The government has said that a project to demonstrate long-range free-space Quantum Key Distribution (QKD) is in the planning stage with an estimated cost of ₹118 crore, as part of efforts to develop a quantum communication-based secure system for defence and strategic communications.
The update came in response to a question in the Lok Sabha on projects under implementation to develop a quantum communication-based defence system.
In a written reply, the government said that a fibre-based secure quantum communication project has already been completed and that a 200 Km fibre Quantum Key Distribution proof-of-concept link has been demonstrated.
“A Project for demonstrating fibre based secure quantum communication has been completed and Proof of Concept (POC) for 200 km fibre Quantum Key Distribution (QKD) has been successfully established,” MoS Defence Sanjay Seth said.
These earlier demonstrations form the technological foundation for the proposed long-range free-space system.
Unlike fibre-based QKD, free-space quantum communication enables secure links through open-air optical channels, making it particularly useful in locations where laying optical fibre is difficult, expensive, or operationally impractical, including mountainous terrain, remote areas and forward defence installations.
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India has already conducted experimental demonstrations to validate such technologies.
In June 2025, researchers from the Defence Research and Development Organisation (DRDO) and the Indian Institute of Technology Delhi demonstrated quantum entanglement-based free-space quantum secure communication over a distance exceeding one kilometre using a free-space optical link established on the IIT Delhi campus.
The experiment achieved a secure key rate of around 240 bits per second with a quantum bit error rate below 7 per cent, demonstrating the feasibility of real-world free-space quantum communication links.
Parallel progress has also been made in fibre-based quantum communication.
In April 2025, the Centre for Development of Telematics (C-DOT) and Sterlite Technologies Ltd. demonstrated India’s first Quantum Key Distribution transmission over a four-core multi-core optical fibre, establishing a stable link over a distance exceeding 100 Km while simultaneously transmitting high-speed classical data through other cores of the same fibre.
The demonstration showed that quantum-secure communication can operate alongside conventional data traffic within existing optical infrastructure.
Quantum Key Distribution is considered one of the most secure forms of encryption because it relies on the principles of quantum mechanics.
Any attempt to intercept or measure the quantum signal alters the quantum state of the photons, immediately revealing the presence of an eavesdropper and ensuring the integrity of the communication channel.
The proposed long-range free-space QKD project is expected to represent the next stage of development in India’s quantum communication capabilities.
Once implemented, it could strengthen efforts to build quantum-secure communication networks for defence, strategic infrastructure and other critical sectors.
