Quantum Key Distribution Research Articles

Development of superposition-based quantum key distribution protocol in decentralized full mesh networks

The object of this research is the security of communication networks, particularly in decentralized, multi-user environments where robust data protection and integrity are critical. The issue under discussion is the rising vulnerability of conventional cryptography systems resulting from ever complex cyberattacks and the expected risks presented by quantum computing possibilities. The development of a QKD protocol employing quantum superposition to improve data security and resilience against both present and future quantum-based cyber-attacks is demonstrated by the achieved results of this work. Achieving scalability and autonomous eavesdropping detection, this protocol lets several communication nodes securely exchange randomly produced keys without centralized management. A quick analysis of the results reveals that main elements influencing the great durability, security, and adaptability of the protocol are quantum superposition and its distributed character. Without centralized authority, the characteristics of the obtained results – especially the use of optical components, detectors, and quantum sources in conjunction with classical communication channels – solve the problem of ensuring data confidentiality and integrity in a multi-user environment. This protocol's practical reach covers safe communication applications in both public and private sectors, therefore addressing situations calling for strong data protection against modern cyberattacks. Conditions for practical application include settings like government, financial, or health-related interactions when safe information flow is crucial. This QKD system offers a future-ready security solution for high-stakes environments and represents notable advancement toward protecting data from quantum and conventional attacks

A hybrid encryption framework leveraging quantum and classical cryptography for secure transmission of medical images in IoT-based telemedicine networks

In the era of the Internet of Things (IoT), the transmission of medical reports in the form of scan images for collaborative diagnosis is vital for any telemedicine network. In this context, ensuring secure transmission and communication is necessary to protect medical data to maintain privacy. To address such privacy concerns and secure medical images against cyberattacks, this research presents a robust hybrid encryption framework that integrates quantum, and classical cryptographic methods. The proposed framework not only secure medical data against cyber threats but also protects the secret security keys. Initially, a Quantum Key Distribution (QKD) is employed to generate a shared key, which is then used to secure the symmetric keys via One-Time Pad (OTP) encryption. Next, bit-planes are extracted from each color component. The rows and columns of the extracted bit-planes are scrambled using random sequences which are generated by a 6D hyperchaotic Chen system and the Ikeda map. To further increase confusion in the original data, multiple-step pixel scrambling operations such as pixel shuffling, pixel value shuffling, and rotational and flipping operations are implemented. After the confusion phase, a combination of affine transformations with non-linear functions, Discrete Cosine Transform (DCT) with complex modulation, Discrete Wavelet Transform (DWT) with random phase modulation, bilinear transformation, and nonlinear polynomial mapping are employed to create diffusion in the scrambled components. These multiple encryption operations aim to maximize randomness in the final ciphertext image. Additionally, to reduce computational complexity, only the Most Significant Bit-Planes (MSBs) are encrypted, as they contain more than 94% of the plaintext information. Several experimental results and analyses are conducted to assess the proposed encryption framework, including entropy analysis, key sensitivity analysis, correlation analysis lossless analysis, and histogram analysis. Furthermore, the framework is tested against various cyberattacks such as brute-force attacks, clipping attacks, and noise attacks on the ciphertext images, to demonstrate its resilience against such threats.

Single-Photon Detectors for Quantum Integrated Photonics

Single-photon detectors have gained significant attention recently, driven by advancements in quantum information technology. Applications such as quantum key distribution, quantum cryptography, and quantum computation demand the ability to detect individual quanta of light and distinguish between single-photon states and multi-photon states, particularly when operating within waveguide systems. Although single-photon detector fabrication has been established for some time, integrating detectors with waveguides using new materials with suitable structural and electronic properties, especially at telecommunication wavelengths, creates more compact source-line-detector systems. This review explores the state of the art of single-photon detector research and examines the potential breakthroughs offered by novel low-dimensional materials in this field.

Anti-Interference High Speed Modulation Decoder for Quantum Key Distribution

Abstract Quantum key distribution is gradually moving towards network applications. It is important to improve the performance of quantum key distribution systems such as photonic integration for compact systems, the stability resistant to environmental disturbance, high key rate, and high efficiency. In this letter, we propose an orthogonal-polarizations-exchange reflector Michelson interferometer model to solve quantum channel disturbance caused by environment. Based on this model, we design a Sagnac-reflector Michelson interferometer decoder, and verify the performance of the decoder by constructing an interference system. The interference fringe visibility is greater than 98% for all four coding phases in 625MHz. The results show that the decoder can resist environmental interference and support high speed modulation frequency. In addition, the anti-interference decoder without magneto-optical device is suitable for the realization of photonic integration, which is the development trend of the next generation quantum communication devices.

