QNu Labs’ 5.56-km Quantum Key Link: What the Gandhinagar Trial Shows

Source note (4 October 2026): India’s Ministry of Electronics and Information Technology announced a 5.56-kilometre free-space quantum key distribution (QKD) field trial on 3 October. The trial itself took place overnight on 27–28 September between BISAG-N and IIT Gandhinagar. The figures below are the ministry’s reported results; a public, independent technical audit of this specific link has not been identified.

QNu Labs, BISAG-N and IIT Gandhinagar tested a quantum-key link through open air across 5.56 km in Gandhinagar, according to the 3 October government announcement. The release says the link kept its quantum bit error rate below 5% and produced secure keys at 230–260 bits per second. The team then used the keys with BISAG-N’s Vedic Kavach platform to encrypt and decrypt test messages. These are field-trial results, not evidence of a commercially deployed or independently certified network.

What the September field trial tested

The government release identifies QNu Labs’ Armos hardware, a pointing, acquisition and tracking system, and BISAG-N’s Vedic Kavach software as parts of the demonstration. It says the software also used post-quantum cryptography and quantum random number generation. It does not disclose a full technical paper, the precise optical components, a security proof for the implemented system, daylight performance, weather resilience or long-term uptime. Therefore those points should not be inferred from the announcement.

A key rate of 230–260 bits per second describes the reported output of key material, not the speed of the encrypted messages or ordinary internet traffic. Likewise, a reported quantum bit error rate below 5% describes one measured aspect of the trial. That number alone does not establish that a complete system is “eavesdrop-proof”. Security depends on the protocol, devices, implementation and authenticated classical communication, none of which is independently documented in enough detail here to make an absolute claim.

Why the word “first” needs care

The ministry calls this India’s first free-space QKD demonstration at the scale of 5.56 km. It is not India’s first free-space QKD experiment. ISRO reported a 300-metre free-space QKD demonstration in 2021. The new announcement describes a longer link, but it does not provide a comparative registry of every Indian experiment or a peer-reviewed basis for declaring an all-time domestic record. The careful conclusion is that the ministry reported a 5.56-km field demonstration, while earlier Indian demonstrations already existed.

What it means for deployment

Free-space QKD sends optical signals between separated sites without a fibre path. This makes the field test relevant to research on links where laying fibre is difficult. Yet the published release documents one overnight experiment. It does not establish that the system works continuously in bright sunlight, fog or rain, nor that it has passed customer acceptance, defence certification or a satellite test. A ground-level link also cannot by itself prove the performance of a ground-to-satellite connection.

QKD and post-quantum cryptography are different tools. QKD concerns the distribution of key material using quantum signals; post-quantum cryptography uses algorithms designed to resist future quantum attacks on conventional networks. The ministry says the trial combined QNu’s hardware with BISAG-N’s Vedic Kavach platform and successfully encrypted and decrypted test messages. It has not published enough detail to compare that integration with an operational national network or to claim that all future decryption risks have been removed.

What to watch next

The next meaningful evidence would include a methods paper or test report, independent repeat trials, performance across daylight and adverse weather, and a clear account of how the key service integrates with existing networks. Until then, the defensible story is a government-reported field demonstration with specific distance, error-rate and key-rate figures. Its promise should be treated as a research and engineering question, not a proven commercial capability.

Sources: MeitY/PIB announcement, 3 October 2026; ISRO’s earlier free-space QKD demonstration. Later news reports chiefly repeat the ministry’s account; they do not constitute independent measurement of the reported field metrics.

Frequently Asked Questions

What did the Gandhinagar QKD trial achieve?

According to the 3 October government announcement, the 5.56-km free-space link kept its quantum bit error rate below 5% and produced secure keys at 230–260 bits per second, which were used to encrypt and decrypt test messages.

Is this India’s first free-space QKD demonstration?

Not outright. The ministry calls it the first at the 5.56-km scale, but ISRO reported a 300-metre free-space QKD demonstration in 2021.

Does the trial prove the system is eavesdrop-proof?

No. The figures are field-trial results without a public independent audit; security depends on the protocol, devices and implementation, which have not been documented in full.