Generation Of Quantum Entangled States Based On Rydberg Atoms And Dissipative Mechanism

For the open system,the coupling between the system and environment is inevitable,which will cause the system decoherence.Such as the atomic spontaneous emission,cavity leakage,and other dissipation process will lead to the decoherence of the quantum states of the system and reduce the validity of quantum information processing.So it is considered as a negative factor of quantum communication and quantum computing.In order to minimize or eliminate the adverse effects of dissipation on the quantum information processing process,especially on the quantum entanglement,which is as an important resource of quantum information,methods such as decoherence-free subspace,quantum error correction,geometric phase,and quantum state purification are usually adopted.However,these methods all take dissipation as a negative factor to overcome.Since Plenio and Cabrillo et al.proposed the pioneering idea of using dissipation as a positive factor to realize quantum entanglement in 1999,there are new ways to realize quantum entanglement and quantum computation.On the other hand,Rydberg atoms is one of the ideal physical systems for quantum information processing due to its large range of adjustable strong interactions and long lifetime of energy levels.In view of this,we mainly explore the preparation of singlet states of three or more Rydberg atoms by means of the strong interaction of Rydberg atoms and atomic spontaneous radiation dissipation channel or partially stimulated adiabatic passage.This research work provides theoretical guidance for the realization of high-dimensional entangled states and useful enlightenment for the utilization of other types of dissipative dynamics.The main contents of the research work are as follows:1.We develop a simple scheme to prepare a steady three-atom singlet state with a dissipative Rydberg pumping process,which combines dissipative dynamics from the the spontaneous emission of Rydberg states and Rydberg interactions.The numerical simulations by master equation show that the fidelity of the created three-atom singlet state can reach up to 0.9947 under certain conditions.The scheme does not require a cavity,initialstate preparation,and exact controlling of operation time,which reduces the difficulty of the experiment.In addition,the experimental feasibility of the scheme is discussed.2.We present a protocol to prepare rapidly a stationary three-atom singlet state with high fidelity,which takes advantage of the dissipative factor originating from the spontaneous emission of short-lived excited states and Rydberg blockade.The short lifetime of the excited states is an active ingredient in the state preparation,and the numerical simulation results of the master equation show that the fidelity of the created state can achieve 0.98 when the evolution time of the system is as short as 300 ?s under certain reasonable conditions.Moreover,the protocol is only weakly dependent on the Rydberg interaction strength and needs no state initialization,optical cavity,feedback controls,and fine controlling of the system parameters,which can greatly reduce the experimental difficulty.3.Combining Rydberg blockade effect and the partially stimulated Raman adiabatic passage,we present a scalable scheme for generating singlet states of Rydberg atoms,where one Rydberg atom is trapped in an optical potential and the others are trapped in the other adjacent optical potential.Moreover,an N-particle N-level singlet state can be generated with the interaction of an N-dimensional Rydberg atom and an(N-1)-atom singlet state.Compared with other schemes,the advantage of our proposal is that no additional quantum storage is required,and an N-particle N-level singlet state with N ? 3 may be realized more simply.