Information reconciliation is a significant step for a continuous-variable quantum key distribution（CV-QKD） system.We propose a reconciliation method that allows two authorized parties to extract a consistent and se...Information reconciliation is a significant step for a continuous-variable quantum key distribution（CV-QKD） system.We propose a reconciliation method that allows two authorized parties to extract a consistent and secure binary key in a CV-QKD protocol,which is based on Gaussian-modulated coherent states and homodyne detection.This method named spherical reconciliation is based on spherical quantization and non-binary low-density parity-check（LDPC） codes.With the suitable signal-to-noise ratio（SNR） and code rate of non-binary LDPC codes,spherical reconciliation algorithm has a high efficiency and can extend the transmission distance of CV-QKD.展开更多
Considering the ocean water＇s optical attenuation and the roughness of the sea surface, we analyze the security of continuous-variable （CV） quantum key distribution （QKD） based Mr-to-water channel. The effects of...Considering the ocean water＇s optical attenuation and the roughness of the sea surface, we analyze the security of continuous-variable （CV） quantum key distribution （QKD） based Mr-to-water channel. The effects of the absorp- tion and scattering on the transmittance of underwater quantum channel and the maximum secure transmission distance are studied. Considering the roughness of the sea surface, we simulate the performance bounds of CV QKD with different wind speeds using the Monte Carlo method. The results show that even if the secret key rate gradually reduces as the wind speed increases, the maximum transmission distance will not be affected obviously. Compared to the works regarding short-distance underwater optical communication, our research represents a significant step towards establishing secure communication between air platform and submarine vehicle.展开更多
Gaussian-modulated coherent state quantum key distribution is gradually moving towards practical application. Generally, the involved scheme is based on the binary random basis choice. To improve the performance and s...Gaussian-modulated coherent state quantum key distribution is gradually moving towards practical application. Generally, the involved scheme is based on the binary random basis choice. To improve the performance and security, we present a scheme based on a continuous random basis choice. The results show that our scheme obviously improves the performance, such as the secure communication distance. Our scheme avoids comparing the measurement basis and discarding the key bits, and it can be easily implemented with current technology. Moreover, the imperfection of the basis choice can be well removed by the known phase compensation algorithm.展开更多
The trans-media transmission of quantum pulse is one of means of free-space transmission which can be applied in continuous-variable quantum key distribution(CVQKD)system.In traditional implementations for atmospheric...The trans-media transmission of quantum pulse is one of means of free-space transmission which can be applied in continuous-variable quantum key distribution(CVQKD)system.In traditional implementations for atmospheric channels,the 1500-to-1600-nm pulse is regarded as an ideal quantum pulse carrier.However,the underwater transmission of this pulses tends to suffer from severe attenuation,which inevitably deteriorates the security of the whole CVQKD system.In this paper,we propose an alternative scheme for implementations of CVQKD over satellite-to-submarine channels.We estimate the parameters of the trans-media channels,involving atmosphere,sea surface and seawater and find that the shortwave infrared performs well in the above channels.The 450-nm pulse is used for generations of quantum signal carriers to accomplish quantum communications through atmosphere,sea surface and seawater channels.Numerical simulations show that the proposed scheme can achieve the transmission distance of 600 km.In addition,we demonstrate that non-Gaussian operations can further lengthen its maximal transmission distance,which contributes to the establishment of practical global quantum networks.展开更多
We propose a method to improve the secret key rate of an eight-state continuous-variable quantum key distribution（CVQKD） by using a linear optics cloning machine（LOCM）. In the proposed scheme, an LOCM is exploited...We propose a method to improve the secret key rate of an eight-state continuous-variable quantum key distribution（CVQKD） by using a linear optics cloning machine（LOCM）. In the proposed scheme, an LOCM is exploited to compensate for the imperfections of Bob＇s apparatus, so that the generated secret key rate of the eight-state protocol could be well enhanced. We investigate the security of our proposed protocol in a finite-size scenario so as to further approach the practical value of a secret key rate. Numeric simulation shows that the LOCM with reasonable tuning gain λ and transmittance τcan effectively improve the secret key rate of eight-state CVQKD in both an asymptotic limit and a finite-size regime.Furthermore, we obtain the tightest bound of the secure distance by taking the finite-size effect into account, which is more practical than that obtained in the asymptotic limit.展开更多
The well-known multi-dimensional reconciliation is an effective method used in the continuous-variable quantum key distribution in the long-distance and the low signal-to-noise-ratio scenarios.The virtual channel empl...The well-known multi-dimensional reconciliation is an effective method used in the continuous-variable quantum key distribution in the long-distance and the low signal-to-noise-ratio scenarios.The virtual channel employed to exchange data is generally established by using a finite-dimensional rotation in the reconciliation procedure.In this paper,we found that the finite dimension of the multi-dimensional reconciliation inevitably leads to the mismatch of the signal-to-noise-ratio between the quantum channel and the virtual channel,which may be called the finite-dimension effect.Such an effect results in an overestimation on the secret key rate,and subsequently induces vital practical security loopholes.展开更多
