Quantum key distribution(QKD)is a technology that can resist the threat of quantum computers to existing conventional cryptographic protocols.However,due to the stringent requirements of the quantum key generation env...Quantum key distribution(QKD)is a technology that can resist the threat of quantum computers to existing conventional cryptographic protocols.However,due to the stringent requirements of the quantum key generation environment,the generated quantum keys are considered valuable,and the slow key generation rate conflicts with the high-speed data transmission in traditional optical networks.In this paper,for the QKD network with a trusted relay,which is mainly based on point-to-point quantum keys and has complex changes in network resources,we aim to allocate resources reasonably for data packet distribution.Firstly,we formulate a linear programming constraint model for the key resource allocation(KRA)problem based on the time-slot scheduling.Secondly,we propose a new scheduling scheme based on the graded key security requirements(GKSR)and a new micro-log key storage algorithm for effective storage and management of key resources.Finally,we propose a key resource consumption(KRC)routing optimization algorithm to properly allocate time slots,routes,and key resources.Simulation results show that the proposed scheme significantly improves the key distribution success rate and key resource utilization rate,among others.展开更多
Quantum key distribution(QKD),rooted in quantum mechanics,offers information-theoretic security.However,practi-cal systems open security threats due to imperfections,notably bright-light blinding attacks targeting sin...Quantum key distribution(QKD),rooted in quantum mechanics,offers information-theoretic security.However,practi-cal systems open security threats due to imperfections,notably bright-light blinding attacks targeting single-photon detectors.Here,we propose a concise,robust defense strategy for protecting single-photon detectors in QKD systems against blinding attacks.Our strategy uses a dual approach:detecting the bias current of the avalanche photodiode(APD)to defend against con-tinuous-wave blinding attacks,and monitoring the avalanche amplitude to protect against pulsed blinding attacks.By integrat-ing these two branches,the proposed solution effectively identifies and mitigates a wide range of bright light injection attempts,significantly enhancing the resilience of QKD systems against various bright-light blinding attacks.This method forti-fies the safeguards of quantum communications and offers a crucial contribution to the field of quantum information security.展开更多
Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devi...Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devices.To alleviate the influence of misalignments,a method exploiting statistics from mismatched basis is proposed to enable uncharacterized sources to generate secure keys in QKD.In this work,we propose a scheme on four-intensity decoy-state quantum key distribution with uncharacterized heralded single-photon sources.It only requires the source states are prepared in a two-dimensional Hilbert space,and can thus reduce the complexity of practical realizations.Moreover,we carry out corresponding numerical simulations and demonstrate that our present four-intensity decoy-state scheme can achieve a much higher key rate compared than a three-intensity decoy-state method,and meantime it can obtain a longer transmission distance compared than the one using weak coherent sources.展开更多
Quantum key distribution(QKD) generates information-theoretical secure keys between two parties based on the physical laws of quantum mechanics. The phase-matching(PM) QKD protocol allows the key rate to break the qua...Quantum key distribution(QKD) generates information-theoretical secure keys between two parties based on the physical laws of quantum mechanics. The phase-matching(PM) QKD protocol allows the key rate to break the quantum channel secret key capacity limit without quantum repeaters, and the security of the protocol is demonstrated by using equivalent entanglement. In this paper, the wavelength division multiplexing(WDM) technique is applied to the PM-QKD protocol considering the effect of crosstalk noise on the secret key rate. The performance of PM-QKD protocol based on WDM with the influence of adjacent classical channels and Raman scattering is analyzed by numerical simulations to maximize the total secret key rate of the QKD, providing a reference for future implementations of QKD based on WDM techniques.展开更多
Quantum key distribution(QKD)is a sophisticated method for securing information by leveraging the principles of quantum mechanics.Its objective is to establish a confidential key between authorized partners who are co...Quantum key distribution(QKD)is a sophisticated method for securing information by leveraging the principles of quantum mechanics.Its objective is to establish a confidential key between authorized partners who are connected via both a quantum channel and a classical authentication channel.This paper presents a comprehensive overview of QKD protocols,chip-based QKD systems,quantum light sources,quantum detectors,fiber-based QKD networks,space-based QKD systems,as well as the applications and prospects of QKD technology.展开更多
