National – QNu Labs (www.qnulabs.com), a global leader in end-to-end hybrid quantum cybersecurity solutions, along with the Bhaskaracharya National Institute for Space Applications and Geo-informatics (BISAG-N), and IIT Gandhinagar, have successfully completed a 5.56 km free-space Quantum Key Distribution (QKD) field trial, marking India’s first free-space QKD link at the 5 km scale. The field trial demonstrates the ability to establish and maintain a quantum-secured communication link over open atmosphere while integrating QKD generated keys with a post-quantum cryptography (PQC) enabled application environment.
Conducted on the night of September 27–28, 2026, the trial established a 5.56 km free-space quantum communication link between BISAG-N and IIT Gandhinagar, with QNu Labs’ Pointing, Acquisition and Tracking (PAT) system maintaining the 1550 nm quantum channel. Using the DPS-Decoy QKD protocol, the link achieved a stable QBER below 5% and a secure key rate of 230–260 bps. The trial also demonstrated the end-to-end integration of QKD with BISAG-N’s Vedic Kavach PQC enabled browser and web server, with 256 bit keys delivered through the ETSI GS QKD 014 interface, enabling a test message to be encrypted, transmitted and successfully decrypted.
The trial combined two complementary layers of quantum security. QNu Labs’ QKD technology provided hardware-based quantum key distribution over the free-space optical channel, while Vedic Kavach provided a software layer based on post-quantum cryptography and quantum random number generation (QRNG). The architecture was designed so that the application remains protected even if the physical quantum channel is temporarily unavailable, providing a practical approach to building quantum-resilient communication systems.
Sunil Gupta, Co-founder and CEO, QNu Labs, said, “Quantum security will become meaningful at scale only when technologies can move beyond controlled laboratory environments and operate across real communication infrastructure. This field trial shows that QKD, supported by precise optical pointing and tracking, can be deployed over a multi-kilometre free-space link and integrated with a post-quantum security layer. The successful 5.56 km demonstration is an important step towards developing longer-distance quantum-secure networks and exploring architectures that can eventually support multiple nodes and satellite-based quantum communication.”
The technical performance of the trial was enabled by QNu Labs’ PAT system, which used coarse pointing through a gimbal and fine steering at a 100 Hz tracking bandwidth to maintain alignment between the two terminals. The system achieved coarse pointing accuracy of 5 microradians and fine pointing accuracy of up to 0.1 microradians, enabling the quantum channel to remain aligned despite atmospheric conditions and physical movement along the optical path.
Cmde Manish Tripathi (Retd.), In-charge, ISTF, IIT-G said, “The successful demonstration of a 5.56 km free-space QKD link provides a valuable field environment for advancing practical quantum communication technologies. The collaboration brings together academic research, indigenous technology and real-world experimentation, and demonstrates how these capabilities can be integrated to address the emerging requirements of secure communications.”
Dr. Vinay Thakur, DG BISAG-N said, “The integration of Vedic Kavach with QNu Labs’ QKD technology demonstrates the potential of combining post-quantum cryptography with quantum key distribution as complementary layers of security. The successful end-to-end application test is an important step towards developing practical quantum-resilient communication architectures that can evolve with emerging security requirements.”
At a secure key rate of 230–260 bps, the link generated approximately one fresh 256 bit key every second while maintaining QBER below 5%, demonstrating the viability of a hybrid QKD and PQC architecture in a field environment. The trial provides a foundation for advancing towards longer links, multiple nodes and, eventually, satellite based quantum communication, while strengthening the resilience of critical communication infrastructure against emerging quantum era security threats.
