India's first free-space quantum key distribution link demonstrated over 5.56 km between BISAG-N and IIT-Gandhinagar

Key facts

• Indian scientists demonstrated India's first free-space quantum-key distribution (QKD) link over 5.56 km through open air on the night of September 27-28, connecting the Bhaskaracharya National Institute for Space Applications and Geo-informatics (BISAG-N) and IIT-Gandhinagar.
• QNu Labs from Bengaluru supplied the equipment for the demonstration.
• The team achieved a quantum bit error rate of under 5% and generated secure key information at 230-260 bits per second, which was used at BISAG-N to encrypt and decrypt messages.
• The demo also used post-quantum cryptography (PQC), which combined with QKD provides two layers of protection.
• Earlier milestones: ISRO demonstrated a QKD link over 300 m, and in 2025 IIT-Delhi with the Defence Research & Development Organisation demonstrated a QKD link through just over a kilometre of free air.
• China launched the world's first QKD satellite 'Micius' in 2016, orbiting at around 500 km, and the Jinan-1 satellite launched in 2022 performed real-time QKD with portable ground stations generating up to 1 million bits per overhead pass.
• India's National Quantum Mission targets satellite-based secure quantum communication between ground stations up to 2,000 km apart and a 2,000-km inter-city QKD network over fibre-optic cables.