Quantum key distribution(QKD)in principle can provide unconditional secure communication between distant parts.However,when finite-key length is taken into account,the security can only be ensured within certain secur...Quantum key distribution(QKD)in principle can provide unconditional secure communication between distant parts.However,when finite-key length is taken into account,the security can only be ensured within certain security level.In this paper,we adopt the Chernoff bound analysis method to deal with finite-key-size effects,carrying out corresponding investigations on the relationship between the key generation rate and security parameters for different protocols,including BB84,measurement-device-independent and twin-field QKD protocols.Simulation results show that there exists a fundamental limit between the key rate and the security parameters.Therefore,this study can provide valuable references for practical application of QKD,getting a nice balance between the key generation rate and the security level.展开更多
The huge discrepancies between actual devices and theoretical assumptions severely threaten the security of quantum key distribution.Recently,a general new framework called the reference technique has attracted wide a...The huge discrepancies between actual devices and theoretical assumptions severely threaten the security of quantum key distribution.Recently,a general new framework called the reference technique has attracted wide attention in defending against the imperfect sources of quantum key distribution.Here,the state preparation flaws,the side channels of mode dependencies,the Trojan horse attacks,and the pulse classical correlations are studied by using the reference technique on the phase-matching protocol.Our simulation results highlight the importance of the actual secure parameters choice for transmitters,which is necessary to achieve secure communication.Increasing the single actual secure parameter will reduce the secure key rate.However,as long as the parameters are set properly,the secure key rate is still high.Considering the influences of multiple actual secure parameters will significantly reduce the secure key rate.These actual secure parameters must be considered when scientists calibrate transmitters.This work is an important step towards the practical and secure implementation of phase-matching protocol.In the future,it is essential to study the main parameters,find out their maximum and general values,classify the multiple parameters as the same parameter,and give countermeasures.展开更多
Quantum key distribution(QKD)system based on passive silica planar lightwave circuit(PLC)asymmetric Mach–Zehnder interferometers(AMZI)is characterized with thermal stability,low loss and sufficient integration scalab...Quantum key distribution(QKD)system based on passive silica planar lightwave circuit(PLC)asymmetric Mach–Zehnder interferometers(AMZI)is characterized with thermal stability,low loss and sufficient integration scalability.However,waveguide stresses,both intrinsic and temperature-induced stresses,have significant impacts on the stable operation of the system.We have designed silica AMZI chips of 400 ps delay,with bend waveguides length equalized for both long and short arms to balance the stresses thereof.The temperature characteristics of the silica PLC AMZI chip are studied.The interference visibility at the single photon level is kept higher than 95%over a wide temperature range of 12℃.The delay time change is 0.321 ps within a temperature change of 40℃.The spectral shift is 0.0011 nm/0.1℃.Temperature-induced delay time and peak wavelength variations do not affect the interference visibility.The experiment results demonstrate the advantage of being tolerant to chip temperature fluctuations.展开更多
Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution,breaking through the traditional linear key-rate bound.In practical applications,finite data size can cause significant...Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution,breaking through the traditional linear key-rate bound.In practical applications,finite data size can cause significant system performance to deteriorate when data size is below 1010.In this work,an improved statistical fluctuation analysis method is applied for the first time to two decoy-states phase-matching quantum key distribution,offering a new insight and potential solutions for improving the key generation rate and the maximum transmission distance while maintaining security.Moreover,we also compare the influence of the proposed improved statistical fluctuation analysis method on system performance with those of the Gaussian approximation and Chernoff-Hoeffding boundary methods on system performance.The simulation results show that the proposed scheme significantly improves the key generation rate and maximum transmission distance in comparison with the Chernoff-Hoeffding approach,and approach the results obtained when the Gaussian approximation is employed.At the same time,the proposed scheme retains the same security level as the Chernoff-Hoeffding method,and is even more secure than the Gaussian approximation.展开更多
