Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:quant-ph/0604094 · Physical Review A

Decoy-state quantum key distribution with two-way classical postprocessing

Xiongfeng Ma, Chi‐Hang Fred Fung, Frédéric Dupuis, Kai Chen, Kiyoshi Tamaki, Hoi‐Kwong Lo

Published Sep 25, 2006• 76 citations
arXivHTMLPDF

Abstract

Decoy states have recently been proposed as a useful method for substantially improving the performance of quantum key distribution (QKD) protocols when a coherent-state source is used. Previously, data postprocessing schemes based on one-way classical communications were considered for use with decoy states. In this paper, we develop two data postprocessing schemes for the decoy-state method using two-way classical communications. Our numerical simulation (using parameters from a specific QKD experiment as an example) results show that our scheme is able to extend the maximal secure distance from $142\phantom{\rule{0.3em}{0ex}}\mathrm{km}$ (using only one-way classical communications with decoy states) to $181\phantom{\rule{0.3em}{0ex}}\mathrm{km}$. The second scheme is able to achieve a 10% greater key generation rate in the whole regime of distances. We conclude that decoy-state QKD with two-way classical postprocessing is of practical interest.

DOI
10.1103/physreva.74.032330

Related papers

Upper bounds for the secure key rate of the decoy-state quantum key distribution

Marcos Curty, Tobias Moroder, Xiongfeng Ma +2 more

The use of decoy states in quantum key distribution (QKD) has provided a method for substantially increasing the secret key rate and distance that can be covered by QKD protocols with practical signals. The security analysis of these schemes, however, leaves open the possibility that the development of better proof techniques or better classical postprocessing methods might further improve their performance in realistic scenarios. In this paper, we derive upper bounds on the secure key rate for decoy-state QKD. These bounds are based basically only on the classical correlations established by the legitimate users during the quantum communication phase of the protocol. The only assumption about the possible postprocessing methods is that double click events are randomly assigned to single click events. Further, we consider only secure key rates based on the uncalibrated device scenario which assigns imperfections such as detection inefficiency to the eavesdropper. Our analysis relies on two preconditions for secure two-way and one-way QKD. The legitimate users need to prove that there exists no separable state (in the case of two-way QKD) or that there exists no quantum state having a symmetric extension (one-way QKD) that is compatible with the available measurements results. Both criteria have been previously applied to evaluate single-photon implementations of QKD. Here we use them to investigate a realistic source of weak coherent pulses. The resulting upper bounds can be formulated as a convex optimization problem known as a semidefinite program which can be efficiently solved. For the standard four-state QKD protocol, they are quite close to known lower bounds, thus showing that there are clear limits to the further improvement of classical postprocessing techniques in decoy-state QKD.

arXiv:0901.4669•Physical Review A•Mar 26, 2009•10 citations

Secure Communication with One Decoy State and Two Way Quantum Key Distribution Scheme

Mohd Fared Abdul Khir, Iskandar Bahari, M. N. Mohd Zain +1 more

Quantum Key Distribution (QKD) provides a mean for unconditionally secure secret key sharing for secure communication. For a practical QKD system, the recently proposed decoy state protocol has become an essential tool. In this work, we conduct numerical analysis against several bounds for one decoy state with two way QKD protocol and compare their performance in terms of key rate and maximum secure distance.

•Jan 1, 2013•1 citation

DECOY STATE QUANTUM KEY DISTRIBUTION

Hoi‐Kwong Lo

Quantum key distribution (QKD) allows two parties to communicate in absolute security based on the fundamental laws of physics. Up till now, it is widely believed that unconditionally secure QKD based on standard Bennett-Brassard (BB84) protocol is limited in both key generation rate and distance because of imperfect devices. Here, we solve these two problems directly by presenting new protocols that are feasible with only current technology. Surprisingly, our new protocols can make fiber-based QKD unconditionally secure at distances over 100km (for some experiments, such as GYS) and increase the key generation rate from O(η2) in prior art to O(η) where η is the overall transmittance. Our method is to develop the decoy state idea (first proposed by W.-Y. Hwang in "Quantum Key Distribution with High Loss: Toward Global Secure Communication", Phys. Rev. Lett. 91, 057901 (2003)) and consider simple extensions of the BB84 protocol. This part of work is published in "Decoy State Quantum Key Distribution", . We present a general theory of the decoy state protocol and propose a decoy method based on only one signal state and two decoy states. We perform optimization on the choice of intensities of the signal state and the two decoy states. Our result shows that a decoy state protocol with only two types of decoy states—a vacuum and a weak decoy state—asymptotically approaches the theoretical limit of the most general type of decoy state protocols (with an infinite number of decoy states). We also present a one-decoy-state protocol as a special case of Vacuum+Weak decoy method. Moreover, we provide estimations on the effects of statistical fluctuations and suggest that, even for long distance (larger than 100km) QKD, our two-decoy-state protocol can be implemented with only a few hours of experimental data. In conclusion, decoy state quantum key distribution is highly practical. This part of work is published in "Practical Decoy State for Quantum Key Distribution", . We also have done the first experimental demonstration of decoy state quantum key distribution, over 15km of Telecom fibers. This part of work is published in "Experimental Decoy State Quantum Key Distribution Over 15km", .

