India has achieved a significant milestone in quantum-secure communications with the Defence Research and Development Organisation successfully completing military field trials of an indigenous fibre-based Quantum Key Distribution system.

The trials were conducted in collaboration with Taqbit Labs, Bengaluru, and supported by academic partners including IIT-Delhi, IISc-Bangalore, and IIT-Jodhpur.

The system was tested across a 100 km optical fibre link between Prayagraj and Vindhyachal in Uttar Pradesh, with a measured loss of 26 dB. The trials recorded a Quantum Bit Error Rate of 6 per cent and achieved a secure key rate of approximately 5 kilobits per second.

This throughput is sufficient for secure text and low-bandwidth voice encryption, while the physical layer monitoring confirmed the ability to detect eavesdropping attempts.

Earlier demonstrations had been carried out over shorter distances, including a 10 km field test in December 2020. Building on these laboratory proofs of concept and prior trials, the DRDO team and its industry partner have now successfully architected and produced a deployable system capable of securing critical networks.

The key advantage of Quantum Key Distribution lies in its reliance on the laws of quantum mechanics rather than mathematical complexity. Any attempt to intercept communication collapses the quantum state or elevates the Quantum Bit Error Rate, immediately alerting authorised users.

This makes the system immune to computational advances, including attacks from future quantum computers, and provides fundamentally unbreakable encryption.

The trials demonstrated that practical limits such as single-photon detector dead-time, clock rates, and optical channel noise can be managed effectively to maintain secure key generation in the low kilobits-per-second range. The system also tested decoy states and error correction methods to enhance reliability and throughput.

This milestone lays the foundation for building large-scale, multi-hop quantum communication networks that are indigenously designed and can seamlessly safeguard national communication infrastructure against emerging cyber threats in the quantum era. The architecture is scalable and practically secure, ensuring that India’s strategic communication networks are future-proofed against next-generation threats.

The successful trials highlight the dual-use potential of quantum communication technology. While its immediate application is in defence, the same principles can be extended to finance, telecommunications, and other critical sectors requiring secure data transmission.

By achieving this breakthrough, India has positioned itself among the leading nations advancing quantum technologies. The integration of indigenous research institutions and private industry partners underscores the strength of India’s deep-tech ecosystem and its commitment to strategic autonomy in secure communications.

Agencies