Continuous-variable quantum key distribution(CVQKD) protocols with entanglement in the middle(EM) enable long maximal transmission distances for quantum communications. For the security analysis of the protocols, it i...Continuous-variable quantum key distribution(CVQKD) protocols with entanglement in the middle(EM) enable long maximal transmission distances for quantum communications. For the security analysis of the protocols, it is usually assumed that Eve performs collective Gaussian attacks and there is a lack of finite-size analysis of the protocols. However,in this paper we consider the finite-size regime of the EM-based CVQKD protocols by exposing the protocol to collective attacks and coherent attacks. We differentiate between the collective attacks and the coherent attacks while comparing asymptotic key rate and the key rate in the finite-size scenarios. Moreover, both symmetric and asymmetric configurations are collated in a contrastive analysis. As expected, the derived results in the finite-size scenarios are less useful than those acquired in the asymptotic regime. Nevertheless, we find that CVQKD with entanglement in the middle is capable of providing fully secure secret keys taking the finite-size effects into account with transmission distances of more than 30 km.展开更多
Continuous-variable quantum key distribution (CVQKD) with the local local oscillator (LLO) is confronted with new security problems due to the reference pulses transmitted together with quantum signals over the insecu...Continuous-variable quantum key distribution (CVQKD) with the local local oscillator (LLO) is confronted with new security problems due to the reference pulses transmitted together with quantum signals over the insecure quantum channel. In this paper, we propose a method of phase attack on reference pulses of the LLO-CVQKD with time-multiplexing. Under this phase attack, the phase drifts of reference pulses are manipulated by eavesdroppers, and then the phase compensation error is increased. Consequently, the secret key rate is reduced due to the imperfect phase compensation for quantum signals. Based on the noise model of imperfect phase compensation, the practical security of LLO-CVQKD under phase attack is analyzed. The simulation results show that the practical security is reduced due to the phase attack, yet it is still tight when system parameters are estimated by training signals.展开更多
Compared with the fiber channel,the atmospheric channel offers the possibility of a broader geographical coverage and more flexible transmission for continuous-variable quantum key distribution(CVQKD).However,the fluc...Compared with the fiber channel,the atmospheric channel offers the possibility of a broader geographical coverage and more flexible transmission for continuous-variable quantum key distribution(CVQKD).However,the fluctuation of atmospheric conditions will lead to the loss of performance in atmospheric quantum communication.In this paper,we study how temperature affects atmospheric CVQKD.We mainly consider the temperature effects on the transmittance and interruption probability.From the numerical simulation analysis,it can be shown that the performance of atmospheric CVQKD is improved as temperature increases,with the other factors fixed.Moreover,the results in this work can be used to evaluate the feasibility of the experimental implementation of the atmospheric CVQKD protocols.展开更多
We present a Trojan-horse attack on the practical two-way continuous-variable quantum key distribution system. Our attack mainly focuses on the imperfection of the practical system that the modulator has a redundancy ...We present a Trojan-horse attack on the practical two-way continuous-variable quantum key distribution system. Our attack mainly focuses on the imperfection of the practical system that the modulator has a redundancy of modulation pulsewidth, which leaves a loophole for the eavesdropper inserting a Trojan-horse pulse. Utilizing the unique characteristics of two-way continuous-variable quantum key distribution that Alice only takes modulation operation on the received mode without any measurement, this attack allows the eavesdropper to render all of the final keys shared between the legitimate parties insecure without being detected. After analyzing the feasibility of the attack, the corresponding countermeasures are put forward.展开更多
A modified continuous-variable quantum key distribution （CVQKD） protocol is proposed by originating the entangled source from a malicious third party Eve in the middle instead of generating it from the trustworthy A...A modified continuous-variable quantum key distribution （CVQKD） protocol is proposed by originating the entangled source from a malicious third party Eve in the middle instead of generating it from the trustworthy Alice or Bob. This method is able to enhance the efficiency of the CVQKD scheme attacked by local oscillator （LO） intensity attack in terms of the generated secret key rate in quantum communication. The other indication of the improvement is that the maximum transmission distance and the maximum loss tolerance can be increased significantly, especially for CVQKD schemes based on homodyne detection.展开更多
When developing a practical continuous-variable quantum key distribution(CVQKD),the detector is necessary at the receiver's side.We investigate the practical security of the CVQKD system with an unbalanced heterod...When developing a practical continuous-variable quantum key distribution(CVQKD),the detector is necessary at the receiver's side.We investigate the practical security of the CVQKD system with an unbalanced heterodyne detector.The results show that unbalanced heterodyne detector introduces extra excess noise into the system and decreases the lower bound of the secret key rate without awareness of the legitimate communicators,which leaves loopholes for Eve to attack the system.In addition,we find that the secret key rate decreases more severely with the increase in the degree of imbalance and the excess noise induced by the imbalance is proportional to the intensity of the local oscillator(LO)under the same degree of imbalance.Finally,a countermeasure is proposed to resist these kinds of effects.展开更多
