Experimental Study Of Multiplexing Quantum Key Distribution And Classical Optical Communications

Quantum key distribution(QKD)supplies information-theoretic security based on the principles of quantum mechanics.Since its introduction in 1984,QKD has undergone dramatic progress from point-to-point experiments to QKD network implementations.Due to its extremely low intensity,conventional QKD signals require an exclusive fibre link dedicated to its transmission.To avoid the high cost of laying extra fibre,the integration of QKD with conventional telecom fibre channels is of great importance.This thesis is mainly about the wavelength division multiplexing(WDM)between QKD and classical optical communications,describes the realization of a series of WDM experiments that I involved and led.With multistage band-stop filtering techniques,we maintain sufficient isolation among the quantum channel,the synchronous channel and the classical channels,and propose a multiplexing scheme realizing the integration of QKD and bidirectional FP laser communications.Moreover,this scheme enables QKD over fiber lengths of up to 45 km.By means of wavelength selecting and spectral and temporal filtering,we realize the multiplexing and long distance co-propagation of QKD and Terabit classical coherent optical communication system up to 80 km.Our demonstration verifies the feasibility of QKD and classical communication to share the resources of backbone fibre links,and thus take the utility of QKD a great step forward.With proper classical launch power,we demonstrate that QKD can be deployed in GPON networks with up to 64 users and provide high security applications at low costs.Besides,this thesis describes the experimental realization of QKD with public-key authentication.We construct a TCP/IP protocol port based on FPGA to exchange authentication data and results between QKD system and rainbow algorithm program in computer.By developing interfering two independent lasers and up-conversion single-photon detectors,we faithfully demonstrate the measurement-device-independent quantum-key-distribution protocol,which is immune to all hacking strategies on detection.Our practical system generates more than 25 kbit secure key over a 50 km fiber link,serves as a stepping stone in the quest for unconditionally secure communications with realistic devices.We simulate and optimize the secure key rate of efficient BB84 scheme when implemented in our QKD system.Compared with standard BB84 protocol,the efficient scheme can drastically improve the secure key rates.We construct a phase-modulated polarization-encoding system to test the efficient scheme.