A Review of Quantum Key Distribution Systems under Environmental Noise

Quantum Key Distribution (QKD) enables information-theoretically secure communication by exploiting quantum mechanics, making it a promising solution for nextgeneration network security. However, its practical deployment is hindered by environmental noise such as channel loss, background photons, atmospheric turbulence, and device imperfections, which degrade secret key rates and system reliability. This review analyzes the impact of noise on QKD systems across fiber, free-space, and hybrid communication channels, and compares the robustness of major protocols including discrete-variable (DV-QKD), continuous-variable (CV-QKD), entanglement-based, and one-sided device-independent (1SDIQKD) schemes. It further surveys recent advancements in noise mitigation, including adaptive optimization, machine learning–based techniques, and improved optical architectures. Additionally, the integration of QKD into secure network infrastructures is discussed, focusing on key management and resilience against noise-assisted attacks. The study highlights current challenges and highlights future directions for developing scalable and noise-tolerant QKD systems.