Indian quantum cybersecurity enterprise QNu Labs, in collaboration with the Bhaskaracharya National Institute for Space Applications and Geo-informatics (BISAG-N) and the Indian Institute of Technology (IIT) Gandhinagar, has completed a 5.56 km free-space Quantum Key Distribution (QKD) field trial. Conducted overnight on September 27–28, 2026, between BISAG-N and IIT Gandhinagar, the demonstration marks India’s first successful free-space QKD link at the 5 km scale.
The field trial utilized QNu Labs’ Pointing, Acquisition, and Tracking (PAT) optical system to maintain alignment over the 1550 nm quantum channel. Operating on the Differential Phase Shift (DPS)-Decoy QKD protocol, the link maintained a Quantum Bit Error Rate (QBER) below 5% and achieved a secure key rate of 230–260 bps (generating approximately one fresh 256-bit symmetric key per second). The PAT system combined gimbal-based coarse pointing (5 microradian accuracy) with fast fine steering at a 100 Hz tracking bandwidth (up to 0.1 microradian accuracy) to stabilize the optical beam against atmospheric turbulence.
| [ QNu Labs / BISAG-N Free-Space QKD Field Trial Benchmarks ] | ||
|---|---|---|
| Technical Metric / Parameter | Operational Field Benchmark | Engineering Impact & Architecture Scope |
| • Link Distance & Optics | • 5.56 km open-atmosphere optical link • 1550 nm quantum channel wavelength | • Demonstrates free-space line-of-sight QKD over multi-kilometer urban spans |
| • Key Rate & Error Bounds | • Secure key rate: 230–260 bps • Quantum Bit Error Rate (QBER): <5% | • Delivers ~1 fresh 256-bit key/sec; validates DPS-Decoy protocol under atmospheric noise |
| • PAT Optical Tracking | • Coarse pointing: 5 $\mu$rad accuracy • Fine steering: 0.1 $\mu$rad (100 Hz bandwidth) | • Mitigates thermal fluctuations and beam jitter along open-air propagation paths |
| • Hybrid Defense Integration | • Integration with BISAG-N Vedic Kavach • ETSI GS QKD 014 API delivery | • Pairs physical QKD keys with PQC software layers to maintain encryption during signal fade |
The trial demonstrated end-to-end integration with BISAG-N’s Vedic Kavach platform, a post-quantum cryptography (PQC) and quantum random number generation (QRNG)-enabled browser and web server environment. Using 256-bit keys delivered via the standard ETSI GS QKD 014 interface, test payloads were encrypted, transmitted, and decrypted across the hybrid optical-PQC layer. This dual-layer architecture ensures application security persists even if physical free-space optical channels experience temporary weather fade, establishing a technical baseline for terrestrial multi-node optical mesh networks and satellite-to-ground quantum communications.
Review the official release on the Press Information Bureau (PIB) Portal here.
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