed into a vital resource.The numerical simulation shows that the fidelity of the target state is insensitive to effective atomic spontaneous emission.In addition,the present scheme can also be generalized to prepare the N-partite W state of distant atoms.A dissipation-based scheme is proposed to prepare the adjustable steady entangled state of two spatially separated nitrogen-vacancy(NV)centers fixed on the exterior surface of two microtoroidal resonators coupled by the whispering-gallery-mode(WGM)field.The effective operator method is used to get an effective master equation which simplifies the systematic dynamics into ground state subspace.Based on the effective dynamics,the parameter condition to use the NV center's spontaneous emission and that to use resonator's photon loss as resources to prepare entanglement are achieved,respectively.Interestingly,we find that these two conditions are almost the same as each other.In some extent,these two dissipative factors can be used as powerful resources to prepare the steady entangled state simultaneously.On the other hand,the form of the target state is adjustable via modulating systematic parameters.Numerical results show that high fidelity and purity can be achieved and the scheme is robust on small parameter deviations.