The Experimental Research On Measurement-device-independent Quantum Key Distribution System And Network

Quantum key distribution(QKD)allows the unconditional secure key generation by the laws of quantum physics.Since the appearance of BB84 protocol in 1984,QKD has been gradually developed into a practical networked system with high secure key rate through long communication distance.Accompany with the development of real QKD systems,people pay much attention to the security issue of them.The practical QKD systems suffer from various loopholes rooted in their deviations from the theoretical models.Nowadays,we have found many security loopholes.Some loopholes have been used to implement the effective attack towards real QKD systems.Therefore,only if the security loopholes of real QKD systems are eliminated,we can achieve the real unconditional security of QKD.The measurement-device-independent QKD(MDI-QKD)protocol eliminates the detection related loopholes by assigning the measurement to an untrusted third party(Charlie).It is of great importance to promote the security of practical QKD systems.However,the experiments of MDI-QKD appear to be complex,which is an obstacle to real applications.In this dissertation,we study the experimental demonstration of the polarization discriminated time-bin phase-encoding MDI-QKD system,the plug-and-play MDI-QKD system,and the plug-and-play MDI-QKD network.The main results are listed as following:1.We make a proof-of-principle demonstration of the polarization discriminated time-bin phase-encoding MDI-QKD.Our system needs fewer intensity modulator than other systems,and can collect all coincidences effectively.The polarization modulator,together with an asymmetric Mach-Zehnder interferometer which is composed of two polarization beam splitters(PBSs),are used to generate the encoding states of MDI-QKD.The time-bin 0 and time-bin 1 are multiplexed with the polarization states of H and V.The optical intensity of Z basis are in accordance with that of X basis.At the detection site,Charlie makes use of two PBSs to demultiplex the polarization states,and implements the partial Bell state measurement(BSM).2.We make a proof-of-principle demonstration of a self-stabilized asymmetric plugand-play MDI-QKD.Alice and Bob share a homemade signal laser and an AMZI which are in the charge of Charlie.There is no mismatch in pulse waveform,optical spectral,phase-reference-frame,and polarization state at all.A passive timing calibration method is developed to ensure the precise and stable interference of signal pulses from Alice and Bob.The SynL pulses of Alice(Bob)are used to drive the signal laser to generate the signal pulses of Bob(Alice).Our system reduces the hardware requirements for Alice and Bob significantly.3.We propose an overal design of the plug-and-play MDI-QKD network.The untrusted server charges all assistant systems,including the measurement system,the synchronization system,and the signal-laser system.The users only need to monitor and modulate the signals received.Each synchronization laser is assigned to an identified user.The user can encode the signals inspired by other synchronization lasers subsequently to realize a point-to-multipoint communication.Finally,we make a proof-ofprinciple demonstration of a self-stabilized plug-and-play MDI-QKD network.There are three users(Alice,Bob,and David)and one untrusted server.By modulating the signals belonging to Alice and Bob subsequently,David can communicate with Alice and Bob simultaneously.It is convenient to realize a large MDI-QKD network by adding more users.