Error mitigation is one of the key challenges in realising the full potential of quantum cryptographic protocols. Consequently, there is a lot of interest in adapting techniques from quantum error correction (QEC) to improve the robustness of quantum cryptographic protocols. In this work, we benchmark the performance of different QKD protocols on noisy quantum devices, with and without error correction. We obtain the secure key rates of BB84, B92 and BBM92 QKD protocols over a quantum channel that is subject to amplitude-damping noise. We demonstrate, theoretically and via implementations on the IBM quantum processors, that B92 is the optimal protocol under amplitude-damping and generalized amplitude-damping noise. We then show that the security of the noisy BBM92 protocol crucially depends on the type and the mode of distribution of an entangled pair. Finally, we implement an error-corrected BB84 protocol using dual-rail encoding on a noisy quantum processor, and show that the dual-rail BB84 implementation outperforms the conventional BB84 in the presence of noise. Our secure key rate calculation also takes into account the effects of CNOT imperfections on the error rates of the protocols.
Error mitigation is one of the key challenges in realising the full potential of quantum cryptographic protocols. Consequently, there is a lot of interest in adapting techniques from quantum error correction (QEC) to improve the robustness of quantum cryptographic protocols. In this work, we benchmark the performance of different QKD protocols on noisy quantum devices, with and without error correction. We obtain the secure key rates of BB84, B92 and BBM92 QKD protocols over a quantum channel that is subject to amplitude-damping noise. We demonstrate, theoretically and via implementations on the IBM quantum processors, that B92 is the optimal protocol under amplitude-damping and generalized amplitude-damping noise. We then show that the security of the noisy BBM92 protocol crucially depends on the type and the mode of distribution of an entangled pair. Finally, we implement an error-corrected BB84 protocol using dual-rail encoding on a noisy quantum processor, and show that the dual-rail BB84 implementation outperforms the conventional BB84 in the presence of noise. Our secure key rate calculation also takes into account the effects of CNOT imperfections on the error rates of the protocols.
Quantum Key Distribution is theoretically possible secure communication through the use of quantum-mechanical principles, such as superposition, measurement disturbance, and others. The BB84 and E91 protocols provide security by leveraging quantum principles against classical eavesdropping; nevertheless, the current implementation of QKD is vulnerable to photon-number-splitting attacks, imperfections in the devices used, and environmental quantum noise. Improving practical resistance to all of those is crucial for providing secure real-life use of QKD. Extending the current state-of-the-art through further development of research on eavesdropper detection and improvement of qubit-based security mechanisms, this research aims to develop the state-of-the art further by introducing a decoy-state BB84 framework and analyzing the behavior of such a system under realistic quantum noise. To find solutions to these problems, the current research will try to adopt the decoy-state BB84 model and analyze the system behavior under realistic quantum noise scenarios. So, the proposed approach, a standard BB84 protocol, will first be formulated and then further enhanced with decoy-state pulse generation to handle the vulnerabilities due to multi-photon pulses. Models like depolarizing noise, amplitude damping, and measurement errors will be used as real-world quantum channels. The model performance will be measured in terms of various performance metrics such as Key agreement ratio, Quantum Bit Error rate, and secure key rate for different qubit lengths. Scalability analysis and validation based on IBM quantum hardware will also be performed in order to measure the impact of real-world device noise on the reliability of generated keys.
Quantum cryptography was proposed as a counter to the capacity of quantum computers to break classical cryptosystems. A broad subclass of quantum cryptography, called quantum key distribution (QKD), relies on quantum mechanical process for secure distribution of the keys. Quantum channels are inherently noisy, and therefore these protocols will be susceptible to noise as well. In this paper, we study the performance of two QKD protocols — BB84 and E91 under amplitude damping error. We show that while E91 protocol loses its security immediately due to loss of entanglement, the performance of BB84 protocol reduces to random guessing with increasing time. Next, we consider the action of an Eve on the BB84 protocol under amplitude damping noise, who is restricted to guessing the outcome of the protocol only. Under this restriction, we show that Eve can still do better than random guessing when equipped with the characteristics of the noisy channel. Finally, we propose a modification of the BB84 protocol which retains the security of the original protocol, but ensures that Eve cannot get any advantage in guessing the outcome, even with complete channel information.
