Quantum Key Distribution (QKD) is a technique that allows for secure communication between two parties by utilizing quantum mechanics. One of the most important parameters of QKD systems is the maximum distance over which secure key distribution can be achieved. Over the years, researchers have been working to improve the distance over which QKD can be implemented.
The distance over which QKD can be implemented depends on various factors such as the type of QKD protocol used, the type of fiber optic cable or satellite used, and the amount of attenuation that occurs during transmission. In recent years, researchers have been successful in increasing the distance of QKD by using various techniques such as entanglement-based QKD, satellite-based QKD, and free-space QKD.
In Feb 2022, University of Science and Technology of China Scientists broke a QKD record over 830-km optical fiber. And in 2023, ID Quantique shared an approach to testing QKD communication locally by using loops of fiber optic cable 40km long.
Quantum Internet Alliance, under the €1-billion Quantum Flagship project, is developing Q*Bird, an offering the building blocks for the quantum communication infrastructure in the Netherlands and Europe. Q*Bird is a “unique Quantum Key Distribution (QKD) technology [which] offers the following advantages: multipoint-to-multipoint connectivity; cost-effective scaling; improved security and it is future proof: our devices are designed to be upgradable with the most advanced quantum network technology.”
Going forward, leveraging higher satellites will offer greater coverage with more frequency with the potential for QKD communication between two ground stations 10,000 km apart.