India has demonstrated its first free-space quantum key distribution link over 5.56 kilometres, a key step toward secure quantum communication networks.

The field trial was carried out by QNu Labs with BISAG-N and IIT Gandhinagar on the night of September 27-28. It set up a secure quantum channel between BISAG-N and IIT Gandhinagar.

The system used QNu Labs’ pointing, acquisition and tracking setup. It achieved a stable quantum bit error rate below 5 percent and generated secure keys at 230 to 260 bits per second.

The keys were fed into BISAG-N’s Vedic Kavach platform, which uses post-quantum cryptography. Test messages were encrypted and decrypted end to end successfully.

The trial combined two security layers: QNu Labs’ Armos hardware device, which sends keys through open-air optical channels, and Vedic Kavach’s software-based post-quantum cryptography.

“This integration marks a significant step toward practical quantum-resilient communication systems,” said BISAG-N director general Vinay Thakur.

QNu Labs CEO Sunil Gupta said the 5.56-km trial paves the way for longer-distance networks and satellite-based quantum communication.