Security Analysis Of New Type Quantum Key Distribution Protocol

In modern science,information security plays a significant important role,such as personal privacy,financial security,national security,etc.With the rapid development of quantum computers and quantum algorithms,the existing classical cryptographic sys-tems based on the complexity of mathematical calculations have been greatly impacted.Therefore,how to deal with this challenge gave birth to quantum cryptography.The most important field in quantum cryptography is quantum key distribution.Quantum key distribution,based on the basic principles of quantum physics,such as the principle of non-cloning of unknown quantum states and the indivisibility of a sin-gle quantum state,can realize the process of sharing a string of almost identical secure keys for two distant parties.Combining with the "one-time pad" cryptography system,quantum key distribution is one of the way to realize unconditionally secure communi-cations,which vast majority of scholars believe.Since the first quantum key distribution protocol proposed in 1984,quantum key distribution has been greatly developed both theoretically and experimentally,and it is on the way to practical and even commercial implementation.Although quantum key distribution has been greatly developed in last three decades,new type quantum key distribution protocols are still emerging and each of them has its own advantages.For a new protocol,the most important thing is its se-curity analysis,which is the foundation for the practical application.For these newly proposed quantum key distribution protocol in the past decade,this thesis summarizes and develops some security analysis techniques,and consolidate the theoretical founda-tion of the quantum key distribution protocol.The main research results are summarized as follows:1.Due to the capability of tolerating high error rate and generating more key bits per trial,high-dimensional quantum key distribution attracts wide interest.Despite great progresses in high-dimensional quantum key distribution,there are still some gaps be-tween theory and experiment.One of these is that the security of secret key heavily de-pends on the number of the emitted signals.So far,the existing security proofs are only suitable in the case with infinite or unpractically large number of the emitted signals.Here,by introducing the idea of "key classification" and developing relevant techniques based on the uncertainty relation for smooth entropies,we propose a tight finite-key analysis suitable for generalized high-dimensional quantum key distribution protocols.Benefitting from our theory,high-dimensional quantum key distribution protocols with finite resources become experimentally feasible.2.Twin-field quantum key distribution(TF-QKD)and its variant protocols are highly attractive due to the advantage of overcoming the rate-loss limit for secret key rates of point-to-point QKD protocols.For variations of TF-QKD,the key point to ensure security is switching randomly between a code mode and a test mode.Among all TF-QKD protocols,their code modes are very different,e.g.modulating continuous phases,modulating only two opposite phases,and sending or not sending signal pulses.Here we show that,by discretizing the number of global phases in the code mode,we can give a unified view on the first two types of TF-QKD protocols,and demonstrate that increasing the number of discrete phases extends the achievable distance,and as a trade-off,lowers the secret key rate at short distances due to the phase post-selection.3.Combining the differential-quadrature-phase-shift(DQPS)quantum key dis-tribution(QKD)protocol and the recently proposed round-robin-differential-phase-shift(RRDPS),round-robin-differential-quadrature-phase-shift(RRDQPS)protocol has been proposed.However,a security proof of RRDQPS QKD protocol is still miss-ing and its advantage over the original RRDPS protocol is also unknown.Here,we give the security proof of RRDQPS protocol,by which we clearly show that RRDQPS protocol overwhlems the original RRDPS protocol in terms of tolerable error rate and secret key rate per pulse.More interestingly,our proof gives a unified theory covering the well known Bennet-Brassard 1984(BB84)protocol and RRDQPS protocol.Thus,it is confirmed that BB84 protocol is indeed a special case of RRDQPS protocol.4.In recent years,RRDPS QKD has attracted great attention for its unique char-acteristics,i.e.,the information leakage can be bounded without learning bit error rate.Though the RRDPS QKD has made a breakthrough,it is still a question of how RRDPS will perform with monitoring signal disturbance,e.g.,decoy-state and error rate statis-tics are both used.Here,we present simulations to study RRDPS protocol while mon-itoring signal disturbance.To our excitement,when using the infinite decoy-states method,RRDPS protocol can outperform the commonly used BB84 protocol in terms of channel length under typical experimental parameters.In the case of finite decoy states,we find that only two decoy-states and one signal state are sufficient to obtain performance very close to the infinite decoy-states case.