Indian company QNu Labs, together with the BISAG-N institute and the Indian Institute of Technology Gandhinagar (IIT Gandhinagar), has demonstrated India’s first free-space quantum key distribution link, covering 5.56 kilometres. The test took place overnight on 27–28 September.
The technology uses quantum physics to create encryption keys that reveal any attempt at interception. Instead of optical fibre, the signals travelled through the atmosphere, thanks to a system that keeps the light beams precisely aligned between the two buildings.
The link kept an error rate below 5% and generated secure keys at 230–260 bits per second, roughly one new 256-bit key every second. The keys were combined with post-quantum cryptography software, keeping data protected even if bad weather temporarily interrupts the beam.
Those involved see the test as a step towards longer quantum networks and future quantum communication between satellites and ground stations.
