Quantum key distribution (QKD), which enables the secure distribution of symmetric keys between two legitimate parties, is highly useful in future network security. An access network that connects multiple end users with one network backbone can be combined with QKD to build security for end users in a scalable and cost-effective way. In this paper, we show that a downstream-access network can be implemented using continuous-variable (CV) QKD. The security analysis is conducted independently with other network nodes, which greatly relax the trustfulness requirement on the network nodes. The security is then obtained against other network parties even when the quantum signals are broadcast throughout the network. The passive beam splitter is sufficient to deterministically distribute the quantum signals, and standard CV QKD systems can be directly fitted in the downstream-access network, which makes it more applicable for practical implementations. Numerous simulation results are provided to demonstrate the performance of the CV QKD downstream-access network, where up to 64 end users are shown to be feasible to access the network. We provide the security-analysis framework for realizing CV QKD in the downstream-access network, which will boost the diversity for constructing practical CV QKD networks.
Quantum key distribution (QKD), which enables the secure distribution of symmetric keys between two legitimate parties, is highly useful in future network security. An access network that connects multiple end users with one network backbone can be combined with QKD to build security for end users in a scalable and cost-effective way. In this paper, we show that a downstream-access network can be implemented using continuous-variable (CV) QKD. The security analysis is conducted independently with other network nodes, which greatly relax the trustfulness requirement on the network nodes. The security is then obtained against other network parties even when the quantum signals are broadcast throughout the network. The passive beam splitter is sufficient to deterministically distribute the quantum signals, and standard CV QKD systems can be directly fitted in the downstream-access network, which makes it more applicable for practical implementations. Numerous simulation results are provided to demonstrate the performance of the CV QKD downstream-access network, where up to 64 end users are shown to be feasible to access the network. We provide the security-analysis framework for realizing CV QKD in the downstream-access network, which will boost the diversity for constructing practical CV QKD networks.
Quantum key distribution (QKD) which enables the secure distribution of symmetric keys between two legitimate parties is of great importance in future network security. Access network that connects multiple end-users with one network backbone can be combined with QKD to build security for end-users in a scalable and cost-effective way. Though previous QKD access networks are all implemented in the upstream direction, in this paper, we prove that downstream access network can also be constructed by using continuous-variable (CV) QKD. The security of the CV-QKD downstream access network is analyzed in detail, where we show the security analysis is secure against other parties in the network. The security analysis we proved corresponds to the downstream access network where only passive beamsplitter is sufficient to distribute the quantum signals and no other active controls are demanded. Moreover, standard CV-QKD systems can be directly fitted in the downstream access network, which makes it more applicable for practical implementations. Numerous simulation results are provided to demonstrate the performance of the CV-QKD downstream access network, where up to 64 end-users are shown to be feasible to access the network. Our work provides the security analysis framework for realizing QKD in the downstream access network which will boost the diversity for constructing practical QKD networks.
An quantum access network, connecting multiple end users and a backbone network in a scalable and cost-effective way with tree or star structures, is suitable to combine with continuous-variable quantum key distribution for network security. Under the realistic condition, in a passive optical network in optical distribution network achieved by a practical passive beam splitter, it is hard to divide the signal into 1/n parts evenly. To well quantify the impact of the imperfection, we modify the formula for secret key rate calculation with the imperfection effect and conduct numerical simulations. The results indicate that if the communication parties neglect this imperfection, Eve can attack the entire network and attain information without the parties’ awareness.
Nowadays, network speeds are increasing rapidly and network security is a growing concern. Quantum key distribution (QKD) can provide unconditionally secure keys at the physical layer for communication networks. The implementation of high-speed QKD quantum networks is important for the security of modern high-speed networks. Here, for the first time, we realized a four-user high-speed downstream access network experiment. The repetition frequency of the system is 100 MHz, considering block size of108, four users achieved secret key rates of 430 kbps, 450 kbps, 150 kbps, and 130 kbps at channel attenuations of 4.4 dB, 4.2 dB, 5.6 dB, and 5.8 dB, respectively. In addition, we find that the block size, the number of users, and the channel attenuation have a significant impact on the system performance in real systems. When the block size is108and the number of user nodes is four, the maximum channel attenuation that can be supported is about 6 dB. Our experimental results demonstrate the feasibility of multi-user downstream CV-QKD access networks, further advancing the practical application of quantum networks in real-world environments.
