India Demonstrates First 5.56-km Free-Space Quantum Key Distribution Link

India has accomplished its first demonstration of free-space Quantum Key Distribution (QKD), over 5.56 km. This is the first milestone towards the development of the quantum-secured communication network in India. The demonstration was carried out on the night of September 27–28, 2026, to set up a quantum secured communication network between BISAG-N and IIT Gandhinagar. This achievement was a result of a collaboration between QNu Labs and BISAG-N, IIT Gandhinagar. The quantum communication network maintained the Quantum Bit Error Rate of less than 5%, which generated secure keys with a rate of 230-260 bits per second (bps).

Details of Quantum Communication Network Demonstration

The trial was conducted using QNu Labs’ Pointing, Acquisition and Tracking (PAT) system to establish and sustain the free-space optical link.

This trial delivered the following results,

• Total Distance: 5.56 km
• Communication Mode: Free-space optical
• Quantum Bit Error Rate (QBER): Below 5%
• Total secured key generation rate: 230–260 bps
• Trial dates: Night of September 27–28, 2026
• Connected locations: BISAG-N and IIT Gandhinagar
• Encryption: End-to-end encryption and decryption of test messages

The quantum keys generated have been integrated with BISAG-N’s Vedic Kavach, which has post-quantum cryptography capabilities.

Operation of the Quantum Security Architecture Using Two Layers

The system utilized the integration of QKD hardware security and post-quantum cryptography (PQC).

Armos QKD from QNu Labs was deployed over free space optical links for the creation and distribution of cryptographic keys based on quantum technologies. In software terms, BISAG-N’s Vedic Kavach offered post-quantum cryptography and quantum random number generator (QRNG).

It ensures a two-layer approach to security. According to the involved organizations, such an architecture design is intended to ensure resiliency even in case the physical layer of quantum communication becomes unavailable.

What is Quantum Key Distribution?

Quantum Key Distribution is a technique used for secure exchange of cryptographic keys based on quantum mechanics.

While conventional key distribution schemes are based mostly on computational assumptions about mathematical problems, QKD utilizes quantum properties to identify the attempts to spy on the communication link. Attempting to measure quantum information can perturb its state, which indicates the presence of possible intrusion.

Thus, QKD is seen as one of the promising technologies to protect sensitive communication in the future, when quantum computers become too powerful to break current cryptosystems.

Quantum Bit Error Rate and Key Generation

Two specific technical parameters from the trial have a special importance.

The Quantum Bit Error Rate (QBER) is an indicator showing the percentage of quantum bits with errors after their transmission and measurement. In general, the lower the QBER, the better quality of the quantum channel. The QBER remained stable at less than 5% in the course of the trial.

The system produced secure keys at 230-260 bps, i.e., 230 to 260 bits of the key were generated every second.

Relation with India’s National Quantum Mission

The recent demonstration is part of India’s larger efforts towards indigenously developed quantum technologies via the National Quantum Mission (NQM).

The National Quantum Mission was sanctioned by the Union Cabinet with a budget of ₹6,003.65 crore for eight years. The goals include the development of quantum computing, quantum communication, quantum sensing and metrology, and quantum materials and devices.

Goals of communication under the NQM include the development of inter-city QKD networks spanning up to 2,000 km and satellite quantum-secured communication between ground stations over 2,000 km within India.

India has demonstrated QKD over greater distances using optical-fibre networks. A 500-km QKD network was demonstrated in 2025 by QNu Labs, and a 2026 update highlighted 1,000-km quantum communication networks under the National Quantum Mission. This is different from the current 5.56-km free-space optical demonstration.