Quantum key distribution provides an unconditional secure key sharing method in theory,but the imperfect factors of practical devices will bring security vulnerabilities.In this paper,we characterize the imperfections...Quantum key distribution provides an unconditional secure key sharing method in theory,but the imperfect factors of practical devices will bring security vulnerabilities.In this paper,we characterize the imperfections of the sender and analyze the possible attack strategies of Eve.Firstly,we present a quantized model for distinguishability of decoy states caused by intensity modulation.Besides,considering that Eve may control the preparation of states through hidden variables,we evaluate the security of preparation in practical quantum key distribution(QKD)scheme based on the weak-randomness model.Finally,we analyze the influence of the distinguishability of decoy state to secure key rate,for Eve may conduct the beam splitting attack and control the channel attenuation of different parts.Through the simulation,it can be seen that the secure key rate is sensitive to the distinguishability of decoy state and weak randomness,especially when Eve can control the channel attenuation.展开更多
In a practical quantum key distribution(QKD) system, imperfect equipment, especially the single-photon detector,can be eavesdropped on by a blinding attack. However, the original blinding attack may be discovered by...In a practical quantum key distribution(QKD) system, imperfect equipment, especially the single-photon detector,can be eavesdropped on by a blinding attack. However, the original blinding attack may be discovered by directly detecting the current. In this paper, we propose a probabilistic blinding attack model, where Eve probabilistically applies a blinding attack without being caught by using only an existing intuitive countermeasure. More precisely, our countermeasure solves the problem of how to define the bound in the limitation of precision of current detection, and then we prove security of the practical system by considering the current parameter. Meanwhile, we discuss the bound of the quantum bit error rate(QBER) introduced by Eve, by which Eve can acquire information without the countermeasure.展开更多
High-dimensional quantum states key distribution(HD-QKD) can enable more than one bit per photon and tolerate more noise. Recently, a practical HD-QKD system based on time-phase states has provided a secret key at Mbp...High-dimensional quantum states key distribution(HD-QKD) can enable more than one bit per photon and tolerate more noise. Recently, a practical HD-QKD system based on time-phase states has provided a secret key at Mbps over metropolitan distances. For the purposes of further improving the secret key rate of a practical HD-QKD system, we make two main contributions in this work. Firstly, we present an improved parameter estimation for this system in the finite-key scenario based on the Chernoff bound and the improved Chernoff bound. Secondly, we analyze how the dimension d affects the performance of the practical HD-QKD system.We present numerical simulations about the secret key rate of the practical HD-QKD system based on different parameter estimation methods. It is found that using the improved Chernoff bound can improve the secret key rate and maximum channel loss of the practical HD-QKD system. In addition, a mixture of the 4-level and 8-level practical HD-QKD system can provide better performance in terms of the key generation rate over metropolitan distances.展开更多
The unconditional security of quantum key distribution(QKD) can be guaranteed by the nature of quantum physics.Compared with the traditional two-dimensional BB84 QKD protocol, high-dimensional quantum key distribution...The unconditional security of quantum key distribution(QKD) can be guaranteed by the nature of quantum physics.Compared with the traditional two-dimensional BB84 QKD protocol, high-dimensional quantum key distribution(HDQKD) can be applied to generate much more secret key.Nonetheless, practical imperfections in realistic systems can be exploited by the third party to eavesdrop the secret key.The practical beam splitter has a correlation with wavelength,where different wavelengths have different coupling ratios.Using this property, we propose a wavelength-dependent attack towards time-bin high-dimensional QKD system.What is more, we demonstrate that this attacking protocol can be applied to arbitrary d-dimensional QKD system, and higher-dimensional QKD system is more vulnerable to this attacking strategy.展开更多
We propose a new scheme to enhance the performance of the Gussian-modulated coherent-state continuous-variable measurement-device-independent quantum key distribution(CV-MDI-QKD)system via quantum scissors(QS)operatio...We propose a new scheme to enhance the performance of the Gussian-modulated coherent-state continuous-variable measurement-device-independent quantum key distribution(CV-MDI-QKD)system via quantum scissors(QS)operation at Bob's side.As an non-deterministic amplifying setup,we firstly introduce the QS-enhanced CV-MDI-QKD protocol and then investigate the success probability of the QS operation in accordance with the equivalent one-way scheme.Afterwards,we investigate the effect of the QS operation on the proposed scheme and analyze the performance of the QS-enhanced CV-MDI-QKD system under the extreme asymmetric circumstance.Simulation results show that the QS operation can indeed improve the performance of the CV-MDI-QKD system considerably.QS-enhanced CV-MDI-QKD protocol outperforms the original CV-MDI-QKD protocol in both the maximum transmission distance and the secret key rate.Moreover,the better the performance of QS operation,the more significant the improvement of performance of the system.展开更多