It is shown that the non-Gaussian operations can not only be used to prepare the nonclassical states, but also to improve the entanglement degree between Gaussian states. Thus these operations are naturally considered...It is shown that the non-Gaussian operations can not only be used to prepare the nonclassical states, but also to improve the entanglement degree between Gaussian states. Thus these operations are naturally considered to enhance the performance of continuous variable quantum key distribution(CVQKD), in which the non-Gaussian operations are usually placed on the right-side of the entangled source. Here we propose another scheme for further improving the performance of CVQKD with the entangled-based scheme by operating photon-addition operation on the left-side of the entangled source.It is found that the photon-addition operation on the left-side presents both higher success probability and better secure key rate and transmission distance than the photon subtraction on the right-side, although they share the same maximal tolerable noise. In addition, compared to both photon subtraction and photon addition on the right-side, our scheme shows the best performance and the photon addition on the right-side is the worst.展开更多
We show that the secret key generation rate can be balanced with the maximum secure distance of four-state continuous-variable quantum key distribution（CV-QKD） by using the linear optics cloning machine（LOCM）. Ben...We show that the secret key generation rate can be balanced with the maximum secure distance of four-state continuous-variable quantum key distribution（CV-QKD） by using the linear optics cloning machine（LOCM）. Benefiting from the LOCM operation, the LOCM-tuned noise can be employed by the reference partner of reconciliation to achieve higher secret key generation rates over a long distance. Simulation results show that the LOCM operation can flexibly regulate the secret key generation rate and the maximum secure distance and improve the performance of four-state CV-QKD protocol by dynamically tuning parameters in an appropriate range.展开更多
Continuous-variable quantum key distribution(CV QKD)using optical coherent detectors is practically favorable due to its low implementation cost,flexibility of wavelength division multiplexing,and compatibility with s...Continuous-variable quantum key distribution(CV QKD)using optical coherent detectors is practically favorable due to its low implementation cost,flexibility of wavelength division multiplexing,and compatibility with standard coherent communication technologies.However,the security analysis and parameter estimation of CV QKD are complicated due to the infinite-dimensional latent Hilbert space.Also,the transmission of strong reference pulses undermines the security and complicates the experiments.In this work,we tackle these two problems by presenting a time-bin-encoding CV protocol with a simple phase-error-based security analysis valid under general coherent attacks.With the key encoded into the relative intensity between two optical modes,the need for global references is removed.Furthermore,phase randomization can be introduced to decouple the security analysis of different photon-number components.We can hence tag the photon number for each round,effectively estimate the associated privacy using a carefully designed coherent-detection method,and independently extract encryption keys from each component.Simulations manifest that the protocol using multi-photon components increases the key rate by two orders of magnitude compared to the one using only the single-photon component.Meanwhile,the protocol with four-intensity decoy analysis is sufficient to yield tight parameter estimation with a short-distance key-rate performance comparable to the best Bennett-Brassard-1984 implementation.展开更多
Quantum key distribution(QKD)is a method for secure communication that utilizes quantum mechanics principles to distribute cryptographic keys between parties.Integrated photonics offer benefits such as compactness,sca...Quantum key distribution(QKD)is a method for secure communication that utilizes quantum mechanics principles to distribute cryptographic keys between parties.Integrated photonics offer benefits such as compactness,scalability,energy efficiency and the potential for extensive integration.We have achieved BB84 phase encoding and decoding,time-bin phase QKD,and the coherent one-way(COW)protocol on a planar lightwave circuit(PLC)platform.At the optimal temperature,our chip successfully prepared quantum states,performed decoding and calculated the secure key rate of the time-bin phasedecoding QKD to be 80.46 kbps over a 20 km transmission with a quantum bit error rate(QBER)of 4.23%.The secure key rate of the COW protocol was 18.18 kbps,with a phase error rate of 3.627%and a time error rate of 0.377%.The uniqueness of this technology lies in its combination of high integration and protocol flexibility,providing an innovative solution for the development of future quantum communication networks.展开更多
