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QNu Labs, BISAG-N and IIT Gandhinagar report completing a 5.56-kilometer free-space quantum key distribution trial on September 27–28, 2026. The link delivered a reported 230–260 bits per second with a quantum bit error rate below 5%, and a test message was encrypted, sent and decrypted through an application combining QKD keys with post-quantum cryptography.
QNu Labs, BISAG-N and IIT Gandhinagar say they completed a 5.56-kilometer free-space quantum key distribution (QKD) trial, sending quantum keys through the atmosphere and using them in a post-quantum cryptography-enabled application. Conducted on the night of September 27–28, the field test achieved a reported secure key rate of 230–260 bits per second and a quantum bit error rate below 5%; a test message was encrypted, transmitted and decrypted.
The trial connected terminals at BISAG-N and IIT Gandhinagar. QNu Labs said its Pointing, Acquisition and Tracking system maintained the 1550-nanometer optical quantum channel across the link. The system used a gimbal for coarse alignment and fine steering at a reported 100-hertz tracking bandwidth to keep the terminals aligned despite atmospheric conditions and physical movement along the path.
The organizations said they used the DPS-Decoy QKD protocol, with a quantum bit error rate below 5% and a secure key rate of 230–260 bits per second. Keys of 256 bits were delivered through the ETSI GS QKD 014 interface to BISAG-N’s Vedic Kavach browser and web server. In the reported application test, the system encrypted a message, transmitted it and successfully decrypted it at the other end.
The setup paired QKD, which distributes cryptographic keys over the optical link, with post-quantum cryptography (PQC) and quantum random number generation in the software layer. The organizations say the application was designed to remain protected if the quantum channel became temporarily unavailable. That resilience is a design description in the announcement; the report does not provide results from a test in which the channel was deliberately interrupted.
From Optical Link to Secure Application
The field trial is relevant because it reports more than a quantum signal crossing an open-air path: it connects key distribution to an application that successfully used the keys. That end-to-end demonstration addresses a practical challenge for quantum communications, where the value of a link depends on how its output is handled by real network and security systems.
The reported rate—230–260 bits per second—is modest compared with conventional data-network throughput, but QKD distributes keys rather than carrying ordinary user traffic. The groups describe generating roughly one fresh 256-bit key per second. Whether that rate is suitable for a particular deployment depends on its security design, key consumption and operating conditions, none of which are detailed in the announcement.
The combination of QKD and PQC also reflects a layered approach: QKD supplies keys over a physical channel, while the software layer uses post-quantum cryptography and quantum random numbers. The organizations say the application is designed to keep operating securely when the optical channel is unavailable. The demonstration could inform work on longer links and multi-node systems, but it does not by itself establish readiness for operational networks or satellite communications.
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How the Trial Was Set Up
The announcement describes the result as India’s first free-space QKD link at the 5-kilometer scale. That characterization comes from the organizations’ press release; the supplied material does not include an independent review or a survey of comparable trials that would verify the national-priority claim.
Free-space QKD sends quantum signals through an open optical path rather than through fiber. The trial used a 1550-nanometer channel and QNu Labs’ pointing and tracking equipment to maintain alignment between its two terminals. The partners presented the work as a field test conducted between institutional sites, not as a deployed public communications service.
The three participants contributed technology, research and test facilities. QNu Labs supplied the QKD and pointing system; BISAG-N provided the Vedic Kavach PQC-enabled browser and web server; and IIT Gandhinagar took part in the field collaboration. The trial took place September 27–28, 2026, according to the press release, and was reported on October 5.
“Quantum security will become meaningful at scale only when technologies can move beyond controlled laboratory environments and operate across real communication infrastructure.”
— Sunil Gupta, co-founder and CEO of QNu Labs
Performance Beyond This Field Test
The available announcement does not include independently verified measurements, detailed test logs or a comparison with other free-space QKD demonstrations. It also does not specify how long the link operated, how the reported key rate varied during the trial, or how atmospheric conditions affected performance. The quoted error rate and key rate should therefore be read as figures reported by the participating organizations.
Further details are also absent on the test message, application security configuration, system availability and the behavior of the PQC layer during an actual loss of the quantum channel. The claim that the link is India’s first at this scale is attributed to the press release and is not independently established by the supplied information. No deployment schedule, commercial service plan or target date for a longer link was given.
Longer Links and Network Tests
The organizations describe the 5.56-kilometer demonstration as a basis for exploring longer distances, multiple nodes and satellite-based quantum communication. Those are stated future directions, not confirmed project milestones. The announcement provides no dates, funding details or named next trial sites.
Further field testing would help establish how reliably the system performs across different weather and operating conditions, and how the hybrid application behaves when the optical channel is interrupted. Until the partners release additional results, the current evidence is limited to the reported two-site trial and its successful test-message exchange.
Key Questions
What did the three organizations demonstrate?
QNu Labs, BISAG-N and IIT Gandhinagar report a 5.56-kilometer free-space QKD link that delivered keys to a PQC-enabled browser and web server. They say a test message was encrypted, transmitted and decrypted.
When and where did the trial take place?
The organizations say the field trial took place on the night of September 27–28, 2026, between terminals at BISAG-N and IIT Gandhinagar.
What performance figures were reported?
The announcement reports a secure key rate of 230–260 bits per second and a quantum bit error rate below 5%. The figures are attributed to the participating organizations; the supplied material does not include independent verification.
Does the demonstration mean the system is ready for widespread use?
No such conclusion is established by the trial. It reports a field demonstration and an end-to-end application test, but provides no deployment schedule, long-term reliability results or evidence of a public service rollout.
What are the partners planning next?
The partners identified longer links, multi-node networks and eventual satellite-based quantum communication as areas to explore. They have not announced dates or specific milestones for those efforts.
Source: rss
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