Continuous-variable quantum key distribution(CVQKD)allows legitimate parties to extract and exchange secret keys.However,the tradeoff between the secret key rate and the accuracy of parameter estimation still around t...Continuous-variable quantum key distribution(CVQKD)allows legitimate parties to extract and exchange secret keys.However,the tradeoff between the secret key rate and the accuracy of parameter estimation still around the present CVQKD system.In this paper,we suggest an approach for parameter estimation of the CVQKD system via artificial neural networks(ANN),which can be merged in post-processing with less additional devices.The ANN-based training scheme,enables key prediction without exposing any raw key.Experimental results show that the error between the predicted values and the true ones is in a reasonable range.The CVQKD system can be improved in terms of the secret key rate and the parameter estimation,which involves less additional devices than the traditional CVQKD system.展开更多
In a quantum key distribution system, it is crucial to keep the extinction ratio of the coherent pulses stable. This means that the direct current bias point of the electro-optic modulator (EOM) used for generating ...In a quantum key distribution system, it is crucial to keep the extinction ratio of the coherent pulses stable. This means that the direct current bias point of the electro-optic modulator (EOM) used for generating coherent pulses must be locked. In this paper, an autobias control system based on a lock-in-amplifier for the EOM is introduced. Its drift information extracting theory and control method are analyzed comprehensively. The long term drift of the extinction ratio of the coherent pulses is measured by a single photon detector, which indicates that the autobias control system is effective for stabilizing the bias point of the EOM.展开更多
Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in ...Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in the quantum key distribution system is analysed to propose a new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology to reduce quantum bits error rates under some transmission rate conditions, The proposed synchronization scheme can not only completely eliminate noise photons from the bright background light of the the clock signal, but also suppress the fibre nonlinear crosstalk.展开更多
The most severe problem of a two-way "plug-and-play" (p &: p) quantum key distribution system is that the source can be controlled by the eavesdropper. This kind of source is defined as an "untrusted source". ...The most severe problem of a two-way "plug-and-play" (p &: p) quantum key distribution system is that the source can be controlled by the eavesdropper. This kind of source is defined as an "untrusted source". This paper discusses the effects of the fluctuation of internal transmittance on the final key generation rate and the transmission distance. The security of the standard BB84 protocol, one-decoy state protocol, and weak+vacuum decoy state protocol, with untrusted sources and the fluctuation of internal transmittance are studied. It is shown that the one-decoy state is sensitive to the statistical fluctuation but weak+vacuum decoy state is only slightly affected by the fluctuation. It is also shown that both the maximum secure transmission distance and final key generation rate are reduced when Alice's laboratory transmittance fluctuation is considered.展开更多
Post-processing is indispensable in quantum key distribution (QKD), which is aimed at sharing secret keys between two distant parties. It mainly consists of key reconciliation and privacy amplification, which is use...Post-processing is indispensable in quantum key distribution (QKD), which is aimed at sharing secret keys between two distant parties. It mainly consists of key reconciliation and privacy amplification, which is used for sharing the same keys and for distilling unconditional secret keys. In this paper, we focus on speeding up the privacy amplification process by choosing a simple multiplicative universal class of hash functions. By constructing an optimal multiplication algorithm based on four basic multiplication algorithms, we give a fast software implementation of length-adaptive privacy amplification. "Length-adaptive" indicates that the implementation of privacy amplification automatically adapts to different lengths of input blocks. When the lengths of the input blocks are 1 Mbit and 10 Mbit, the speed of privacy amplification can be as fast as 14.86 Mbps and 10.88 Mbps, respectively. Thus, it is practical for GHz or even higher repetition frequency QKD systems.展开更多
In a quantum key distribution(QKD) system, the error rate needs to be estimated for determining the joint probability distribution between legitimate parties, and for improving the performance of key reconciliation....In a quantum key distribution(QKD) system, the error rate needs to be estimated for determining the joint probability distribution between legitimate parties, and for improving the performance of key reconciliation. We propose an efficient error estimation scheme for QKD, which is called parity comparison method(PCM). In the proposed method, the parity of a group of sifted keys is practically analysed to estimate the quantum bit error rate instead of using the traditional key sampling. From the simulation results, the proposed method evidently improves the accuracy and decreases revealed information in most realistic application situations.展开更多
基金Project supported by the Natural Science Foundation of Jilin Province of China(Grant No.20210101417JC).
