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.
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.
Quantum key distribution (QKD) enables secure underwater communications essential for maritime infrastructure. Underwater optical channels introduce substantial photon loss (erasures) and ambient noise that degrade QKD performance. This paper investigates whether two four-qubit Calderbank-Shor-Steane (CSS) quantum error correction codes (QECC) mitigate these impairments in vertical underwater communication BB84 QKD protocol. After developing a comprehensive stochastic channel model incorporating photon loss, geometric spreading, and solar noise, we assess the viability of QECC through the analytical study of the quantum bit error rate (QBER) and the secure key rate (SKR) with and without security depending on the signal-to-noise ratio (SNR) validated against Monte Carlo simulations. The standard four-qubit CSS code achieves a 3 dB SNR gain at the QBER 11% security threshold; the discard code variant achieves 4.5 dB. However, QECC includes an encoding overhead that reduces the SKR. We demonstrate a crucial relationship between the SKR and the probability of arrival of the sent photon. Analysis shows that QECC is beneficial exclusively in marginal SNR regimes; at high SNR, raw BB84 dominates. For an ocean Type III Jerlov water scenario with sunlight coming from the sun located at the top of the atmosphere, we identify operational depth-range windows where QECC enables communication otherwise infeasible. This analysis establishes that error correction deployment must be scenario-dependent: extend operational range at the cost of throughput when SNR is marginal, or prioritize key generation rates at high SNR.
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 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.
Underwater wireless communication is rapidly advancing, finding applications in diverse fields such as oceanography, defense, and commercial ventures. However, ensuring security in such transmissions is crucial due to the sensitive nature of the data involved and the challenges posed by the underwater environment. While classical encryption techniques provide some level of security, the emergence of quantum computing presents opportunities and challenges. Quantum key distribution (QKD) offers theoretically unbreakable encryption, making it an attractive solution. Extending QKD capabilities to underwater environments is a significant endeavor in this context. This paper explores the feasibility of applying an entanglement-based non-coherent QKD protocol inspired by the BBM92 protocol to underwater visible light communication (VLC)/QKD systems. We investigate the system’s design criteria and analyze its secret key performance, addressing challenges such as water absorption and turbulence-induced fading, focusing on addressing unauthorized receiver attacks. Through analysis and the considered case study, the feasibility and efficacy of this approach are explored, contributing to the advancement of secure underwater communications.
Underwater optical channels pose significant challenges to the security and reliability of quantum communication systems due to absorption and scattering. In this paper, we investigate the BBM92 entanglement-based quantum key distribution (QKD) protocol under realistic underwater channel conditions. Photon pairs are prepared in non-maximally entangled states, and the underwater propagation medium is modeled as a quantum channel incorporating both amplitude-damping and depolarizing effects, described within the Kraus operator formalism. The protocol performance is evaluated in terms of quantum bit error rate (QBER) and secret key rate (SKR), analyzed as functions of the entanglement degree and channel degradation parameters. Closed-form analytical expressions for the QBER and SKR are derived for the proposed channel model and validated through Monte Carlo simulations. The proposed framework is then applied to various realistic underwater scenarios, considering different water types, namely clear ocean, coastal, and turbid water, as well as varying atmospheric conditions.
This paper investigates the optimization of distributed quantum key distribution (QKD) protocols with a focus on resilience enhancement. The core claim centers around improving both the security and efficiency of key distribution by strategically incorporating redundancy and error correction mechanisms. The proposed approach leverages the unique characteristics of quantum communication protocols, specifically utilizing redundant quantum channels and advanced error-correcting codes to achieve robust key exchange. The method addresses the limitations of existing QKD protocols in the face of channel noise and potential eavesdropping attacks. Mathematical models are presented to illustrate the key concepts and design choices. The optimization strategy is designed to maximize key rates while simultaneously mitigating the impact of channel imperfections, ultimately leading to more secure and reliable quantum key distribution systems. This work provides a theoretical framework for resilient QKD, offering a foundation for future implementations and further research in this critical field.