Quantum Cryptography, Quantum Networking

QNu Labs and partners send quantum keys 5.56km through the air

Avatar of Ivy Delaney
October 5, 2026 by Ivy Delaney

QNu Labs, BISAG-N, and IIT Gandhinagar have established India’s first 5.56 kilometer free-space Quantum Key Distribution (QKD) link, integrating quantum security with a post-quantum cryptography platform. The trial, conducted between BISAG-N and IIT Gandhinagar, achieved a stable secure key rate of 230-260 bits per second while maintaining a Quantum Bit Error Rate (QBER) below 5%, demonstrating practical feasibility for real-world applications, the company says.

Sunil Gupta, Co-founder and CEO of QNu Labs, stated that quantum security will become meaningful at scale only when technologies can move beyond controlled laboratory environments and operate across real communication infrastructure. This successful demonstration combines QKD hardware with BISAG-N’s Vedic Kavach software, layering quantum key distribution with post-quantum cryptography for enhanced security.

5.56km Free-Space QKD Link Established Between BISAG-N and IIT Gandhinagar

QNu Labs’ Pointing, Acquisition and Tracking (PAT) system maintained a 1550 nm quantum channel during a 5.56 kilometer free-space QKD trial between BISAG-N and IIT Gandhinagar, demonstrating the feasibility of long-distance quantum communication in realistic conditions. The system achieved coarse pointing accuracy of 5 microradians and fine pointing accuracy up to 0.1 microradians, compensating for atmospheric disturbances and physical movement to keep the quantum link aligned, according to BISAG-N.

This level of precision was critical for sustaining the link and achieving a stable QBER below 5%, a key metric for secure key generation. The trial, conducted on the nights of September 27-28, 2026, generated a secure key rate of 230-260 bits per second using the DPS-Decoy QKD protocol, producing approximately one fresh 256-bit key each second.

This key was then delivered via the ETSI GS QKD 014 interface to BISAG-N’s Vedic Kavach post-quantum cryptography-enabled browser and web server, allowing for an end-to-end test of encrypted message transmission and decryption. The architecture deliberately layered QKD with post-quantum cryptography, creating a resilient system that remains protected even if the quantum channel is temporarily unavailable.

Dr. Vinay Thakur, DG BISAG-N, said that 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 collaboration between QNu Labs, BISAG-N, and IIT Gandhinagar represents a step toward practical quantum communication infrastructure, providing a foundation for longer links, multiple nodes and eventual satellite-based quantum communication, strengthening critical infrastructure against emerging quantum era security threats.

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.

Dr. Vinay Thakur, DG BISAG-N
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free-space optics post-quantum cryptography quantum key distribution
Avatar of Ivy Delaney

Ivy Delaney

Ivy Delaney has been working with neural networks and machine learning since the mid-nineties, back when a couple of hidden layers and a long afternoon of training counted as ambitious. She has watched the field go from academic curiosity to the thing quietly running underneath everything, and she brings that long view to quantum computing. For Quantum Zeitgeist she covers the ground where the two fields meet. That means quantum machine learning and the variational algorithms it leans on, and it also means the less glamorous but more interesting story of classical machine learning already doing real work inside quantum machines, decoding error-correcting codes, calibrating noisy hardware and learning the error models that simulators depend on. She writes about the hardware those algorithms have to run on too, and about the post-quantum cryptography scramble that the same hardware has set off. Her stories typically start with the paper, whether that is peer-reviewed work, conference proceedings or an arXiv preprint, with the source linked so you can hold a claim up against the research it came from. She is unimpressed by benchmarks that will not say what they beat, and by demonstrations that only work in the press release.

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