文摘Quantum key distribution(QKD)is a technology that can resist the threat of quantum computers to existing conventional cryptographic protocols.However,due to the stringent requirements of the quantum key generation environment,the generated quantum keys are considered valuable,and the slow key generation rate conflicts with the high-speed data transmission in traditional optical networks.In this paper,for the QKD network with a trusted relay,which is mainly based on point-to-point quantum keys and has complex changes in network resources,we aim to allocate resources reasonably for data packet distribution.Firstly,we formulate a linear programming constraint model for the key resource allocation(KRA)problem based on the time-slot scheduling.Secondly,we propose a new scheduling scheme based on the graded key security requirements(GKSR)and a new micro-log key storage algorithm for effective storage and management of key resources.Finally,we propose a key resource consumption(KRC)routing optimization algorithm to properly allocate time slots,routes,and key resources.Simulation results show that the proposed scheme significantly improves the key distribution success rate and key resource utilization rate,among others.
基金This work was supported by the Major Scientific and Technological Special Project of Anhui Province(202103a13010004)the Major Scientific and Technological Special Project of Hefei City(2021DX007)+1 种基金the Key R&D Plan of Shandong Province(2020CXGC010105)the China Postdoctoral Science Foundation(2021M700315).
文摘Quantum key distribution(QKD),rooted in quantum mechanics,offers information-theoretic security.However,practi-cal systems open security threats due to imperfections,notably bright-light blinding attacks targeting single-photon detectors.Here,we propose a concise,robust defense strategy for protecting single-photon detectors in QKD systems against blinding attacks.Our strategy uses a dual approach:detecting the bias current of the avalanche photodiode(APD)to defend against con-tinuous-wave blinding attacks,and monitoring the avalanche amplitude to protect against pulsed blinding attacks.By integrat-ing these two branches,the proposed solution effectively identifies and mitigates a wide range of bright light injection attempts,significantly enhancing the resilience of QKD systems against various bright-light blinding attacks.This method forti-fies the safeguards of quantum communications and offers a crucial contribution to the field of quantum information security.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074194,12104240,and 62101285)the Industrial Prospect and Key Core Technology Projects of Jiangsu Provincial Key Research and Development Program(Grant No.BE2022071)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20192001 and BK20210582).
文摘Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devices.To alleviate the influence of misalignments,a method exploiting statistics from mismatched basis is proposed to enable uncharacterized sources to generate secure keys in QKD.In this work,we propose a scheme on four-intensity decoy-state quantum key distribution with uncharacterized heralded single-photon sources.It only requires the source states are prepared in a two-dimensional Hilbert space,and can thus reduce the complexity of practical realizations.Moreover,we carry out corresponding numerical simulations and demonstrate that our present four-intensity decoy-state scheme can achieve a much higher key rate compared than a three-intensity decoy-state method,and meantime it can obtain a longer transmission distance compared than the one using weak coherent sources.
基金supported by the State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications) (Grant No. IPOC2021ZT10)the National Natural Science Foundation of China (Grant No. 11904333)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. 2019XDA02)BUPT Innovation and Entrepreneurship Support Program (Grant No. 2022-YC-T051)。
文摘Quantum key distribution(QKD) generates information-theoretical secure keys between two parties based on the physical laws of quantum mechanics. The phase-matching(PM) QKD protocol allows the key rate to break the quantum channel secret key capacity limit without quantum repeaters, and the security of the protocol is demonstrated by using equivalent entanglement. In this paper, the wavelength division multiplexing(WDM) technique is applied to the PM-QKD protocol considering the effect of crosstalk noise on the secret key rate. The performance of PM-QKD protocol based on WDM with the influence of adjacent classical channels and Raman scattering is analyzed by numerical simulations to maximize the total secret key rate of the QKD, providing a reference for future implementations of QKD based on WDM techniques.
基金Project supported by the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0300701)the National Key Research and Development Program of China (Grant No.2018YFA0306403)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No.XDB43000000)。
文摘Quantum key distribution(QKD)is a sophisticated method for securing information by leveraging the principles of quantum mechanics.Its objective is to establish a confidential key between authorized partners who are connected via both a quantum channel and a classical authentication channel.This paper presents a comprehensive overview of QKD protocols,chip-based QKD systems,quantum light sources,quantum detectors,fiber-based QKD networks,space-based QKD systems,as well as the applications and prospects of QKD technology.
基金the Research on Key Technology and Equipment Development of Autonomous and Controllable Lightweight Endogenous Safety of Power Monitoring System(Grant No.5108-202118056A-0-0-00).