Enhancing e-KYC Security and Privacy: Harnessing Quantum Computing and Blockchain in Web 3.0

By implementing a successful and effective Electronic-Know Your Customer (e-KYC) infrastructure, conventional defects and expenses may be greatly reduced. Strong authentication procedures are used by existing e-KYC solutions to guarantee safety and confidentiality. However, these technologies have shortcomings like as key administration expenses and dependency on encryption. We suggest a revolutionary strategy that integrates blockchain technology, Web 3.0, and quantum computing to get around these restrictions. In this research, we show how current e-KYC processes could possibly be improved, making them faster and more reliable, by integrating Web 3.0 with quantum computing. Our solution makes it simple to quickly verify several consumers, increasing productivity. We provide improved safety for online requests, transcending the weaknesses inherent in traditional encryption techniques by utilizing quantum computing technology and applying the concept of quantum encryption key methodology. We contribute to the development of safe and private solutions by addressing the shortcomings of the present e-KYC systems. The results of our research show how Web 3.0 and quantum computer technology have the power to completely alter the e-KYC environment.

Advantage distillation for quantum key distribution

Abstract Quantum key distribution promises information-theoretically secure communication, with data post-processing playing a vital role in extracting secure keys from raw data. While hardware advancements have significantly improved practical implementations, optimizing post-processing techniques offers a cost-effective avenue to enhance performance. Advantage distillation, which extends beyond standard information reconciliation and privacy amplification, has proven instrumental in various post-processing methods. However, the optimal post-processing remains an open question. Therefore, it is important to develop a comprehensive framework to encapsulate and enhance these existing methods. In this work, we propose an advantage distillation framework for quantum key distribution, generalizing and unifying existing key distillation protocols. Inspired by entanglement distillation, our framework not only integrates current techniques but also improves upon them. Notably, by employing classical linear codes, we achieve higher key rates, particularly in scenarios where one-time pad encryption is not used for post-processing. Our approach provides insights into existing protocols and offers a systematic way for further enhancements in quantum key distribution.

Mask-coding-assisted continuous-variable quantum direct communication with orbital angular momentum multiplexing

Abstract Quantum secure direct communication (QSDC) is an approach of communication to transmitting secret messages based on quantum mechanics. Different from the quantum key distribution, secret messages can be transmitted directly on quantum channel with QSDC. Higher channel capacity and noise suppression capabilities are key to achieving longdistance quantum communication. Here we report a continuous-variable QSDC scheme based on mask-coding and orbital angular momentum, in which the mask-coding is employed to protect the security of the transmitting messages and to suppression the influence of excess noise. And the combination of orbital angular momentum and the information block transmission can effectively improve the secrecy capacity. In the 800 information blocks × 1310 bits length 10-km experiment, the results show that the statistical average of bit error rate reached 0.38%, and the system excess noise is 0.0184 SNU, and the final secrecy capacity is 6.319×106 bps. Therefore, this scheme reduces error bits while increasing secrecy capacity, providing a solution for long-distance large-scale quantum communication, which has capacity of transmitting text, images, and other information of reasonable size.

Routing Algorithm Within the Multiple Non-Overlapping Paths' Approach for Quantum Key Distribution Networks.

We develop a novel key routing algorithm for quantum key distribution (QKD) networks that utilizes a distribution of keys between remote nodes, i.e., not directly connected by a QKD link, through multiple non-overlapping paths. This approach focuses on the security of a QKD network by minimizing potential vulnerabilities associated with individual trusted nodes. The algorithm ensures a balanced allocation of the workload across the QKD network links, while aiming for the target key generation rate between directly connected and remote nodes. We present the results of testing the algorithm on two QKD network models consisting of 6 and 10 nodes. The testing demonstrates the ability of the algorithm to distribute secure keys among the nodes of the network in an all-to-all manner, ensuring that the information-theoretic security of the keys between remote nodes is maintained even when one of the trusted nodes is compromised. These results highlight the potential of the algorithm to improve the performance of QKD networks.

