DRDO & IIT Delhi Achieve Secure Free-Space Quantum Communication Over More than 1 km Distance

India has taken a major leap in the world of next-generation secure communication technology. In a significant scientific breakthrough, the Defence Research and Development Organisation (DRDO) and the Indian Institute of Technology (IIT) Delhi have successfully demonstrated quantum entanglement-based free-space quantum secure communication over a distance of more than one kilometre.

This landmark achievement was carried out through the DRDO-Industry-Academia Centre of Excellence (DIA-CoE) at IIT Delhi. Using an advanced free-space optical link set up within the IIT Delhi campus, the team achieved a secure key rate of around 240 bits per second, maintaining a very low quantum bit error rate (QBER) of less than 7% — a critical factor to ensure the reliability of quantum communication.

What is Quantum Entanglement and Why is it Special?

Quantum entanglement is a unique phenomenon where two particles, such as photons, become interconnected in such a way that the state of one instantly affects the other — no matter how far apart they are. This property is now being used to create unhackable communication channels.

In this demonstration, pairs of entangled photons were generated and sent through open space over a distance of more than one kilometre. These entangled photons carried encryption keys used for secure communication. If anyone tried to intercept or measure these particles during transmission, the act of observing them would disturb their quantum state — immediately alerting the sender and receiver about a possible eavesdropper.

Why is This Important for India?

This successful demonstration paves the way for real-time, highly secure communication systems that are practically impossible to hack, even by the most advanced computers. It has potential applications in:

• Defence and military communication

• Banking and financial transactions

• Telecommunications

• Protection of critical national infrastructure

The technology can also contribute to building long-distance Quantum Key Distribution (QKD) networks, quantum internet systems, and other futuristic cyber security frameworks.

Another advantage of this technology is that it works through free-space optical links, which means there’s no need to lay optical fiber cables — often a costly and difficult task in dense cities or challenging terrains like mountains or deserts.

The Bigger Picture

This experiment was part of a DRDO-supported project titled ‘Design and development of photonic technologies for free space QKD’, under the Directorate of Futuristic Technology Management (DFTM).

The demonstration was conducted by Prof. Bhaskar Kanseri’s research group at IIT Delhi in the presence of senior officials from DRDO and IIT Delhi.

Notably, this isn’t India’s first stride in the quantum communication field. In 2022, DRDO and IIT Delhi successfully set up the country’s first intercity quantum communication link between Vindhyachal and Prayagraj using underground optical fiber. And in 2024, the same team managed to transmit quantum keys over a 100 km spool of telecom-grade fiber in another DRDO-backed project.

These consistent achievements are being nurtured under the DRDO-Industry-Academia Centres of Excellence (DIA-CoEs) initiative, a program that partners with top academic institutions like IITs, IISc, and universities to develop cutting-edge defence technologies.

India’s Entry into the Quantum Era

Congratulating the team on this milestone, Defence Minister Rajnath Singh stated that this advancement will be a game-changer for future warfare and national cyber security. DRDO Chairman Dr. Samir V Kamat and IIT Delhi Director Prof. Rangan Banerjee also lauded the achievement, marking it as a moment that signifies India’s formal entry into a new quantum era of secure communication.

This demonstration is more than just a scientific experiment — it’s a strategic step towards securing India’s communication systems in an increasingly digital and cyber-threatened world. As India pushes ahead in quantum technologies, such breakthroughs ensure the country remains prepared for future challenges in national security, finance, and information infrastructure.