文摘Quantum key distribution(QKD)in principle can provide unconditional secure communication between distant parts.However,when finite-key length is taken into account,the security can only be ensured within certain security level.In this paper,we adopt the Chernoff bound analysis method to deal with finite-key-size effects,carrying out corresponding investigations on the relationship between the key generation rate and security parameters for different protocols,including BB84,measurement-device-independent and twin-field QKD protocols.Simulation results show that there exists a fundamental limit between the key rate and the security parameters.Therefore,this study can provide valuable references for practical application of QKD,getting a nice balance between the key generation rate and the security level.
基金the National Key Research and Development Program of China(Grant Nos.2020YFA0309702 and 2020YFA0309701)the National Natural Science Foundation of China(Grant No.62101597)+2 种基金the China Postdoctoral Science Foundation(Grant No.2021M691536)the Natural Science Foundation of Henan(Grant Nos.202300410534 and 202300410532)the Anhui Initiative in Quantum Information Technologies。
文摘The huge discrepancies between actual devices and theoretical assumptions severely threaten the security of quantum key distribution.Recently,a general new framework called the reference technique has attracted wide attention in defending against the imperfect sources of quantum key distribution.Here,the state preparation flaws,the side channels of mode dependencies,the Trojan horse attacks,and the pulse classical correlations are studied by using the reference technique on the phase-matching protocol.Our simulation results highlight the importance of the actual secure parameters choice for transmitters,which is necessary to achieve secure communication.Increasing the single actual secure parameter will reduce the secure key rate.However,as long as the parameters are set properly,the secure key rate is still high.Considering the influences of multiple actual secure parameters will significantly reduce the secure key rate.These actual secure parameters must be considered when scientists calibrate transmitters.This work is an important step towards the practical and secure implementation of phase-matching protocol.In the future,it is essential to study the main parameters,find out their maximum and general values,classify the multiple parameters as the same parameter,and give countermeasures.
基金Project supported by the National Key R&D Program of China (Grant No.2018YFA0306403)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No.XDB43000000)+1 种基金Innovation Program for Quantum Science and TechnologyComputer Interconnect Technology Alliance Funding (Grant No.20220103)。
文摘Quantum key distribution(QKD)system based on passive silica planar lightwave circuit(PLC)asymmetric Mach–Zehnder interferometers(AMZI)is characterized with thermal stability,low loss and sufficient integration scalability.However,waveguide stresses,both intrinsic and temperature-induced stresses,have significant impacts on the stable operation of the system.We have designed silica AMZI chips of 400 ps delay,with bend waveguides length equalized for both long and short arms to balance the stresses thereof.The temperature characteristics of the silica PLC AMZI chip are studied.The interference visibility at the single photon level is kept higher than 95%over a wide temperature range of 12℃.The delay time change is 0.321 ps within a temperature change of 40℃.The spectral shift is 0.0011 nm/0.1℃.Temperature-induced delay time and peak wavelength variations do not affect the interference visibility.The experiment results demonstrate the advantage of being tolerant to chip temperature fluctuations.
文摘Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution,breaking through the traditional linear key-rate bound.In practical applications,finite data size can cause significant system performance to deteriorate when data size is below 1010.In this work,an improved statistical fluctuation analysis method is applied for the first time to two decoy-states phase-matching quantum key distribution,offering a new insight and potential solutions for improving the key generation rate and the maximum transmission distance while maintaining security.Moreover,we also compare the influence of the proposed improved statistical fluctuation analysis method on system performance with those of the Gaussian approximation and Chernoff-Hoeffding boundary methods on system performance.The simulation results show that the proposed scheme significantly improves the key generation rate and maximum transmission distance in comparison with the Chernoff-Hoeffding approach,and approach the results obtained when the Gaussian approximation is employed.At the same time,the proposed scheme retains the same security level as the Chernoff-Hoeffding method,and is even more secure than the Gaussian approximation.