International Journal of Quantum Information•Nov 1, 2005•16 citations

Security of Quantum Key Distribution with Realistic Devices

Xiongfeng Ma

We simulate quantum key distribution (QKD) experimental setups and give out some improvement for QKD procedures. A new data post-processing protocol is introduced, mainly including error correction and privacy amplification. This protocol combines the ideas of GLLP and the decoy states, which essentially only requires to turn up and down the source power. We propose a practical way to perform the decoy state method, which mainly follows the idea of Lo's decoy state. A new data post-processing protocol is then developed for the QKD scheme with the decoy state. We first study the optimal expected photon number mu of the source for the improved QKD scheme. We get the new optimal mu=O(1) comparing with former mu=O(eta), where eta is the overall transmission efficiency. With this protocol, we can then improve the key generation rate from quadratic of transmission efficiency O(eta2) to O(eta). Based on the recent experimental setup, we obtain the maximum secure transmission distance of over 140 km.

arXiv:quant-ph/0503057•Mar 5, 2005•14 citations

Practical decoy state for quantum key distribution

Xiongfeng Ma, Bing Qi, Yi Bing Zhao +1 more

Decoy states have recently been proposed as a useful method for substantially improving the performance of quantum key distribution (QKD). Here, we present a general theory of the decoy state protocol based on only two decoy states and one signal state. We perform optimization on the choice of intensities of the two decoy states and the signal state. Our result shows that a decoy state protocol with only two types of decoy states---the vacuum and a weak decoy state---asymptotically approaches the theoretical limit of the most general type of decoy state protocol (with an infinite number of decoy states). We also present a one-decoy-state protocol. Moreover, we provide estimations on the effects of statistical fluctuations and suggest that, even for long-distance (larger than 100 km) QKD, our two-decoy-state protocol can be implemented with only a few hours of experimental data. In conclusion, decoy state quantum key distribution is highly practical.

