## 2 Related Work  
### Quantum Key Distribution (QKD)  
In recent years, the intersection of quantum communication has attracted considerable attention for its potential to address information security challenges and enable innovative applications. The security and performance of future communication networks, especially 5G networks, can be greatly improved by using QKD technology. [PERSON] et al. [8] proposed a 5G private network based on quantum communication technology for smart grid applications. They pointed out the information security challenges posed by 5G, and proposed a QKD strategy based on the Quality of Service (QoS) to improve the confidentiality of the 5G private power network application scheme. Experimental results showed that the service quality of 5G private network meets the communication requirements of power grid services, the actual transmission delay of the power grid simulation dispatch data is about 1s, and there is no packet loss. [PERSON] et al. [9] provided an overview of the potential applications of QKD for future communication technology, as well as the challenges and standardisation efforts in this field. They also reviewed the main challenges that QKD faces in terms of secret key rate, distance, size, cost, and practical security. They also emphasised the importance of standardisation for QKD and presented several ongoing efforts by different organisations to develop common specifications, protocols, and test methods for QKD systems. In addition, they pointed out that wireless communication is an essential component of future quantum communication networks that can provide wireless access and mobility. However, most QKD research has been concentrated on the optical channel model and point-to-point communication links. Therefore, more research work is needed to investigate the feasibility of QKD in wireless channels and multi-point communication links. [PERSON] et al. [1] presented a comprehensive overview of research directions in QKD that enable secure communication based on the principles of quantum physics. Their discussion focused on three key aspects. Firstly, they explored QKD integration in 5G networks, highlighting the potential of combining QKD with the next generation of mobile networks. Secondly, they examined measurement-device-independent QKD, a technique that improves the security and reliability of QKD. Lastly, they discussed hybrid QKD networks, which involve the combination of different types of QKD systems to improve compatibility, efficiency, and robustness. In conclusion, they emphasized the significance and promising prospects of QKD technologies in the rapidly evolving field of quantum information science. [PERSON] et al. [2] presented the applications, challenges, and prospects of QKD technology in 5G networks. They discussed several typical applications of QKD in 5G networks, including quantum virtual private network, quantum metropolitan area network, and quantum backbone network. They also analysed the benefits and challenges associated with these applications, as well as the current implementation progress. Several studies have explored the use of quantum technologies to enhance the security and performance of wireless networks. The subsequent part of this section presents a literature review of some of the recent works that are related to our research. The review covers three aspects: node placement optimization, data encryption scheme, and attacker detection technique. [PERSON] et al. [10] proposed a novel enhanced quantum particle swarm optimization algorithm, which aims to minimize energy consumption and maximize network lifetime by optimising node placement in heterogeneous industrial IoT. [PERSON] et al. [11] presented a secure data encryption scheme tailored for 5G. To establish secure communication, the scheme used QKD to securely exchange encryption keys between the sender and the receiver.