QNu Labs Demonstrates 5.56 km Free-Space QKD Link
Key Takeaways
Field trial: QNu Labs, BISAG-N and IIT Gandhinagar ran a 5.56 km free-space QKD link on the night of September 27-28, 2026.
Link result: The ministry reported a quantum bit error rate below 5% and secure keys at 230-260 bits per second.
Security stack: Keys fed BISAG-N Vedic Kavach, which combines post-quantum cryptography with quantum random number generation.
QNu Labs, the Bhaskaracharya National Institute for Space Applications and Geo-informatics (BISAG-N) and IIT Gandhinagar demonstrated a 5.56 km free-space QKD link on the night of September 27-28, 2026, the Ministry of Electronics and Information Technology said in an October 3 release. The trial sent quantum signals through open air between BISAG-N and IIT Gandhinagar in Gujarat, then used the resulting keys to encrypt and decrypt test messages on BISAG-N Vedic Kavach. MeitY described the work as India’s first free-space QKD link at this distance. Earlier Indian open-air tests covered shorter paths, so the claim is a distance milestone rather than the country’s first free-space quantum communication experiment.
Field Trial Link Performance
The partners used the QNu Labs Armos QKD device and a pointing, acquisition and tracking system to hold a free-space optical channel across 5.56 km. The Press Information Bureau reported a stable quantum bit error rate below 5% and secure-key generation at 230-260 bits per second. The rate describes key material, not message throughput. A 256-bit key would take on the order of one second at the upper end of the reported range. The ministry did not publish the QKD protocol, wavelength, detector type or atmospheric conditions. Dataquest, which carried the trial on October 3, likewise attributed those figures to MeitY.
Free-space quantum key distribution sends single-photon or weak-coherent signals through the atmosphere instead of fibre. Alignment, turbulence and background light set the practical limit. The night-time window fits standard practice for reducing solar background. The result is a field test of one path, not an operational network.
| Element | Specification |
|---|---|
| Link distance | 5.56 km free-space optical path between BISAG-N and IIT Gandhinagar |
| Trial window | Night of September 27-28, 2026 |
| QKD hardware | QNu Labs Armos with pointing, acquisition and tracking |
| Error rate | Quantum bit error rate below 5% |
| Key rate | 230-260 bits per second of secure key material |
| Application layer | BISAG-N Vedic Kavach with post-quantum cryptography and quantum random number generation |
| Message test | End-to-end encryption and decryption of test messages |
Hybrid Security and Institutional Roles
Armos supplied the hardware QKD layer. Vedic Kavach supplied post-quantum cryptography and quantum random number generation, and the teams used the combined stack for end-to-end test-message encryption and decryption. MeitY said the architecture is meant to remain usable when the physical quantum channel is temporarily unavailable. The release does not name the post-quantum algorithm or the interface between the QKD keys and the software platform.
BISAG-N, an autonomous scientific society under MeitY, works on space applications, satellite communication and geo-informatics. Commodore Manish Tripathi (Retd.), in charge of ISTF at IIT Gandhinagar, said the campus gave the trial a field setting for academic and indigenous hardware work. Sunil Gupta, co-founder and chief executive of QNu Labs, said the 5.56 km result supports longer-distance networks and satellite-based quantum communication. Dr. Vinay Thakur, director general of BISAG-N, described the Vedic Kavach integration as a step toward practical quantum-resilient communication. QNu Labs, founded in 2016, is based in Bengaluru.
Comparable Free-Space QKD Demonstrations
The Gandhinagar path sits behind several published free-space and satellite QKD results, and ahead of India’s earlier open-air tests.
On June 16, 2025, DRDO and IIT Delhi demonstrated entanglement-based free-space quantum secure communication over more than 1 km on the IIT Delhi campus, with a secure key rate near 240 bits per second and a quantum bit error rate under 7%, the Defence Ministry said. On March 22, 2021, ISRO reported a 300 metre free-space quantum key distribution demonstration between buildings at the Space Applications Centre in Ahmedabad. The National Quantum Mission target calls for satellite-based secure quantum communication between ground stations up to 2,000 km apart, plus a 2,000 km inter-city fibre QKD network.
Outside India, a University of Padua and ThinkQuantum team reported an 18 km intermodal free-space QKD field trial in npj Quantum Information on August 26, 2026, with secret-key rates near 200 bits per second on room-temperature detectors and near 1 kilobit per second on superconducting detectors. China launched Micius in 2016 and later reported satellite-to-ground QKD, then a China-Austria relay with ground stations about 7,600 km apart. The smaller Jinan-1 microsatellite, launched in 2022, supported a real-time QKD link between Beijing and Stellenbosch published in Nature on March 19, 2025, with 1.07 million secure bits in one pass over a 12,900 km ground-station separation. SpeQtral launched the SpeQtre quantum CubeSat in November 2025 with UK RAL Space and is using optical ground stations in Singapore and the United Kingdom. The Indian trial is a terrestrial step toward the same satellite problem, not a satellite pass.
Bottom Line
The Gandhinagar trial field-tested a 5.56 km hybrid free-space QKD and post-quantum stack, with longer links and satellite use still ahead.
Find out more here.
—
Further articles, reports, and the latest quantum computing news may be found at The Qubit Report.
Related Articles
Quantum Computing Weekly Round-Up: Week Ending October 3, 2026
Quantum computing weekly round-up time, and the week ending October 3, 2026 did not bother with a soft open. Albuquerque handed keys to a 35,000-square-foot
The Qubit Report: October 2, 2026
Immanuel Bloch shares the 2026 Wolf Prize while FeBI Technologies lands $2.2 million for a quantum iron test aimed at First Nations clinics. The same
Quantum is On in Chattanooga: Quantum in Business Showcases How Companies are Putting Quantum Technologies to Work
EPB Quantum drew more than 450 business leaders to the Quantum in Business conference in Chattanooga on October 1, 2026. The utility and IonQ used