基金the National Key Research and Development Program of China(Grant No.2020YFA0309702)NSAF(Grant No.U2130205)+3 种基金the National Natural Science Foundation of China(Grant Nos.62101597,61605248,and 61505261)the China Postdoctoral Science Foundation(Grant No.2021M691536)the Natural Science Foundation of Henan(Grant Nos.202300410534 and 202300410532)the Anhui Initiative in Quantum Information Technologies。
文摘Quantum key distribution provides an unconditional secure key sharing method in theory,but the imperfect factors of practical devices will bring security vulnerabilities.In this paper,we characterize the imperfections of the sender and analyze the possible attack strategies of Eve.Firstly,we present a quantized model for distinguishability of decoy states caused by intensity modulation.Besides,considering that Eve may control the preparation of states through hidden variables,we evaluate the security of preparation in practical quantum key distribution(QKD)scheme based on the weak-randomness model.Finally,we analyze the influence of the distinguishability of decoy state to secure key rate,for Eve may conduct the beam splitting attack and control the channel attenuation of different parts.Through the simulation,it can be seen that the secure key rate is sensitive to the distinguishability of decoy state and weak randomness,especially when Eve can control the channel attenuation.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CBA00200 and 2011CB921200)the National Natural Science Foundation of China(Grant Nos.61475148,61201239,61205118,and 11304397)the China Postdoctoral Science Foundation(Grant No.2013M540514)
文摘In a practical quantum key distribution(QKD) system, imperfect equipment, especially the single-photon detector,can be eavesdropped on by a blinding attack. However, the original blinding attack may be discovered by directly detecting the current. In this paper, we propose a probabilistic blinding attack model, where Eve probabilistically applies a blinding attack without being caught by using only an existing intuitive countermeasure. More precisely, our countermeasure solves the problem of how to define the bound in the limitation of precision of current detection, and then we prove security of the practical system by considering the current parameter. Meanwhile, we discuss the bound of the quantum bit error rate(QBER) introduced by Eve, by which Eve can acquire information without the countermeasure.
基金the National Basic Research Program of China under Grant No 2013CB338002the National Natural Science Foundation of China under Grant Nos 61505261,61675235,61605248 and 11304397
文摘High-dimensional quantum states key distribution(HD-QKD) can enable more than one bit per photon and tolerate more noise. Recently, a practical HD-QKD system based on time-phase states has provided a secret key at Mbps over metropolitan distances. For the purposes of further improving the secret key rate of a practical HD-QKD system, we make two main contributions in this work. Firstly, we present an improved parameter estimation for this system in the finite-key scenario based on the Chernoff bound and the improved Chernoff bound. Secondly, we analyze how the dimension d affects the performance of the practical HD-QKD system.We present numerical simulations about the secret key rate of the practical HD-QKD system based on different parameter estimation methods. It is found that using the improved Chernoff bound can improve the secret key rate and maximum channel loss of the practical HD-QKD system. In addition, a mixture of the 4-level and 8-level practical HD-QKD system can provide better performance in terms of the key generation rate over metropolitan distances.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0302600)the National Natural Science Foundation of China(Grant No.61675235)
文摘The unconditional security of quantum key distribution(QKD) can be guaranteed by the nature of quantum physics.Compared with the traditional two-dimensional BB84 QKD protocol, high-dimensional quantum key distribution(HDQKD) can be applied to generate much more secret key.Nonetheless, practical imperfections in realistic systems can be exploited by the third party to eavesdrop the secret key.The practical beam splitter has a correlation with wavelength,where different wavelengths have different coupling ratios.Using this property, we propose a wavelength-dependent attack towards time-bin high-dimensional QKD system.What is more, we demonstrate that this attacking protocol can be applied to arbitrary d-dimensional QKD system, and higher-dimensional QKD system is more vulnerable to this attacking strategy.
基金Project supported by the National Natural Science Foundation of China(Grant No.62001383)the Scientific Research Plan Project of Shaanxi Education Department(Natural Science Special Project)(Grant No.19JK0847).
文摘We propose a new scheme to enhance the performance of the Gussian-modulated coherent-state continuous-variable measurement-device-independent quantum key distribution(CV-MDI-QKD)system via quantum scissors(QS)operation at Bob's side.As an non-deterministic amplifying setup,we firstly introduce the QS-enhanced CV-MDI-QKD protocol and then investigate the success probability of the QS operation in accordance with the equivalent one-way scheme.Afterwards,we investigate the effect of the QS operation on the proposed scheme and analyze the performance of the QS-enhanced CV-MDI-QKD system under the extreme asymmetric circumstance.Simulation results show that the QS operation can indeed improve the performance of the CV-MDI-QKD system considerably.QS-enhanced CV-MDI-QKD protocol outperforms the original CV-MDI-QKD protocol in both the maximum transmission distance and the secret key rate.Moreover,the better the performance of QS operation,the more significant the improvement of performance of the system.
