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Dianzi xuebao

Decoy-State Quantum Key Distribution Based on State-Dependent Imperfections

Xiang-Qun Fu

Published Jan 1, 2012• 0 citations
OpenAlex

Abstract

This paper proposes models for analyzing the security of decoy-state quantum key distribution(QKD) with state-dependent imperfections.With the privacy amplification method of QKD's post-processing techniques,we introduce the decoy-state method used widely in QKD system to estimate the phase error rate more accurately than the case without decoy-state method.Based on this,we obtain the formula of secret key generation rates for decoy-state QKD with state-dependent imperfections,and characterize the relationship among key generation rates,state dependent parameter,detection efficiency and transmission distance.Numerical simulations indicate that the secure key generation rates' tolerance to state-dependent imperfections decreases with the growing distance,but increases with the improving detection efficiency,which,to some extent,show the validity of the formula we obtain.

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This paper proposes models for analyzing the security of decoy-state quantum key distribution(QKD) with state-dependent imperfections.With the privacy amplification method of QKD's post-processing techniques,we introduce the decoy-state method used widely in QKD system to estimate the phase error rate more accurately than the case without decoy-state method.Based on this,we obtain the formula of secret key generation rates for decoy-state QKD with state-dependent imperfections,and characterize the relationship among key generation rates,state dependent parameter,detection efficiency and transmission distance.Numerical simulations indicate that the secure key generation rates' tolerance to state-dependent imperfections decreases with the growing distance,but increases with the improving detection efficiency,which,to some extent,show the validity of the formula we obtain.
The use of decoy states in quantum key distribution (QKD) has provided a method for substantially increasing the secret key rate and distance that can be covered by QKD protocols with practical signals. The security analysis of these schemes, however, leaves open the possibility that the development of better proof techniques or better classical postprocessing methods might further improve their performance in realistic scenarios. In this paper, we derive upper bounds on the secure key rate for decoy-state QKD. These bounds are based basically only on the classical correlations established by the legitimate users during the quantum communication phase of the protocol. The only assumption about the possible postprocessing methods is that double click events are randomly assigned to single click events. Further, we consider only secure key rates based on the uncalibrated device scenario which assigns imperfections such as detection inefficiency to the eavesdropper. Our analysis relies on two preconditions for secure two-way and one-way QKD. The legitimate users need to prove that there exists no separable state (in the case of two-way QKD) or that there exists no quantum state having a symmetric extension (one-way QKD) that is compatible with the available measurements results. Both criteria have been previously applied to evaluate single-photon implementations of QKD. Here we use them to investigate a realistic source of weak coherent pulses. The resulting upper bounds can be formulated as a convex optimization problem known as a semidefinite program which can be efficiently solved. For the standard four-state QKD protocol, they are quite close to known lower bounds, thus showing that there are clear limits to the further improvement of classical postprocessing techniques in decoy-state QKD.
Abstract Passive generation is a sophisticated way of state preparation in quantum key distribution (QKD) systems which is designed to exploit some internal physical process as a source of randomness. It can be profitable in a wide range of scenarios. However, the original analysis of the passive scheme implies an ideal interference which is almost impossible to assure in practice, therefore utilizing such method potentially compromises the security of the system. Here we develop a general technique to estimate decoy-state parameters for a passive protocol with an arbitrary experimental distribution of intensity. We compare this analysis with the original method and show that the proposed technique can provide higher key generation rates.
To increase the security distance of quantum communication,a new scheme of decoy state quantum key distribution with a modified coherent state is proposed.The probability of multi-photon pulse in weak coherent source can be decreased by canceling two photon pulses to improve the security distance.Based on the math model of the decoy state QKD,the formula for the yield and error rate of the single photon pulse with the Modified Coherent State is deduced,and substituted in GLLP to calculate the generation rate of quantum keys.Results show that the decoy state with the Modified Coherent State can increase the secure communication distance about 10%,which is very close to that of the perfect decoy state QKD.
Quantum key generation rate of decoy state quantum key distribution(QKD) with a heralded single-photon source(HSPS) is deduced.Relationship between quantum key generation rate and detection efficiency of sender is discussed.Optimal intensities and key generation rate of decoy state QKD with a weak coherent pulse(WCP) and an HSPS are analyzed.It shows that key generation rate increases with increase of detection efficiency of sender and its security distance is the same as with a perfect single photon source.Decoy state QKD increases security distance and key rate of QKD.Due to less dark counts QKD with HSPS works longer distance than WCP.
Quantum key distribution (QKD) offers an approach for secure communication over quantum channels, based on the principles of quantum mechanics. However, the inevitable imperfections in QKD systems can introduce critical vulnerabilities, posing significant challenges to the deployment of QKD in terms of both practical security and performance. In this work, we present a comprehensive security analysis of QKD in the practical scenarios involving imperfections in modulation spaces. Specifically, our analysis focuses on the imperfections related to encoding, intensity modulation, and their characterization. We provide a unified framework based on the operator dominance method to overcome these issues and achieve a tight estimation of the secret key rate (SKR). The simulation results show that the SKR in practical scenarios, with parameters characterized from commercial QKD systems, closely matches the SKR under ideal conditions. In the finite case, the maximum transmission distance can reach up to 250 km with total pulse number N=1012N=10^{12}N=1012 and the SKR closely approaches the asymptotic limit up to 250 km with N=1014N=10^{14}N=1014. This validates the robustness of our method against imperfections in state preparation and characterization. Furthermore, the feasibility and robustness of method in measurement-device-independent (MDI) QKD have also been demonstrated. Our analysis not only promotes advancements in enhancing practical security and performance but also highlights the feasibility of deploying QKD for actual applications.
In practical quantum key distribution system, the state preparation and measurement have state-dependent imperfections comparing with the ideal BB84 protocol. If the state-dependent imperfection can not be regarded as an unitary transformation, it should not be considered as part of quantum channel noise introduced by the eavesdropper, the commonly used secret key rate formula GLLP can not be applied correspondingly. In this paper, the unconditional security of quantum key distribution with state-dependent imperfections will be analyzed by estimating upper bound of the phase error rate in the quantum channel and the imperfect measurement. Interestingly, since Eve can not control all phase error in the quantum key distribution system, the final secret key rate under constant quantum bit error rate can be improved comparing with the perfect quantum key distribution protocol.