Independent-optical-frequency-comb-powered 546-km field test of twin-field quantum key distribution

Independent-optical-frequency-comb-powered 546-km field test of twin-field quantum key distribution

Quantum Network Infrastructure

AbstractGlobal quantum state distribution has applications in many areas, one of which is global key distribution for secure communications in an era of the threat of quantum computing. Long‐distance quantum key distribution requires a global network of optical relay stations, ground stations, and quantum memories. In this study, why quantum memories should be operated in space as untrusted nodes is presented. In addition to quantum key distribution, quantum memories in space are an enabling technology for distributed quantum sensor systems. The requirements for distributed sensors are outlined and the current technology readiness level of relevant systems is referenced. Finally, the possibility of an emerging quantum internet, enabling the coherent combination of quantum computers around the world, is addressed.

Enhancing noise suppression of phase estimation in continuous-variable quantum key distribution with discrete modulation.

Accurately estimating phase is crucial in continuous-variable quantum key distribution systems, directly impacting the final secret key rate. In previous systems that utilize the local local oscillator, phase estimation is closely tied to the amplitude and signal-to-noise ratio (SNR) of the pilot signal. As SNR decreases, so does the accuracy of phase estimation, leading to increased excess noise and a potential loss of the system's secret key rate. The SNR of the pilot signal is constrained by the optical source power, which tends to approach 0 dB, particularly over long distances. Enhancing the accuracy of phase estimation under conditions of low SNR for pilot signals is highly challenging, especially in long-distance quantum key distribution. Our paper proposes two digital filter methods: the unscented Kalman filtering (UKF) and the Savitzky-Golay filtering (SGF) for phase estimation, which effectively mitigates the effects of additive noise. The approach applies to digital systems and therefore holds particular advantages in systems based on discrete-modulation (DM) protocols. Through simulations and practical implementation based on DM protocols, we find that the digital filter scheme is capable of accurately estimating phase, especially in scenarios with low SNR of the pilot signal. The conventional method fails to achieve an effective secret key rate, whereas the digital-filter-based scheme achieves a secret key rate of almost 30 kbps over a 20 km fiber link with a repetition frequency of 5 MHz under conditions where the SNR of the pilot signal is around 0 dB.

Reconfigurable entanglement distribution network based on pump management of a spontaneous four-wave mixing source.

Leveraging the unique properties of quantum entanglement, quantum entanglement distribution networks support multiple quantum information applications and are essential to the development of quantum networks. However, practical implementation poses fundamental challenges to network scalability and flexibility. Here, we propose a reconfigurable entanglement distribution network scheme based on tunable multipump excitation of a spontaneous four-wave mixing (SFWM) source and a time-sharing method. We characterize the two-photon correlation under different pump conditions to demonstrate the effect of pump degenerate and pump nondegenerate SFWM processes on the two-photon correlation and its tunability. Then, as a benchmark application, a 10-user fully connected quantum key distribution network is established in a time-sharing way with triple pump lights. Our results provide a promising networking scheme for large-scale entanglement distribution networks owing to its scalability, functionality, and reconfigurability.

Post-measurement pairing quantum key distribution with local optical frequency standard

Abstract The idea of post-measurement coincidence pairing simplifies substantially long-distance, repeater-like quantum key distribution (QKD) by eliminating the need for tracking the differential phase of the users’ lasers. However, optical frequency tracking remains necessary and can become a severe burden in future deployment of multi-node quantum networks. Here, we resolve this problem by referencing each user’s laser to an absolute frequency standard and demonstrate a practical post-measurement pairing QKD with excellent long-term stability. We confirm the setup’s repeater-like behavior and achieve a finite-size secure key rate (SKR) of 15.94 bit/s over 504 km fiber, which overcomes the absolute repeaterless bound by 1.28 times. Over a fiber length 100 km, the setup delivers an impressive SKR of 285.68 kbit/s. Our work paves the way towards an efficient muti-user quantum network with the local frequency standard.

Discrete-variable quantum key distribution services hosted in legacy passive optical networks [Invited

Fiber-based quantum key distribution (QKD) systems are mature and commercialized, but their integration into existing optical networks is crucial for their widespread use, in particular in passive optical networks (PONs) if end-to-end quantum-secured communications are to be addressed. While discrete-variable QKD coexistence with classical channels is well-studied in point-to-point links, its performance in point-to-multipoint topologies like PONs has received less attention. We thus developed a numerical tool to estimate quantum-available bandwidth and maximum link lengths for QKD systems in single-fiber PON architectures in coexistence with GPON, XG-PON, NG-PON2, and HS-PON standards. The QKD channel performance is obtained by setting thresholds on the quantum bit error rate and the secret key rate, ultimately limited by spontaneous Raman scattering noise and high optical distribution network losses. We perform a comparison between the performance obtained assuming the asymptotic infinite-key generation rate or taking into account actual implementations in the finite-key regime. We evidence that proper design rules can be obtained as a function of both classical and quantum system parameters to support end-to-end quantum security services in existing optical networks.

