India has marked a significant milestone in quantum technology by successfully demonstrating free-space quantum secure communication using quantum entanglement over a distance exceeding 1 kilometre at the IIT-Delhi campus.

This breakthrough, achieved by the Defence Research and Development Organisation (DRDO) in collaboration with IIT-Delhi’s DRDO-Industry-Academia Centre of Excellence (DIA-CoE), represents a decisive step into the quantum era and is being hailed as a “game-changer in future warfare” by Defence Minister Rajnath Singh.

The experiment utilised lasers to transmit entangled photons through open air, establishing a secure quantum key rate of approximately 240 bits per second with a quantum bit error rate below 7 percent. This entanglement-assisted quantum secure communication allows for instant detection of any eavesdropping attempts, as any interception disturbs the quantum state of the photons, alerting users to unauthorized access. The use of free-space optical links, instead of traditional fibre optic cables, makes deployment faster and more cost-effective, especially in challenging terrains and dense urban environments.

This achievement paves the way for real-time applications in quantum cybersecurity, including long-distance Quantum Key Distribution (QKD), the development of quantum networks, and the future quantum internet. Quantum communication is considered fundamentally unbreakable, offering robust security for strategic sectors such as defence, finance, and telecommunications. The technology is dual-use, supporting both civilian and national security needs.

The project, titled “Design and Development of Photonic Technologies for Free Space QKD,” was led by Professor Bhaskar Kanseri’s research group and sanctioned by the Directorate of Futuristic Technology Management (DFTM), DRDO. This demonstration builds on previous achievements, including India’s first intercity quantum communication link between Vindhyachal and Prayagraj in 2022 and a 100 km fibre-based quantum key distribution experiment in 2024.

The ongoing development of these technologies is part of a broader DRDO initiative, with 15 Centres of Excellence established at premier academic institutions across India to advance cutting-edge defence technologies. This latest milestone not only secures India’s lead in quantum technology but also sets the foundation for a nationwide quantum internet and next-generation secure communication infrastructure.

PIB