Quantum secure communication technology, grounded in the principles of quantum mechanics, has revolutionized traditional cryptographic methods, which predominantly rely on mathematical algorithms and logical transformations. Quantum key distribution (QKD) facilitates the secure sharing of symmetric keys between legitimate parties, ensuring the integrity and confidentiality of information in communication channels. Among various QKD schemes, continuous variable quantum key distribution (CV-QKD) has emerged as a viable alternative to the more established discrete variable quantum key distribution (DV-QKD). CV-QKD boasts several advantages, including straightforward deployment, reduced operational costs, and stable signal quality, positioning it as a significant component of the quantum communication landscape. Quantum noise stream cipher (QNSC) represents a technique that employs redundant data streams to encrypt plaintext. Notably, QNSC shares structural similarities with the optical path used in quantum key distribution, allowing for compatibility with existing QKD infrastructure. Furthermore, the keys generated through quantum key distribution ensure absolute security, enabling them to substitute the data streams produced by pseudo-random sequences traditionally used in classical encryption schemes. This substitution enhances the overall security framework of the quantum noise stream encryption approach. The quantum access network (QAN) extends quantum key distribution capabilities from point-to-point connections to point-to-multipoint configurations, thereby becoming an essential component of contemporary network architectures. By interlinking multiple end users with a network backbone, quantum access networks can seamlessly integrate with quantum key distribution protocols. This integration offers a cost-effective and scalable solution for user access to the network. Extensive experimental verifications have demonstrated the viability of downstream access networks, indicating that the merging of quantum access network structures with quantum stream encryption technologies can yield a comprehensive quantum experimental platform. On this platform, security keys are derived through quantum key distribution, which subsequently facilitates the encryption of plaintext information. Notably, experimental validations involving eight users have been successfully executed on this platform, underscoring its practical applicability and effectiveness.
Quantum networks based on quantum key distribution ensure the security which is guaranteed by the fundamental laws of quantum physics between multiple parties. The discrete-modulation (DM) continuous-variable quantum key distribution (CV-QKD) protocols have the characteristics of simple implementation and compatibility with classical digital communication, making them very suitable for deployment in large-scale communication networks. However, the actual communication network has a huge communication capacity and a large number of units. To solve this problem, we propose a multiple-quadrature-amplitude-modulation (MQAM) DM protocol with a numerical method and complete the security analysis of the DM protocol in a downstream-access network situation. By introducing an extra dimension of signal modulation, the high-order modulated MQAM protocol greatly improves the number of supported units and the key rate of each unit. We give the results of a 16 quadrature amplitude modulation CV-QKD protocol in a downstream-access network which achieves 64 supported network units even in the case of high excess noise, which shows the application prospects of high-order discrete-modulation CV-QKD in network security.
In recent years, continuous-variable quantum key distribution (CV-QKD) has become a promising paradigm for enabling secure communication among multiple end users sharing the same telecommunication backbone. CV-QKD with reverse reconciliation naturally enables scalability from conventional point-to-point links to quantum access networks based on passive quantum broadcasting channels. Here, we report an experimental demonstration on an active 1:4 multi-user CV quantum network (QN) in the finite-size regime. With 1.25⋅109 coherent states exchanged on each 11km quantum channel, the highest performance for secret key generation totaling 1.9⋅10−1 bits/channel use. Furthermore, we investigate adaptable CV-QN protocols that comprehensively allow network operation in various security and key rates requirements of individual users. The results establish the practical security of CV-QN compatible with existing telecommunication for broad deployment, and allowing additional degree of freedom for connected end users in existing infrastructures.