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.

翻译：量子密钥分发（QKD）通过利用量子力学原理提供信息理论安全性。在各QKD协议中，BB84方案仍是理论研究和实际应用中最广泛采用的方法。决定BB84可靠性与安全性的关键参数是量子比特误码率（QBER），该参数量化了由信道噪声或潜在窃听导致的对基筛选密钥中的错误。本文系统性地综述并分析了BB84协议中的QBER，探讨其计算方法、统计估计手段及在检测窃听活动中的作用。仿真结果（与已报道的实验观测一致）表明，窃听强度与QBER呈近似线性关系，在完全截取重发攻击下可接近25%。针对有限密钥场景下的稳健QBER分析，本文比较了四种置信区间估计方法：Wald法、Wilson法、Clopper-Pearson法以及Hoeffding不等式法。还讨论了协议增强机制，包括诱骗态方法、混合密码模型及量子抗性认证，以降低错误率并增强光纤、自由空间、水下及卫星QKD系统的鲁棒性。在区分噪声诱导错误与恶意窃听方面尚存的挑战，以及自适应纠错和机器学习辅助QBER估计在未来量子网络中的作用，被确定为未来研究的关键方向。