DRDO and the Indian Institute of Technology Delhi (IIT-Delhi) successfully demonstrated Quantum Entanglement-based free-space Quantum Secure Communication over a 1 km range, marking a major breakthrough in quantum cybersecurity and secure communications, on June 16, 2025.
| Photo Credit: X/@SpokespersonMoD via PTI

Defence Research and Development Organisation (DRDO)-Industry-Academia Centre of Excellence (DIA-CoE) at IIT Delhi has demonstrated free-space quantum secure communication using quantum entanglement over a distance of more than one km via an optical link. The development is being considered a key breakthrough in the field of cybersecurity.

Defence Minister Rajnath Singh has congratulated DRDO and IIT-Delhi, describing it as a landmark achievement showcasing India’s entry into a new quantum era of secure communication, “which will be a game changer in future warfare”.

The experiment, conducted on IIT-Delhi campus, attained a secure key rate of nearly 240 bits per second with a quantum bit error rate of less than 7%. “This entanglement-assisted quantum secure communication 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,” said the Defence Ministry.

Stating that the efforts aligned with India’s broader objectives to advance quantum technologies for national development, the Ministry said under the project “Design and development of photonic technologies for free space QKD”, sanctioned by the Directorate of Futuristic Technology Management of DRDO, the demonstration was given by Prof. Bhaskar Kanseri’s research group in the presence of several dignitaries.

“Quantum entanglement-based QKD offers several significant advantages over the traditional prepare-and-measure method by enhancing both security and functionality. Even if devices are compromised or imperfect, the use of quantum entanglement ensures the security of key distribution. Any attempt to measure or intercept the entangled photons disturbs the quantum state, allowing authorised users to detect the presence of an eavesdropper,” it said.

The Ministry said quantum communication provided fundamentally unbreakable encryption, making it a dual-use technology with applications in securing data in strategic sectors such as defence, finance, and telecommunications, as well as in protecting national security-related communications. “Free-space QKD eliminates the need to lay optical fibres, which can be both disruptive and expensive, especially in challenging terrains and dense urban environments,” the Ministry said.

Earlier, India’s first intercity quantum communication link between Vindhyachal and Prayagraj in 2022, using commercial-grade underground dark optical fibre was demonstrated by DRDO scientists along with Prof. Bhaskar’s team. In 2024, the team successfully distributed quantum keys using entanglement over a 100-km spool of telecom-grade optical fibre in another DRDO-supported project.

These technologies are being developed through DIA-CoEs, 15 of which have been established at premier academic institutes like IITs, IISc, and universities.