In the process of quantum key distribution(QKD), the communicating parties need to randomly determine quantum states and measurement bases. To ensure the security of key distribution, we aim to use true random sequenc...In the process of quantum key distribution(QKD), the communicating parties need to randomly determine quantum states and measurement bases. To ensure the security of key distribution, we aim to use true random sequences generated by true random number generators as the source of randomness. In practical systems, due to the difficulty of obtaining true random numbers, pseudo-random number generators are used instead. Although the random numbers generated by pseudorandom number generators are statistically random, meeting the requirements of uniform distribution and independence,they rely on an initial seed to generate corresponding pseudo-random sequences. Attackers may predict future elements from the initial elements of the random sequence, posing a security risk to quantum key distribution. This paper analyzes the problems existing in current pseudo-random number generators and proposes corresponding attack methods and applicable scenarios based on the vulnerabilities in the pseudo-random sequence generation process. Under certain conditions, it is possible to obtain the keys of the communicating parties with very low error rates, thus effectively attacking the quantum key system. This paper presents new requirements for the use of random numbers in quantum key systems, which can effectively guide the security evaluation of quantum key distribution protocols.展开更多
A mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states is proposed,named HPCS-PDS-MP-QKD protocol,where the light sources at Alice and Bob sides are changed to heralde...A mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states is proposed,named HPCS-PDS-MP-QKD protocol,where the light sources at Alice and Bob sides are changed to heralded pair-coherent sources,and devices designed to implement passive decoy states are included at the transmitter sides to generate the decoy state pulses in the decoy-state window passively.With the defined efficient events and the designed pairing strategy,the key bits and bases can be obtained by data post-processing.Numerical simulation results verify the feasibility of the proposed protocol.The results show that the proposed protocol can exceed PLOB when the pairing interval setting is greater than 10^(3),and the transmission distance exceeds 200 km.When the key transmission distance reaches 300 km and the maximum pairing interval is equivalent to 1,its performance is improved by nearly 1.8 times compared to the original MP-QKD protocol with a weak coherent source(WCS-MP-QKD),and by 6.8 times higher than that of WCS-MPQKD with passive decoy states(WCS-PDS-MP-QKD).Meanwhile,the key transmission distance can reach 480 km,and surpasses the WCS-PDS-MP-QKD protocol by nearly 40 km.When the total pulse length is greater than 10^(11),the key generation rate is almost equal to that of infinite pulses.It is a promising QKD protocol that breaks the PLOB bound without requiring phase tracking and locking,has a longer transmission distance and a higher key generation rate,and eliminates the potential of side channel attack.展开更多
The robustness of reference-frame-independent measurement-device-independent quantum key distribution(RFIMDI-QKD)against detection system vulnerabilities and its tolerance to reference frame drifts make it an ideal ch...The robustness of reference-frame-independent measurement-device-independent quantum key distribution(RFIMDI-QKD)against detection system vulnerabilities and its tolerance to reference frame drifts make it an ideal choice for hybrid channels.However,the impact of atmospheric turbulence on transmittance fluctuations remains a significant challenge for enhancing the performance of RFI-MDI-QKD.In this paper,we apply prefixed-threshold real-time selection and advantage distillation techniques to RFI-MDI-QKD in a hybrid channels scenario.Then,we analytically derive formulas for secret key rate in hybrid channels.Simulation results show that our modified scheme has apparent advances in both maximum tolerant loss and secure key rate compared to the fiber-only channel.Specifically,the result demonstrates that the maximum transmission distance can be improved by 15 km and 28 km when N=10^(12)and 10^(11).Our work not only provides a more robust key distribution protocol but also establishes a solid theoretical foundation for enhancing the performance of RFI-MDI-QKD in hybrid channels.展开更多
The advantage distillation(AD)technology has been proven to effectively improve the secret key rate and the communication distance of quantum key distribution(QKD).The mode-pairing quantum key distribution(MP-QKD)prot...The advantage distillation(AD)technology has been proven to effectively improve the secret key rate and the communication distance of quantum key distribution(QKD).The mode-pairing quantum key distribution(MP-QKD)protocol can overcome a fundamental physical limit,known as the Pirandola-Laurenza-Ottaviani-Banchi bound,without requiring global phase-locking.In this work,we propose a method based on multi-step AD to further enhance the performance of MP-QKD.The simulation results show that,compared to one-step AD,multi-step AD achieves better performance in long-distance scenarios and can tolerate a higher quantum bit error rate.Specifically,when the difference between the communication distances from Alice and Bob to Charlie is 25 km,50 km and 75 km,and the corresponding transmission distance exceeds 523 km,512 km and 496 km,respectively,the secret key rate achieved by multi-step AD surpasses that of one-step AD.Our findings indicate that the proposed method can effectively promote the application of MP-QKD in scenarios with high loss and high error rate.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1304613 and 11204379)
文摘Information reconciliation is a significant step for a continuous-variable quantum key distribution（CV-QKD） system.We propose a reconciliation method that allows two authorized parties to extract a consistent and secure binary key in a CV-QKD protocol,which is based on Gaussian-modulated coherent states and homodyne detection.This method named spherical reconciliation is based on spherical quantization and non-binary low-density parity-check（LDPC） codes.With the suitable signal-to-noise ratio（SNR） and code rate of non-binary LDPC codes,spherical reconciliation algorithm has a high efficiency and can extend the transmission distance of CV-QKD.