Parameters Optimization of Decoy-State Phase-Matching Quantum Key Distribution Based on the Nature-Inspired Algorithms

Abstract Phase-Matching quantum key distribution (PM-QKD) has achieved significant results in practical applications; however, real-time communication necessitates the dynamic adjustment and optimization of key parameters during the communication process. In this paper, we predict the parameters of PM-QKD using Nature-inspired Algorithms (NIAs), with results obtained from an Exhaustive Traversal Algorithm (ETA) serving as the benchmark. We mainly study the parameter optimization effects of the two NIAs which are Ant Colony Optimization (ACO) and Genetic Algorithm (GA). Meanwhile the configuration of the inherent parameters of these algorithms in decoy-state PM-QKD is discussed. The simulation results indicate that the parameters obtained by ACO exhibits superior convergence and stability, while the results of the GA are relatively scattered. Nevertheless, over 97% of the key rates predicted by both algorithms are highly consistent with the optimal key rate, with the relative error of key rates remaining below 10%. Furthermore, NIAs not only keep power consumption below 8W, but also require three orders of magnitude less computing time than ETA.

The finite-size effect on continuous-variable quantum key distribution in the Terahertz band

We conducted a study to evaluate the performance of Terahertz Continuous Variable Quantum Key Distribution (THz CVQKD) systems in atmospheric conditions with the finite-size effect. Our research delved into the secure key rates and transmission distances of THz CVQKD for four protocols, all based on Gaussian coherent states, under the threat of collective Gaussian attacks. These protocols include reverse reconciliation with homodyne detection, direct reconciliation with homodyne detection, reverse reconciliation with heterodyne detection, and direct reconciliation with heterodyne detection. Our findings revealed distinctive key rates across various THz frequencies and protocols. However, the finite-size effect had a diminishing impact on the key rates of CVQKD in all scenarios. Fortunately, by harnessing a substantial number of keys exceeding 1012 and optimizing modulation variance, both the key rates and transmission distances of THz CVQKD can be significantly extended. This research contributes to advancing the practicality of THz CVQKD technology.

Correction: Quantum private query protocol based on counterfactual quantum key distribution with noiseless attack

Correction: Quantum private query protocol based on counterfactual quantum key distribution with noiseless attack

Improved reference-frame-independent quantum key distribution with intensity fluctuations

Abstract Reference-frame-independent quantum key distribution (RFI-QKD) can avoid real-time calibration operation of reference frames and improve the efficiency of the communication process. However, due to imperfections of optical devices, there will inevitably exist intensity fluctuations in the source side of the QKD system, which will affect the final secure key rate. To reduce the influence of intensity fluctuations, an improved 3-intensity RFI-QKD scheme is proposed in this paper. After considering statistical fluctuations and implementing global parameter optimization, we conduct corresponding simulation analysis. The results show that our present work can present both higher key rate and a farther transmission distance than the standard method.

Effect of pseudo-random number on the security of quantum key distribution protocol

Abstract 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 pseudo-random 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.

A Quantum Encryption Algorithm based on the Rail Fence Mechanism to Provide Data Integrity

The rapid development of quantum computer technology poses an increasing threat to conventional encryption algorithms, and accordingly, more advanced security practices need to be developed. The current paper presents an innovative quantum cryptographic mechanism that combines classical encryption techniques with quantum principles such as superposition, entanglement, and uncertainty to enhance data security in digital communication. The proposed scheme, defined as Enhanced Quantum Key Distribution (EQKD), demonstrates superior performance in key metrics, including Quantum Bit Error Rate (QBER), fidelity, key distribution rate, and resilience to eavesdropping. In particular, EQKD achieves lower QBER and higher fidelity over longer distances while also enhancing key generation efficiency and increasing the probability of detecting eavesdropping attempt. These findings highlight the effectiveness of EQKD in improving the security and reliability of quantum cryptographic systems.