Sunday 06 April 2025
The quest for secure communication has led scientists to explore uncharted territories, and their latest venture is a fascinating example of this pursuit. Researchers have successfully demonstrated the ability to transmit quantum keys over a mixed optical fiber link, which includes both underground and aerial segments.
The team employed two commercial Quantum Key Distribution (QKD) systems with different encoding schemes – one based on polarization and the other on phase and time-bin encoding. The goal was to test the performance of these QKD systems in a real-world setting, where environmental factors like wind and temperature changes can affect the signal quality.
The experiment involved transmitting quantum keys over a 30-kilometer link, consisting of 14 kilometers of underground fiber and 16 kilometers of aerial fiber. The team used commercial QKD systems from ThinkQuantum and IDQuantique, which were connected to two data centers in Athens, Greece.
The results showed that the phase and time-bin encoding system was more resilient to environmental fluctuations, as it maintained stable operation across all tested attenuation levels (10 dB, 23 dB, and 30 dB). In contrast, the polarization-based system required more frequent initialization due to constant changes in the state of polarization. This highlights the importance of considering the specific properties of each encoding scheme when designing QKD systems for real-world applications.
One of the most significant findings was the impact of aerial fiber on the performance of the QKD systems. The team observed a 50% drop in Secret Key Rate (SKR) and an increase in Quantum Bit Error Rate (QBER) when using the polarization-based system over the mixed fiber link compared to the in-lab setup. This demonstrates the need for fast polarization compensation mechanisms to correct basis misalignments caused by environmental fluctuations.
The experiment also shed light on the importance of considering the specific properties of each encoding scheme when designing QKD systems for real-world applications. The phase and time-bin encoding system’s stability was attributed to its ability to encode information in both consecutive pulses, making it less susceptible to changes in the state of polarization.
This research has significant implications for the development of secure communication networks. As quantum computing becomes increasingly prevalent, the need for secure key exchange will only grow. By understanding how different encoding schemes perform in real-world scenarios, researchers can develop more robust and reliable QKD systems that can withstand environmental fluctuations and ensure the security of sensitive information.
The use of mixed optical fiber links, including both underground and aerial segments, is an important consideration for future QKD system designs.
Cite this article: “Quantum Key Distribution Over Aerial Fibers: Bridging the Gap Between Security and Practicality”, The Science Archive, 2025.
Quantum Key Distribution, Qkd, Mixed Optical Fiber Links, Underground Fibers, Aerial Fibers, Encoding Schemes, Polarization, Phase Time-Bin, Secret Key Rate, Quantum Bit Error Rate