文摘Continuous-variable quantum key distribution(CVQKD)allows legitimate parties to extract and exchange secret keys.However,the tradeoff between the secret key rate and the accuracy of parameter estimation still around the present CVQKD system.In this paper,we suggest an approach for parameter estimation of the CVQKD system via artificial neural networks(ANN),which can be merged in post-processing with less additional devices.The ANN-based training scheme,enables key prediction without exposing any raw key.Experimental results show that the error between the predicted values and the true ones is in a reasonable range.The CVQKD system can be improved in terms of the secret key rate and the parameter estimation,which involves less additional devices than the traditional CVQKD system.
基金Project supported by the National Natural Science Foundation of China(Grant No.61108039)the Major Research Plan of the National Natural Science Foundation of China(Grant No.91121023)the Scientific Research Foundation of Graduate School of South China Normal University(Grant No.2012kyjj224)
文摘In a quantum key distribution system, it is crucial to keep the extinction ratio of the coherent pulses stable. This means that the direct current bias point of the electro-optic modulator (EOM) used for generating coherent pulses must be locked. In this paper, an autobias control system based on a lock-in-amplifier for the EOM is introduced. Its drift information extracting theory and control method are analyzed comprehensively. The long term drift of the extinction ratio of the coherent pulses is measured by a single photon detector, which indicates that the autobias control system is effective for stabilizing the bias point of the EOM.
基金Project supported by the Key Projects in the Guangzhou Science & Technology Pillar Program of China(Grant No.2008Z1-D501)the Guangdong Key Technologies Research & Development Program of China(Grant No.2007B010400009)+1 种基金the Guangdong Polytechnic Institute Scientific Research Fund,China(Grant No.0901)the Key Laboratory Program of Quantum Information of Chinese Academy of Sciences
文摘Three clock synchronization schemes for a quantum key distribution system are compared experimentally through the outdoor fibre and the interaction physical model of the the clock signal and the the quantum signal in the quantum key distribution system is analysed to propose a new synchronization scheme based on time division multiplexing and wavelength division multiplexing technology to reduce quantum bits error rates under some transmission rate conditions, The proposed synchronization scheme can not only completely eliminate noise photons from the bright background light of the the clock signal, but also suppress the fibre nonlinear crosstalk.
基金supported by the National Natural Science Foundation of China (Grant No. 11074072)
文摘The most severe problem of a two-way "plug-and-play" (p &: p) quantum key distribution system is that the source can be controlled by the eavesdropper. This kind of source is defined as an "untrusted source". This paper discusses the effects of the fluctuation of internal transmittance on the final key generation rate and the transmission distance. The security of the standard BB84 protocol, one-decoy state protocol, and weak+vacuum decoy state protocol, with untrusted sources and the fluctuation of internal transmittance are studied. It is shown that the one-decoy state is sensitive to the statistical fluctuation but weak+vacuum decoy state is only slightly affected by the fluctuation. It is also shown that both the maximum secure transmission distance and final key generation rate are reduced when Alice's laboratory transmittance fluctuation is considered.
基金supported by the National Basic Research Program of China(Grant Nos.2011CBA00200 and 2011CB921200)the National Natural Science Foundation of China(Grant Nos.60921091 and 61101137)
文摘Post-processing is indispensable in quantum key distribution (QKD), which is aimed at sharing secret keys between two distant parties. It mainly consists of key reconciliation and privacy amplification, which is used for sharing the same keys and for distilling unconditional secret keys. In this paper, we focus on speeding up the privacy amplification process by choosing a simple multiplicative universal class of hash functions. By constructing an optimal multiplication algorithm based on four basic multiplication algorithms, we give a fast software implementation of length-adaptive privacy amplification. "Length-adaptive" indicates that the implementation of privacy amplification automatically adapts to different lengths of input blocks. When the lengths of the input blocks are 1 Mbit and 10 Mbit, the speed of privacy amplification can be as fast as 14.86 Mbps and 10.88 Mbps, respectively. Thus, it is practical for GHz or even higher repetition frequency QKD systems.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CBA00200 and 2011CB921200)the National Natural Science Foundation of China(Grant Nos.61101137,61201239,and 61205118)
文摘In a quantum key distribution(QKD) system, the error rate needs to be estimated for determining the joint probability distribution between legitimate parties, and for improving the performance of key reconciliation. We propose an efficient error estimation scheme for QKD, which is called parity comparison method(PCM). In the proposed method, the parity of a group of sifted keys is practically analysed to estimate the quantum bit error rate instead of using the traditional key sampling. From the simulation results, the proposed method evidently improves the accuracy and decreases revealed information in most realistic application situations.