arXiv:quant-ph/0503005•Physical Review A•Jul 20, 2005•1,139 citations

Improve the efficiency of a practical quantum key distribution system

Bing Qi, Yi Bing Zhao, Xiongfeng Ma +2 more

The performance of a practical quantum key distribution (QKD) system is often limited by the multi-photon state emission of its source and the dark counts of its detectors. Here, we present two methods to improve its performance. The first method is decoy state QKD: the sender randomly sends out weak coherent states with various average photon numbers (which are named as signal state and decoy states). In [14,15], we have performed the first experimental implementation of decoy state QKD over 15km and 60km respectively, thus dramatically increasing the distance and secure key generation rate of practical QKD systems. Our work has been followed up by many research groups worldwide [16-18]. The second scheme is QKD with "dual detectors" [19]: the legitimate receiver randomly uses either a fast (but noisy) detector or a quiet (but slow) detector to measure the incoming quantum signals. The measurement results from the quiet detector can be used to upper bound the eavesdropper's information, while the measurement results from the fast detector are used to generate a secure key. We applied this idea to various QKD protocols. Simulation results demonstrated significant improvements in both BB84 protocol with ideal single photon source and Gaussian-modulated coherent states protocol.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 11, 2007•2 citations
Decoy states have recently been proposed as a useful method for substantially improving the performance of quantum key distribution (QKD) protocols when a coherent-state source is used. Previously, data postprocessing schemes based on one-way classical communications were considered for use with decoy states. In this paper, we develop two data postprocessing schemes for the decoy-state method using two-way classical communications. Our numerical simulation (using parameters from a specific QKD experiment as an example) results show that our scheme is able to extend the maximal secure distance from 142km142\phantom{\rule{0.3em}{0ex}}\mathrm{km}142km (using only one-way classical communications with decoy states) to 181km181\phantom{\rule{0.3em}{0ex}}\mathrm{km}181km. The second scheme is able to achieve a 10% greater key generation rate in the whole regime of distances. We conclude that decoy-state QKD with two-way classical postprocessing is of practical interest.
The use of decoy states in quantum key distribution (QKD) has provided a method for substantially increasing the secret key rate and distance that can be covered by QKD protocols with practical signals. The security analysis of these schemes, however, leaves open the possibility that the development of better proof techniques or better classical postprocessing methods might further improve their performance in realistic scenarios. In this paper, we derive upper bounds on the secure key rate for decoy-state QKD. These bounds are based basically only on the classical correlations established by the legitimate users during the quantum communication phase of the protocol. The only assumption about the possible postprocessing methods is that double click events are randomly assigned to single click events. Further, we consider only secure key rates based on the uncalibrated device scenario which assigns imperfections such as detection inefficiency to the eavesdropper. Our analysis relies on two preconditions for secure two-way and one-way QKD. The legitimate users need to prove that there exists no separable state (in the case of two-way QKD) or that there exists no quantum state having a symmetric extension (one-way QKD) that is compatible with the available measurements results. Both criteria have been previously applied to evaluate single-photon implementations of QKD. Here we use them to investigate a realistic source of weak coherent pulses. The resulting upper bounds can be formulated as a convex optimization problem known as a semidefinite program which can be efficiently solved. For the standard four-state QKD protocol, they are quite close to known lower bounds, thus showing that there are clear limits to the further improvement of classical postprocessing techniques in decoy-state QKD.
Quantum key distribution (QKD) allows two parties to communicate in absolute security based on the fundamental laws of physics. Up till now, it is widely believed that unconditionally secure QKD based on standard Bennett-Brassard (BB84) protocol is limited in both key generation rate and distance because of imperfect devices. Here, we solve these two problems directly by presenting new protocols that are feasible with only current technology. Surprisingly, our new protocols can make fiber-based QKD unconditionally secure at distances over 100km (for some experiments, such as GYS) and increase the key generation rate from O(η2) in prior art to O(η) where η is the overall transmittance. Our method is to develop the decoy state idea (first proposed by W.-Y. Hwang in "Quantum Key Distribution with High Loss: Toward Global Secure Communication", Phys. Rev. Lett. 91, 057901 (2003)) and consider simple extensions of the BB84 protocol. This part of work is published in "Decoy State Quantum Key Distribution", . We present a general theory of the decoy state protocol and propose a decoy method based on only one signal state and two decoy states. We perform optimization on the choice of intensities of the signal state and the two decoy states. Our result shows that a decoy state protocol with only two types of decoy states—a vacuum and a weak decoy state—asymptotically approaches the theoretical limit of the most general type of decoy state protocols (with an infinite number of decoy states). We also present a one-decoy-state protocol as a special case of Vacuum+Weak decoy method. Moreover, we provide estimations on the effects of statistical fluctuations and suggest that, even for long distance (larger than 100km) QKD, our two-decoy-state protocol can be implemented with only a few hours of experimental data. In conclusion, decoy state quantum key distribution is highly practical. This part of work is published in "Practical Decoy State for Quantum Key Distribution", . We also have done the first experimental demonstration of decoy state quantum key distribution, over 15km of Telecom fibers. This part of work is published in "Experimental Decoy State Quantum Key Distribution Over 15km", .
We simulate quantum key distribution (QKD) experimental setups and give out some improvement for QKD procedures. A new data post-processing protocol is introduced, mainly including error correction and privacy amplification. This protocol combines the ideas of GLLP and the decoy states, which essentially only requires to turn up and down the source power. We propose a practical way to perform the decoy state method, which mainly follows the idea of Lo's decoy state. A new data post-processing protocol is then developed for the QKD scheme with the decoy state. We first study the optimal expected photon number mu of the source for the improved QKD scheme. We get the new optimal mu=O(1) comparing with former mu=O(eta), where eta is the overall transmission efficiency. With this protocol, we can then improve the key generation rate from quadratic of transmission efficiency O(eta2) to O(eta). Based on the recent experimental setup, we obtain the maximum secure transmission distance of over 140 km.
Decoy states have recently been proposed as a useful method for substantially improving the performance of quantum key distribution (QKD). Here, we present a general theory of the decoy state protocol based on only two decoy states and one signal state. We perform optimization on the choice of intensities of the two decoy states and the signal state. Our result shows that a decoy state protocol with only two types of decoy states---the vacuum and a weak decoy state---asymptotically approaches the theoretical limit of the most general type of decoy state protocol (with an infinite number of decoy states). We also present a one-decoy-state protocol. Moreover, we provide estimations on the effects of statistical fluctuations and suggest that, even for long-distance (larger than 100 km) QKD, our two-decoy-state protocol can be implemented with only a few hours of experimental data. In conclusion, decoy state quantum key distribution is highly practical.
The performance of a practical quantum key distribution (QKD) system is often limited by the multi-photon state emission of its source and the dark counts of its detectors. Here, we present two methods to improve its performance. The first method is decoy state QKD: the sender randomly sends out weak coherent states with various average photon numbers (which are named as signal state and decoy states). In [14,15], we have performed the first experimental implementation of decoy state QKD over 15km and 60km respectively, thus dramatically increasing the distance and secure key generation rate of practical QKD systems. Our work has been followed up by many research groups worldwide [16-18]. The second scheme is QKD with "dual detectors" [19]: the legitimate receiver randomly uses either a fast (but noisy) detector or a quiet (but slow) detector to measure the incoming quantum signals. The measurement results from the quiet detector can be used to upper bound the eavesdropper's information, while the measurement results from the fast detector are used to generate a secure key. We applied this idea to various QKD protocols. Simulation results demonstrated significant improvements in both BB84 protocol with ideal single photon source and Gaussian-modulated coherent states protocol.