Quantum computing poses significant threats to conventional cryptographic techniques such as RSA and AES, motivating the need for quantum secure communication methods. Quantum Key Distribution (QKD) offers information theoretic security based on fundamental quantum principles. This paper presents a simulation-based analysis of well-known QKD protocols, namely BB84, B92, and E91, using the IBM Qiskit framework. Realistic quantum channel effects, including noise, decoherence, and eavesdropping, are modeled to evaluate protocol performance. Key metrics such as error rate, secret key generation, and security characteristics are analyzed and compared. The study highlights practical challenges in QKD implementation, including hardware limitations and channel losses, and discusses insights toward scalable and robust quantum communication systems. The results support the feasibility of QKD as a promising solution for secure communication in the quantum era.
Quantum key distribution (QKD) is a method that enables secure communication between two parties by applying the ideas of quantum physics. By minimizing information leakage that can happen during the key generation process, privacy amplification is a technique used to improve the security of QKD. The technique involves processing the raw key obtained from QKD through a randomization procedure to remove any residual information that may have been leaked during the quantum transmission. While privacy amplification can significantly improve the security of QKD, the effectiveness of the technique is limited by the quality of the initial raw key. The BB84 QKD protocol has been improved with the proposed En-BB84 protocol, which includes built-in authentication and integrity checks. The En-BB84 protocol ensures secure distribution of secret keys and protects against tampering by attackers. Key distillation and error correction techniques are employed to extract a shorter, more secure shared secret key and correct errors introduced during qubit transmission. The protocol utilizes a four-state QKD approach, expanding on the traditional two-state scheme of BB84. A simulation of the En-BB84 protocol is demonstrated using a quantum circuit implemented with Qiskit in Python. The circuit employs various gates and operations, including Hadamard, CX, controlled swap, and RZ gates, to achieve encoding and error correction. Furthermore, we have designed a better protocol with improved error rates by incorporating improvisations on the BB84 protocol. Experimental results indicate the successful integration of the B92 error correction scheme into the modified BB84 protocol, enhancing the security and performance of QKD systems.
Quantum Key Distribution (QKD) provides information-theoretic security by exploiting the principles of quantum mechanics. Among QKD protocols, the BB84 scheme remains the most widely adopted for both theoretical research and practical implementation. A critical parameter determining the reliability and security of BB84 is the Quantum Bit Error Rate (QBER), which quantifies errors in the sifted key arising from channel noise or potential eavesdropping. This paper presents a systematic review and analysis of QBER within the BB84 protocol, examining its calculation, statistical estimation methods, and role in detecting eavesdropping activity. Simulation results, corroborated by reported experimental observations, reveal a near-linear relationship between eavesdropping intensity and QBER, with values approaching 25% under full intercept-resend attacks. Four confidence interval estimation methods, Wald, Wilson, Clopper-Pearson, and Hoeffding's inequality, are compared for robust QBER analysis in finite-key scenarios. Protocol enhancements, including decoy-state methods, hybrid cryptographic models, and quantum-resistant authentication, are discussed as mechanisms to mitigate errors and strengthen resilience across fiber, free-space, underwater, and satellite QKD systems. Open challenges in distinguishing noise-induced errors from malicious eavesdropping, and the role of adaptive error correction and machine-learning-assisted QBER estimation in future quantum networks, are identified as key directions for further research.
Quantum Key Distribution (QKD) in underwater environments presents unique challenges due to the inherent properties of water as a quantum channel. This work contributes to the broader study of underwater quantum communication, with a focus on enhancing the robustness of QKD protocols through quantum error correction (QEC). This study models the underwater quantum channel to assess the feasibility of performing QKD in such conditions. This research aims to enhance the performance of the QKD through additional QEC that should mitigate errors introduced by the underwater channel. We employ an erasure and noise model to simulate the underwater environment inspired by the prior work of Rizk et al. (2025), excluding depolarisation effects, to evaluate the channel’s impact on quantum communication. The findings aim to offer valuable insights into implementing secure quantum communication underwater and demonstrate how QEC can influence the implementation of QKD protocols in such settings.