Ultra-high data rates, efficient use of the terahertz spectrum, and significant connectivity are anticipated as Sixth Generation (6G) wireless communication emerges. However, traditional cryptographic algorithms like RSA and Elliptic Curve Cryptography, which are currently employed in wireless networks, are seriously threatened by the quick development of quantum computing. Future 6G systems must incorporate quantum-safe security measures to allay this worry. The incorporation of Quantum Key Distribution (QKD) into the physical layer of 6G communication networks is investigated in this paper. To facilitate secure key exchange and identify eavesdropping, QKD makes use of quantum concepts like superposition, entanglement, and the no-cloning theorem. Realistic wireless channel conditions are used to analyze the BB84 and E91 protocols. A proposed 6G channel model incorporates Nakagami-m fading, additive white Gaussian noise, and path loss. Detector noise and channel disturbances are taken into account when modeling the Quantum Bit Error Rate (QBER). In an OFDM framework, MATLAB simulations evaluate the secure key rate performance with respect to signal- to-noise ratio, transmission distance, and noise probability. The findings highlight the potential of QKD for secure 6G communications by showing that secure key generation is possible when the QBER stays below the theoretical threshold. Index Terms 5G and 6G wireless communications, Quantum Key Distribution, Fading Channels.