## 1 Introduction  
In the modern digital age, protecting the confidentiality and integrity of communication data is essential. While modern cryptographic algorithms are effective in classical computing contexts, they are increasingly susceptible to the emerging field of quantum computing. Quantum computers can solve certain problems greatly faster than classical computers. For instance, [PERSON]'s algorithm can easily factor large integers and solve the discrete logarithm problem, which places the security of widely used cryptographic algorithms such as Rivest-Shamir-Adleman (RSA) and elliptic curve cryptography (ECC) in risk [1, 2, 3]. Similarly, symmetric key algorithms are also challenged by the [PERSON]'s algorithm that can speed up brute-force search by reducing their security strength. As these advancements in quantum technologies continue to progress, the demand for innovative cryptographic solutions is becoming increasingly urgent. Post-quantum cryptography (PQC) is a developing area that provides cryptographic algorithms that are resistant to quantum attacks [4]. Simultaneously, quantum key distribution (QKD) protocols are being developed to utilize the principles of quantum mechanics to facilitate secure key exchange, thereby achieving unconditional security. Quantum computers pose a great challenge to traditional cryptographic methods, as noted in [5]. However, PQC algorithms, including lattice-based cryptography, code-based cryptography, hash-based cryptography, and multivariate cryptography [6; 7; 8; 9; 10; 11; 12; 13; 14], provide strong protection against the computational abilities of quantum adversaries. These adversaries can easily solve classical hard problems like integer factorization and discrete logarithms. It is important to highlight an advantage of PQC encryption algorithms, which is their built-in resilience against attacks from quantum computers as emphasized by [15]. In the complex realm of QKD, security is deeply rooted in the principles of quantum mechanics such as [PERSON]'s uncertainty principle and the no-cloning theorem, explained by [16; 17] respectively. These principles act as guardians, promptly detecting any attempts at interception and strengthening the security of distributed keys. The importance of PQC in ensuring the security of communication channels is underscored by [18], given the reliance of QKD on the distribution of secret keys between parties. Moreover, the vulnerabilities revealed in modern cryptographic methods, particularly when faced with quantum threats [19], show the meaning of adopting PQC methodologies. By enhancing authentication and encryption processes, PQC schemes offer an improved approach for integrating new participants into QKD, enhancing accessibility while reinforcing secure communication. The crucial role of PQC in QKD systems is further emphasized by diverse experimental efforts, similar to those suggested by [4]. This research aims to establish a secure system for key exchange by using PQC schemes in the classic channel of QKD. Other objectives include finding the optimal balance between security and communication speed among different security levels of CRYSTALS-Kyber, CRYSTALS-Dilithium, and Falcon, which are finalists in the National Institute of Standards and Technology (NIST) Post-Quantum Cryptography Standardization project. The quantum channel of QKD is simulated with Qiskit, a comprehensive and well-supported tool in the field of quantum computing. The results will guide organizations in selecting optimal security level for their QKD systems to achieve a reliable balance between efficiency and security. We will achieve this by providing a detailed analysis of the performance of these three algorithms with RSA. Our findings will show that the implemented PQC schemes effectively improve the reliability of communication by addressing security challenges and having the RSA performance. This study makes several significant contributions.