Continuous Variable Quantum State Distributor

Quantum state distributor is one of the most important branches in quantum information processing,it can distribute quantum state from sending nodes to receiving nodes as required.The quantum information encoded in the quantum state is so distributed into the receiving nodes,the distributed information could take part in quantum information processing and quantum computation.Various types of quantum state distributors are proposed to deal with different quantum tasks,the disparities between different distributors are huge.According to the quantity of quantum nodes,quantum state distributors are divided into point-to-point distributors,point-to-multipoint distributors and multipoint-tomultipoint distributors;quantum state distributors are also classified into local distributors and remote distributors according to the distribution distance.The fidelities and the security of quantum state distributor are individual in different quantum state distributors.Usually,many types of distribution are combined in one quantum state distributors to deal with variable quantum tasks.For example,quantum teleportation is point-to-point remote quantum state distributor,while quantum cloning machines can distribute quantum state from one node to many local nodes.There are many ways to realize quantum state distributor,simple distributors with only linear optics devices,and complex distributors also need nonclassical quantum states as the auxiliary resource.Due to the quantum properties of nonclassical quantum state that break classical limits,it can increase the fidelity of the distributed state,distribution distance and the security of the transmitted channel as the auxiliary resource.With the rapidly development of quantum technology,the generation of squeezed states and entangled states is more and more mature.As quantum resource,such nonclassical quantum state can help distributors to distribute quantum state better.Based on the high level nonclassical quantum states,various types of quantum state distributors are realized to deal with the different quantum tasks in this work: high fidelity quantum teleportation;local controllable quantum state distributor;reversible quantum telecloning of continuous variables.The main innovations of this paper are as follow:1.The phase fluctuations of the locking loops in teleportation process is analyzed.The key element effecting on the fidelity is theoretically calculated according to the expression of the two orthogonal quadratures of Einstein-Podolsky-Rosen(EPR)entangled states.Experimental setup for continuous variable quantum teleportation is designed and the theoretical results is demonstrated with experiments.By balancing the extracting loss and phase fluctuations the maximum fidelity of 0.905 is finally obtained,which is the maximum fidelity till now.2.Based on the quantum state transfer with partially disembodied transport proposal,controllable quantum state distributor scheme is proposed and experimentally realized.The fidelities of the quantum state at distributed nodes as a function of the parameter in the distributor is calculated.On the basis,the fidelities at output nodes is manipulated by the distributor to demonstrated the continuous variable controllable quantum state distributor.The information in the transmitted channel is analyzed to illustrate the security of the distributor.Quantum network is also proposed with cascaded quantum state distributor.3.Reversible quantum telecloning of continuous variables is also realized with the help of quadripartite entangled modes,point-to-multipoint remote quantum state distribution is so achieved.In comparison with irreversible quantum telecloning,an extra anti-cloned state is generated without sacrificing the fidelities of two intrinsic cloned states.Such anti-cloned state could distribute quantum information into more quantum nodes and avoid the loss of the quantum information during the telecloning process.Such telecloning may protect the information better against the potential eavesdropping attacks.This work accelerates the application of continuous variable nonclassical state,promotes the development of large-scale quantum network and universal quantum operations.