Manipulation Of Optical Schr?dinger Cat State And Swapping Of Quantum Steering

Quantum information encode,transmission and computation are implemented based on utilizing fundamental principles of quantum mechanics and novel characteristics of quantum systems,such as quantum parallelism,quantum entanglement and quantum nocloning.Quantum information science is able to break through the limit of classical information systems,because of higher capacity of information,information security,computing speed and detection accuracy,which will prompt the development of science and technology and the progress of society.The preparation and manipulation of quantum states are the basics of quantum information science.Quantum information processing could be achieved by manipulating the quantum state using corresponding technology methods.There are many kinds of quantum state,for example,single photon state,entangled photon pairs,squeezed state,entangled state of light,and so on.Different quantum states have different applications,and they can be used to implement different tasks for quantum information processing.Schr?dinger cat states,superposition of two coherent states with same amplitudes but opposite phases,have important significance in exploring fundamental physics problems,for example,experimental demonstration of the Bell inequalities,exploring the boundary between quantum and classical physics,and so on.Meanwhile,Schr?dinger cat states,an important quantum resource,play important roles in quantum information science and quantum metrology.We prepared an optical Schr?dinger cat state and manipulated the amplitude of cat states.These works lay the foundation for applications of optical cat states in quantum information and quantum metrology.EPR steering is another kind of quantum resource for quantum information.In the hierarchy of quantum correlations,EPR steering represents a weaker form of quantum nonlocality and stands between Bell nonlocality and EPR entanglement.Different from entanglement and Bell nonlocality,the asymmetric feature is a unique property of EPR steering.It is necessary to build a quantum information network for practical applications.How to build a quantum steering network? We apply the technology of entanglement swapping to quantum steering and a global quantum network is established by establishing quantum steering between two local quantum networks.The presented schemes provide technical reference for more complicated quantum networks with EPR steering.The completed main research works are as following:1.The second harmonic generation at 397.5 nm for pumping an optical parameter amplifier(OPA)is generated by the method of external frequency doubling.The highefficiency 397.5 nm ultra viola laser was obtained by using nonlinear media,including PPKRP and LBO crystals in the experiment.We obtained-6.0 dB single-mode squeezed vacuum field at 795 nm when the pump power is 120 mW.This is the best result until now at 795 nm.2.The optical Schr?dinger cat state with small size have been prepared experimentally by subtracting a photon from a pure squeezed vacuum state.Then,the amplitude of cat state is amplified and manipulated deterministically by using the second OPA for obtaining the optical cat state with large auplitude.The optical cat state with the amplitude up to 2.07 is obtained experimentally.This work paves the way for applications of optical cat states in quantum information and quantum metrology.3.The technology of Gaussian entanglement swapping is applied for quantum steering.The properties of EPR steering of the state after entanglement swapping between two independent quantum modes without a direct interaction is analyzed theoretically.And this method is extended to construct large-scale multipartite EPR steering network.The presented schemes provide a technical reference for remote quantum communications with EPR steering.The creative works are as follows:1.We prepared optical Schr?dinger cat state at the Rubidium D1 line successfully.The optical cat state with the amplitude up to 2.07 is obtained by an optical parameter amplifier first,and the amplitude of optical Schr?dinger cat state is manipulated deterministically.2.We extended the technology of entanglement swapping to Gaussian quantum steering for the first time,and proposed schemes of Gaussian quantum steering swapping,for two modes and multipartite modes.