Towards Ultra-Secure 6G Networks: A Comprehensive Review on Quantum Key Distribution Techniques and Applications

The advent of sixth-generation (6 G) networks introduces transformative communication paradigms characterized by ultra-low latency, massive device connectivity, and unprecedented reliability. These developments also expose networks to complex and dynamic cybersecurity threats and challenge the adequacy of traditional encryption methods against the emerging capabilities of quantum computing. Utilizing the fundamental laws of quantum mechanics, Quantum Key Distribution (QKD) provides unconditional security of communications by enabling the detection of eavesdropping attempts. We systematically analyze existing QKD protocols, designs, and application scenarios while addressing technological limitations and potential solutions. In addition, we explore the future directions necessary to realize scalable, efficient, and practical quantum-secured 6 G networks. Our findings emphasize the strategic importance of QKD as a cornerstone technology for building ultra-secure, quantumresilient communication infrastructures in the era of 6 G.