基金Supported by the National Natural Science Foundation of China under Grant No 61572529
文摘Considering the ocean water＇s optical attenuation and the roughness of the sea surface, we analyze the security of continuous-variable （CV） quantum key distribution （QKD） based Mr-to-water channel. The effects of the absorp- tion and scattering on the transmittance of underwater quantum channel and the maximum secure transmission distance are studied. Considering the roughness of the sea surface, we simulate the performance bounds of CV QKD with different wind speeds using the Monte Carlo method. The results show that even if the secret key rate gradually reduces as the wind speed increases, the maximum transmission distance will not be affected obviously. Compared to the works regarding short-distance underwater optical communication, our research represents a significant step towards establishing secure communication between air platform and submarine vehicle.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61332019,61671287,and 61631014)Northwest University Doctorate Dissertation of Excellence Funds,China(Grant No.YYB17022)the National Key Research and Development Program,China(Grant No.2016YFA0302600)
文摘Gaussian-modulated coherent state quantum key distribution is gradually moving towards practical application. Generally, the involved scheme is based on the binary random basis choice. To improve the performance and security, we present a scheme based on a continuous random basis choice. The results show that our scheme obviously improves the performance, such as the secure communication distance. Our scheme avoids comparing the measurement basis and discarding the key bits, and it can be easily implemented with current technology. Moreover, the imperfection of the basis choice can be well removed by the known phase compensation algorithm.
基金supported by the National Natural Science Foundation of China(Grant Nos.62101180 and 61871407)the Key R&D Program of Hunan Province(Grant No.2022GK2016)+1 种基金the State Key Laboratory of High Performance Computing,National University of Defense Technology(Grant No.202101-25)the Fundamental Research Funds for the Central Universities(Grant No.531118010371)。
文摘The trans-media transmission of quantum pulse is one of means of free-space transmission which can be applied in continuous-variable quantum key distribution(CVQKD)system.In traditional implementations for atmospheric channels,the 1500-to-1600-nm pulse is regarded as an ideal quantum pulse carrier.However,the underwater transmission of this pulses tends to suffer from severe attenuation,which inevitably deteriorates the security of the whole CVQKD system.In this paper,we propose an alternative scheme for implementations of CVQKD over satellite-to-submarine channels.We estimate the parameters of the trans-media channels,involving atmosphere,sea surface and seawater and find that the shortwave infrared performs well in the above channels.The 450-nm pulse is used for generations of quantum signal carriers to accomplish quantum communications through atmosphere,sea surface and seawater channels.Numerical simulations show that the proposed scheme can achieve the transmission distance of 600 km.In addition,we demonstrate that non-Gaussian operations can further lengthen its maximal transmission distance,which contributes to the establishment of practical global quantum networks.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61379153 and 61572529)
文摘We propose a method to improve the secret key rate of an eight-state continuous-variable quantum key distribution（CVQKD） by using a linear optics cloning machine（LOCM）. In the proposed scheme, an LOCM is exploited to compensate for the imperfections of Bob＇s apparatus, so that the generated secret key rate of the eight-state protocol could be well enhanced. We investigate the security of our proposed protocol in a finite-size scenario so as to further approach the practical value of a secret key rate. Numeric simulation shows that the LOCM with reasonable tuning gain λ and transmittance τcan effectively improve the secret key rate of eight-state CVQKD in both an asymptotic limit and a finite-size regime.Furthermore, we obtain the tightest bound of the secure distance by taking the finite-size effect into account, which is more practical than that obtained in the asymptotic limit.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61332019,61671287,and 61631014)the National Key Research and Development Program of China(Grant No.2016YFA0302600)
文摘The well-known multi-dimensional reconciliation is an effective method used in the continuous-variable quantum key distribution in the long-distance and the low signal-to-noise-ratio scenarios.The virtual channel employed to exchange data is generally established by using a finite-dimensional rotation in the reconciliation procedure.In this paper,we found that the finite dimension of the multi-dimensional reconciliation inevitably leads to the mismatch of the signal-to-noise-ratio between the quantum channel and the virtual channel,which may be called the finite-dimension effect.Such an effect results in an overestimation on the secret key rate,and subsequently induces vital practical security loopholes.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61572529,61871407,and 61801522)the China Postdoctoral Science Foundation(Grant Nos.2013M542119 and 2014T70772)
文摘Continuous-variable quantum key distribution(CVQKD) protocols with entanglement in the middle(EM) enable long maximal transmission distances for quantum communications. For the security analysis of the protocols, it is usually assumed that Eve performs collective Gaussian attacks and there is a lack of finite-size analysis of the protocols. However,in this paper we consider the finite-size regime of the EM-based CVQKD protocols by exposing the protocol to collective attacks and coherent attacks. We differentiate between the collective attacks and the coherent attacks while comparing asymptotic key rate and the key rate in the finite-size scenarios. Moreover, both symmetric and asymmetric configurations are collated in a contrastive analysis. As expected, the derived results in the finite-size scenarios are less useful than those acquired in the asymptotic regime. Nevertheless, we find that CVQKD with entanglement in the middle is capable of providing fully secure secret keys taking the finite-size effects into account with transmission distances of more than 30 km.
