Exploring Quantum Key Distribution for Secure Communication in High-Altitude Platforms

In the contemporary digital era, ensuring the security of sensitive data and communication is of paramount significance. Encryption methods have been widely employed to safeguard data transmission over public channels. However the exponential growth in computational power has led to concerns regarding the potential vulnerability of encryption methods. Consequently, breaking encryption poses a significant threat to data privacy. In response to these challenges, the field of quantum cryptography has emerged as a promising solution, offering a fundamentally unbreakable approach to secure communication. One of the key advancements in quantum cryptography is quantum key distribution (QKD). This secure communication mechanism relies on the principles of quantum mechanics to generate encryption keys, enabling secure information exchange between parties. This paper focuses on analysis of the quantum channel between the optical ground station (OGS) and the high-altitude platform System (HAPS). The research involves a meticulous examination and optimization of various system parameters such as performance secret key rate (SKR), electronic noise, modulation variance, and zenith angle. Remarkably, the SKR for a HAPS operating at a vertical altitude of 20 km, with a zenith angle of 20 degrees and a pulse generation rate of $500 \mathbf{M H z}$, is approximately $84 \mathbf{~ M b} / \mathbf{s}$ and 44.5 $\mathbf{M b} / \mathbf{s}$ for homodyne and heterodyne detection, respectively. This information highlights the potential of quantum cryptography in providing secure communication channels that are resilient to cryptographic attacks.