Research Of Practical Challenge During Quantum Communication Processing

In 1984,the first quantum key distribution(QKD)protocol proposed by Bennett and Brassard(BB84)widens our horizon for cryptography systems.With several assumptions,i.e.ideal single photon source,lossless transmission,perfect preparation and measurement,QKD has been proved unconditional security.Since so far those assumptions are unreachable,extensive theoretic and experimental studies has been implemented to improve the performance of QKD systems.The first two parts of this article introduced the basic theory and basic protocol of quantum key distribution.The basic theory includes two parts:cryptography and basic theory of quantum mechanics.Cryptography started from its development,introduced quantum cryptography,and introduced why quantum cryptography appeared.The quantum theory section introduces the basic assumptions and theories on which quantum cryptography is based,and undertakes subsequent agreements.The basic protocol part introduces the related parameters,definitions,and coding rates of known quantum key distribution protocols according to the development process of quantum key distribution and the progressive relationship of the protocol.Analyze the advantages and disadvantages of each protocol.In the third part,we discuss the practical QKD system,parameter fluctuation is inevitable due to imperfect equipment or external factors.Specifically,we can not prepare the quantum state perfectly as described in operator or keep emitting light pulses in a certain intensity.Fortunately,most of those defects that can give eavesdroppers the possibility to attack the system has been studied before.To regarding modulation preparation,Loss-tolerant was proposed to estimate the preparation defects.Also it has been proved that three-intensity decoy-state protocols with the HPCS is efficiently getting close to the ideal decoy-state method and robust enough against intensity fluctuations.In the last part,we proposed a four state RFI-QKD protocol with HPCS to increase both the key generation rates and the transmission distance.In addition,decoy state method is involved to eliminate PNS attack and finite key lengths is unavoidable in practical system.The performance of our scheme with source flaws and intensity fluctuations is analyzed and compared with the protocols with WCS through simulation.