文摘Continuous-variable quantum key distribution (CVQKD) with the local local oscillator (LLO) is confronted with new security problems due to the reference pulses transmitted together with quantum signals over the insecure quantum channel. In this paper, we propose a method of phase attack on reference pulses of the LLO-CVQKD with time-multiplexing. Under this phase attack, the phase drifts of reference pulses are manipulated by eavesdroppers, and then the phase compensation error is increased. Consequently, the secret key rate is reduced due to the imperfect phase compensation for quantum signals. Based on the noise model of imperfect phase compensation, the practical security of LLO-CVQKD under phase attack is analyzed. The simulation results show that the practical security is reduced due to the phase attack, yet it is still tight when system parameters are estimated by training signals.
基金Project supported by the National Natural Science Foundation of China(Grant No.61505261)
文摘Compared with the fiber channel,the atmospheric channel offers the possibility of a broader geographical coverage and more flexible transmission for continuous-variable quantum key distribution(CVQKD).However,the fluctuation of atmospheric conditions will lead to the loss of performance in atmospheric quantum communication.In this paper,we study how temperature affects atmospheric CVQKD.We mainly consider the temperature effects on the transmittance and interruption probability.From the numerical simulation analysis,it can be shown that the performance of atmospheric CVQKD is improved as temperature increases,with the other factors fixed.Moreover,the results in this work can be used to evaluate the feasibility of the experimental implementation of the atmospheric CVQKD protocols.
基金supported by the National Basic Research Program of China(Grant No.2013CB338002)the National Natural Science Foundation of China(Grant Nos.11304397 and 61505261)
文摘We present a Trojan-horse attack on the practical two-way continuous-variable quantum key distribution system. Our attack mainly focuses on the imperfection of the practical system that the modulator has a redundancy of modulation pulsewidth, which leaves a loophole for the eavesdropper inserting a Trojan-horse pulse. Utilizing the unique characteristics of two-way continuous-variable quantum key distribution that Alice only takes modulation operation on the received mode without any measurement, this attack allows the eavesdropper to render all of the final keys shared between the legitimate parties insecure without being detected. After analyzing the feasibility of the attack, the corresponding countermeasures are put forward.
基金supported by the National Natural Science Foundation of China(Grant Nos.61379153,61401519,and 61572529)the Natural Science Foundation of Hunan Province,China(Grant No.2017JJ3415)+1 种基金the Science and Technology Project of Guangxi Zhuang Autonomous Region,China(Grant Nos.AC16380094and 1598008-29)the Natural Science Fund of Guangxi Zhuang Autonomous Region,China(Grant No.2015GXNSFAA139298)
文摘A modified continuous-variable quantum key distribution （CVQKD） protocol is proposed by originating the entangled source from a malicious third party Eve in the middle instead of generating it from the trustworthy Alice or Bob. This method is able to enhance the efficiency of the CVQKD scheme attacked by local oscillator （LO） intensity attack in terms of the generated secret key rate in quantum communication. The other indication of the improvement is that the maximum transmission distance and the maximum loss tolerance can be increased significantly, especially for CVQKD schemes based on homodyne detection.
