Research On Quantum Steering And Quantum Cryptography

Quantum entanglement and Bell nonlocality,both of which are unique phenomenons of quantum physics different from classical physics,lie in the core of quantum informa-tion theory.As a significant supplement of entanglement and Bell nonlocality,quantum steering builds a bridge between the two concepts.Research on quantum steering cri-teria and the relation between quantum steering and other concepts,has become a hot research area in recent years.As an important application of quantum information the-ory,quantum key distribution(QKD)provides unconditional security based on the prin-ciples of quantum mechanics.However,implementations of QKD face various kinds of attacks,due to imperfections in the experimental devices.Recently,measurement-device-independent quantum key distribution(MDI-QKD)was proposed to close all kinds of detection side-channel attacks.The MDI-QKD is an attractive scheme for prac-tical implementations because of its high security and long transmission distances.This dissertation is based on the results of the author's study and research on quantum steer-ing and quantum cryptography during PhD program.After reviewing quantum steering and quantum cryptography,some new criteria of quantum steering and quantum key distribution protocols are proposed.In the quantum steering criteria's part,a generalized linear criterion and a local-uncertainty-relation based criterion are presented.In comparison with the existing quan-tum steering criterion,the generalized linear criterion and the local-uncertainty-relation based criterion can be applied to a larger range in many cases.An optimization method is developed to reduce the computation complexity for quantum steering criteria,which offers immediate advantages in experimental tests.In addition,relationship between local-uncertainty-relation based criterion and quantum correlation is provided.Further-more,a realignment method for quantum steering and the relationship with the realign-ment method for entanglement is studied.In the QKD's part,a series of researches are made.We have proposed one-sided MDI-QKD protocol,which enjoys detection loophole-free advantage,and at the same time weakens the state preparation assumption in MDI-QKD.For the practical imple-mentation,we also provide a scheme by utilizing coherent light source with an analytical two decoy state estimation method.Simulation with realistic experimental parameters shows that the protocol has a promising performance.For the networking of MDI-QKD,we have proposed an open-destination MDI-QKD network scheme.With our scheme,the secure communication between any two or multiple users can be accomplished un-der assistant of other users in the network.Furthermore,our scheme is secure against untrusted relays and all detector side-channel attacks.In comparison with the existing QKD networks,our scheme provides the future QKD networks with high security and more flexibility.