India demonstrates first 5.56-km free-space quantum-secure communication link

India has successfully demonstrated its first free-space Quantum Key Distribution (QKD) link over a distance of 5.56 km. The field trial, conducted on the night of September 27-28, was a collaborative effort between QNu Labs, the Bhaskaracharya National Institute for Space Applications and Geo-informatics (BISAG-N), and IIT Gandhinagar.

The trial utilized QNu Labs’ Pointing, Acquisition and Tracking system to establish a secure channel between BISAG-N and IIT Gandhinagar. Technical results showed a stable Quantum Bit Error Rate of below 5 per cent, with secure encryption keys generated at a rate of 230-260 bits per second. These keys were integrated with the Vedic Kavach platform, which uses post-quantum cryptography to enable end-to-end encryption and decryption.

This demonstration is a significant step toward developing quantum-secure communication networks. Unlike traditional fiber-based methods, free-space QKD transmits keys through optical channels in open air, which is essential for future long-distance and satellite-based quantum communication systems. The architecture combines hardware-based QKD via the Armos device with software-based post-quantum cryptography to ensure security even if the physical quantum channel is temporarily unavailable.