基金the National Natural Science Foundation of China(Grant No.62001383)the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2019JM-591)。
文摘When developing a practical continuous-variable quantum key distribution(CVQKD),the detector is necessary at the receiver's side.We investigate the practical security of the CVQKD system with an unbalanced heterodyne detector.The results show that unbalanced heterodyne detector introduces extra excess noise into the system and decreases the lower bound of the secret key rate without awareness of the legitimate communicators,which leaves loopholes for Eve to attack the system.In addition,we find that the secret key rate decreases more severely with the increase in the degree of imbalance and the excess noise induced by the imbalance is proportional to the intensity of the local oscillator(LO)under the same degree of imbalance.Finally,a countermeasure is proposed to resist these kinds of effects.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11664017 and 11964013)the Training Program for Academic and Technical Leaders of Major Disciplines in Jiangxi Province,China (Grant No. 20204BCJL22053)。
文摘It is shown that the non-Gaussian operations can not only be used to prepare the nonclassical states, but also to improve the entanglement degree between Gaussian states. Thus these operations are naturally considered to enhance the performance of continuous variable quantum key distribution(CVQKD), in which the non-Gaussian operations are usually placed on the right-side of the entangled source. Here we propose another scheme for further improving the performance of CVQKD with the entangled-based scheme by operating photon-addition operation on the left-side of the entangled source.It is found that the photon-addition operation on the left-side presents both higher success probability and better secure key rate and transmission distance than the photon subtraction on the right-side, although they share the same maximal tolerable noise. In addition, compared to both photon subtraction and photon addition on the right-side, our scheme shows the best performance and the photon addition on the right-side is the worst.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61379153 and 61572529)
文摘We show that the secret key generation rate can be balanced with the maximum secure distance of four-state continuous-variable quantum key distribution（CV-QKD） by using the linear optics cloning machine（LOCM）. Benefiting from the LOCM operation, the LOCM-tuned noise can be employed by the reference partner of reconciliation to achieve higher secret key generation rates over a long distance. Simulation results show that the LOCM operation can flexibly regulate the secret key generation rate and the maximum secure distance and improve the performance of four-state CV-QKD protocol by dynamically tuning parameters in an appropriate range.
基金Engineering and Physical Sciences Research Council(project EP/T001011/1)Shenzhen-Hong Kong Cooperation Zone for Technology and Innovation(HZQB-KCZYB-2020050)+7 种基金Hong Kong Research Grant Council(R7035-21)Army Research Office(W911NF-23-1-0077)Multidisciplinary University Research Initiative(W911NF-21-1-0325)Air Force Office of Scientific Research(FA9550-19-1-0399,FA9550-21-1-0209)National Science Foundation(OMA-1936118,ERC-1941583,OMA-2137642)NTT ResearchDavid and Lucile Packard Foundation(2020-71479)Marshall and Arlene Bennett Family Research Program。
文摘Continuous-variable quantum key distribution(CV QKD)using optical coherent detectors is practically favorable due to its low implementation cost,flexibility of wavelength division multiplexing,and compatibility with standard coherent communication technologies.However,the security analysis and parameter estimation of CV QKD are complicated due to the infinite-dimensional latent Hilbert space.Also,the transmission of strong reference pulses undermines the security and complicates the experiments.In this work,we tackle these two problems by presenting a time-bin-encoding CV protocol with a simple phase-error-based security analysis valid under general coherent attacks.With the key encoded into the relative intensity between two optical modes,the need for global references is removed.Furthermore,phase randomization can be introduced to decouple the security analysis of different photon-number components.We can hence tag the photon number for each round,effectively estimate the associated privacy using a carefully designed coherent-detection method,and independently extract encryption keys from each component.Simulations manifest that the protocol using multi-photon components increases the key rate by two orders of magnitude compared to the one using only the single-photon component.Meanwhile,the protocol with four-intensity decoy analysis is sufficient to yield tight parameter estimation with a short-distance key-rate performance comparable to the best Bennett-Brassard-1984 implementation.
基金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 method for secure communication that utilizes quantum mechanics principles to distribute cryptographic keys between parties.Integrated photonics offer benefits such as compactness,scalability,energy efficiency and the potential for extensive integration.We have achieved BB84 phase encoding and decoding,time-bin phase QKD,and the coherent one-way(COW)protocol on a planar lightwave circuit(PLC)platform.At the optimal temperature,our chip successfully prepared quantum states,performed decoding and calculated the secure key rate of the time-bin phasedecoding QKD to be 80.46 kbps over a 20 km transmission with a quantum bit error rate(QBER)of 4.23%.The secure key rate of the COW protocol was 18.18 kbps,with a phase error rate of 3.627%and a time error rate of 0.377%.The uniqueness of this technology lies in its combination of high integration and protocol flexibility,providing an innovative solution for the development of future quantum communication networks.
