Research On The Key Problems Of Linear Optical Quantum Networks

Quantum networks have attracted much attention because of its potential for quan-tum computation and secure quantum communication.Photons play significant roles in constructing quantum networks because they are relatively free of the decoherence that plagues other quantum systems,and also are easy to be manipulated and detected.Linear optical quantum networks have important applications in quantum information processing,such as quantum key distribution,quantum secret sharing,distributed quan-tum computing and so on.In this paper,based on the linear optical system we study three main aspect of quantum networks:the basic technology of constructing quantum networks,multipartite quantum correlation and the applications of quantum networks.Firstly,we study the basic technology of constructing quantum networks.We demonstrate the all-optical quantum repeater by manipulating twelve photons,and ob-tain a higher entanglement generation rate as compared to the conventional parallel entanglement swapping.Further,to achieve higher distillation efficiency we develop a random entanglement distillation technique for multipartite entangled states in quantum networks.This method help us reduce the waste of entanglement resources.These two technologies are very important for the construction of global quantum networks and will play important roles in the future practical quantum networks.Secondly,we study the multipartite quantum correlation in linear optical networks.We first precisely and systematically infer entanglement structure from the experimental measurement of optimal witnesses.Further,considering the imperfection of practical measurement device,we experimentally identify the multipartite entangled states with a measurement-device-independent entanglement witness and build an open-destination measurement-device-independent quantum network.Moreover,based on the theory of multipartite quantum steering,we develop a new method to identify the number of clas-sical nodes in quantum networks.These studies have important potential applications in the security verification of future quantum networks.Finally,based on the linear optical quantum network,we complete two experi-ments which may have practical applications.By designing a linear optical quantum circuit,we experimentally demonstrate the quantum(3,3)threshold scheme,satisfying the three criteria for the fully quantum secret sharing:reliability,confidentiality,and capability of sharing entangled states.We also experimentally demonstrate the protocol of probabilistic time warp for an uncontrolled photon.It presents a new sight in under-standing the nature of time and has potential application in quantum error correction.