## 3 Results  
A 24-h window was selected to obtain a comprehensive snapshot of the stability and performance of the QKD-enabled encryption tunnel. This duration was chosen to encompass various operational conditions, including peak usage periods and potential environmental variations affecting system performance. Critical QKD parameters were systematically monitored throughout this interval, including the key generation rate, error rates in key distribution, and the system's resilience against potential quantum and classical attacks. These parameters were analyzed to assess the robustness of the QKD infrastructure and its efficiency in maintaining secure communication under various conditions. The findings provided insights into the reliability of QKD technology for real-world applications, identifying its strengths and potential areas for improvement in practical implementations. Figure 2 shows the data collected on the key rate maintained consistently during the 24 h monitoring period. This key rate proved sufficient to maintain a stable quantum key-encrypted channel, ensuring continuous and secure communication. The stability of the key rate indicates that the QKD system could generate and distribute quantum keys at a rate that met or exceeded the requirements to maintain the encrypted channel. This sustained key rate is critical for ensuring that the encryption remains robust and fluctuations in key availability do not compromise secure data transmission. The ability to maintain this rate over an extended period underscores the system's reliability and its suitability for practical, long-term deployment in secure communication networks. For all of the following figures, the horizontal axis consists of time, in total, 24 h. The vertical axis label is given at the bottom of each figure and consists of absolute values. Values are recorded in 30-s intervals. Thus, each hour has 120 records that form a graphical representation of values over time. Figure 1: Experimental setup diagram. Figure 3 shows the Quantum Bit Error Rate (QBER) and the consistently sustained levels throughout the 24 h testing period. The QBER, a critical parameter in evaluating the quality of the quantum key distribution, remained within acceptable limits, indicating that the system maintained high fidelity in key transmission. Throughout the monitoring period, no anomalies or deviations were detected, suggesting that the quantum channel remained stable and free of disturbances that could degrade the quality of the transmitted keys. This stability in QBER is crucial because it reflects the system's capability to resist noise and interference, thereby ensuring the integrity and security of the quantum key distribution process. The absence of anomalies further validates the reliability of the QKD system under continuous operation, reinforcing its potential for secure and uninterrupted communication in real-world applications. Figure 4 shows the visibility parameter that is consistently maintained throughout the 24-h monitoring period. Visibility, a key metric in quantum key distribution systems, measures the contrast between the quantum states representing '0' and '1' bits. High visibility indicates a clear distinction between these states, which is essential for accurate  
Figure 3: QBER. Figure 2: Key rate. key generation and reduces the likelihood of errors during key transmission. The data show that visibility remained high and stable, suggesting that the quantum states were well defined and that the system was operating efficiently. This sustained high visibility is crucial for ensuring the reliability and security of the quantum key distribution process, as it minimizes the potential for key errors and enhances the system's resistance to eavesdropping. The consistent visibility observed during the testing period indicates that the QKD system was operating under optimal conditions, with minimal influence from external factors, such as environmental noise or hardware imperfections.