文摘In the process of quantum key distribution(QKD), the communicating parties need to randomly determine quantum states and measurement bases. To ensure the security of key distribution, we aim to use true random sequences generated by true random number generators as the source of randomness. In practical systems, due to the difficulty of obtaining true random numbers, pseudo-random number generators are used instead. Although the random numbers generated by pseudorandom number generators are statistically random, meeting the requirements of uniform distribution and independence,they rely on an initial seed to generate corresponding pseudo-random sequences. Attackers may predict future elements from the initial elements of the random sequence, posing a security risk to quantum key distribution. This paper analyzes the problems existing in current pseudo-random number generators and proposes corresponding attack methods and applicable scenarios based on the vulnerabilities in the pseudo-random sequence generation process. Under certain conditions, it is possible to obtain the keys of the communicating parties with very low error rates, thus effectively attacking the quantum key system. This paper presents new requirements for the use of random numbers in quantum key systems, which can effectively guide the security evaluation of quantum key distribution protocols.
基金Project supported by the National Natural Science Foundation of China(Grant No.62375140)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX241191 and SJCX250315)the Open Research Fund of the National Laboratory of Solid State Microstructures(Grant No.M36055)。
文摘A mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states is proposed,named HPCS-PDS-MP-QKD protocol,where the light sources at Alice and Bob sides are changed to heralded pair-coherent sources,and devices designed to implement passive decoy states are included at the transmitter sides to generate the decoy state pulses in the decoy-state window passively.With the defined efficient events and the designed pairing strategy,the key bits and bases can be obtained by data post-processing.Numerical simulation results verify the feasibility of the proposed protocol.The results show that the proposed protocol can exceed PLOB when the pairing interval setting is greater than 10^(3),and the transmission distance exceeds 200 km.When the key transmission distance reaches 300 km and the maximum pairing interval is equivalent to 1,its performance is improved by nearly 1.8 times compared to the original MP-QKD protocol with a weak coherent source(WCS-MP-QKD),and by 6.8 times higher than that of WCS-MPQKD with passive decoy states(WCS-PDS-MP-QKD).Meanwhile,the key transmission distance can reach 480 km,and surpasses the WCS-PDS-MP-QKD protocol by nearly 40 km.When the total pulse length is greater than 10^(11),the key generation rate is almost equal to that of infinite pulses.It is a promising QKD protocol that breaks the PLOB bound without requiring phase tracking and locking,has a longer transmission distance and a higher key generation rate,and eliminates the potential of side channel attack.
基金supported by the National Natural Science Foundation of China(Grant Nos.61505261,62101597,61605248,and 61675235)the National Key Research and Development Program of China(Grant No.2020YFA0309702)the Natural Science Foundation of Henan Province(Grant Nos.202300410534 and 202300410534)。
文摘The robustness of reference-frame-independent measurement-device-independent quantum key distribution(RFIMDI-QKD)against detection system vulnerabilities and its tolerance to reference frame drifts make it an ideal choice for hybrid channels.However,the impact of atmospheric turbulence on transmittance fluctuations remains a significant challenge for enhancing the performance of RFI-MDI-QKD.In this paper,we apply prefixed-threshold real-time selection and advantage distillation techniques to RFI-MDI-QKD in a hybrid channels scenario.Then,we analytically derive formulas for secret key rate in hybrid channels.Simulation results show that our modified scheme has apparent advances in both maximum tolerant loss and secure key rate compared to the fiber-only channel.Specifically,the result demonstrates that the maximum transmission distance can be improved by 15 km and 28 km when N=10^(12)and 10^(11).Our work not only provides a more robust key distribution protocol but also establishes a solid theoretical foundation for enhancing the performance of RFI-MDI-QKD in hybrid channels.
基金supported by the National Natural Science Foundation of China(Grant Nos.62171144and 62031024)Guangxi Science Foundation(Grant Nos.2025GXNSFAA069137 and GXR-1BGQ2424005)Innovation Project of Guangxi Graduate Education(Grant No.YCBZ2025064)。
文摘The advantage distillation(AD)technology has been proven to effectively improve the secret key rate and the communication distance of quantum key distribution(QKD).The mode-pairing quantum key distribution(MP-QKD)protocol can overcome a fundamental physical limit,known as the Pirandola-Laurenza-Ottaviani-Banchi bound,without requiring global phase-locking.In this work,we propose a method based on multi-step AD to further enhance the performance of MP-QKD.The simulation results show that,compared to one-step AD,multi-step AD achieves better performance in long-distance scenarios and can tolerate a higher quantum bit error rate.Specifically,when the difference between the communication distances from Alice and Bob to Charlie is 25 km,50 km and 75 km,and the corresponding transmission distance exceeds 523 km,512 km and 496 km,respectively,the secret key rate achieved by multi-step AD surpasses that of one-step AD.Our findings indicate that the proposed method can effectively promote the application of MP-QKD in scenarios with high loss and high error rate.
