India recently marked a milestone in its scientific journey with the successful demonstration of quantum entanglement-based secure communication over a 1-kilometre free-space link. The experiment was achieved through a collaboration among the Defence Research and Development Organisation (DRDO), industry and the Indian Institute of Technology, Delhi (IIT-D).
The project, which seeks to open avenues for secure real-time communication in defence, banking and telecommunications, was established on the IIT campus in 2023, with an expected completion date by the end of the year.
“The project was started with the aim of creating an entanglement-assisted quantum key distribution (QKD) system for a distance of up to 300 metres originally, but we increased it to more than 1 kilometre, as we thought of going beyond 300 metres inside the campus,” Bhaskar Kanseri, in charge of the I-Hub Foundation for Cobotics (IHFC) at IIT-D, said.
“Our secure key rate was 240 bits per second with a quantum bit error rate (QBER) of less than 7 per cent, but the randomness and unpredictability of those bits are more significant than the number. If we had done it for 300 metres, we would have got a higher key rate with less QBER.”
In one experiment, a pair of entangled photons was generated using a potassium-based nonlinear crystal. The invisible photons polarised horizontally or vertically — encoding binary keys by using the BBM-92 (named after three scientists in 1992) protocol — aligned in a direction using a green laser. The protocol is crucial to establishing a secret key between two locations by using quantum entanglement and to detect potential eavesdropping during a communication.
What this demonstrated was entanglement-based QKD with polarisation-entangled photons a more secure approach than the “prepare-and-measure methods”.
“Even if the source producing entangled photons is in the hands of an adversary or is compromised, thanks to quantum entanglement, the security remains intact and any attempt to eavesdrop on the system will change the quantum state of the entangled photons,” Kanseri said.
The generation of the entangled photons is highly inefficient. “Out of a million laser photons, only one pair of entangled photons is created,” Kanseri said. “But even with this limitation, we managed to generate around 70,000 photons per second suitable for transmission over 1 kilometre.”
Representational image (Photo: Shutterstock)
In 2022, IIT-D and the DRDO successfully demonstrated a QKD link between Vindhyachal and Prayagraj, two cities in Uttar Pradesh, which are more than 100 kilometres apart, using a readily available dark-fibre cable. Last year, the team successfully distributed quantum keys using entanglement over a 100-kilometre spool of telecom-grade optical fibre in another DRDO-supported project.
The technology relies on the principles of quantum physics to securely distribute keys between two parties. Earlier, a popular way of sharing a security key was through a “trusted courier”. Kanseri said that ideally, one should use a different key to send a separate message. Now, the key is generated to encrypt the message and send to the other party to decrypt it later, to ensure security.
The technology is used to establish a secure communication channel, ensuring the confidentiality of transmitted data by detecting any attempt at eavesdropping.
While this might be a significant breakthrough for India, the United States (US) and China have already achieved greater advances in quantum science. The US has invested over $500 million in quantum networking through its National Quantum Initiative Act of 2018. Multiple US government agencies are working in quantum communication through projects in entanglement, teleportation and sensor networks.
The US established around 40 kilometres of quantum network connecting the Argonne National Lab to Batavia, a city in Illinois. In 2024, the country achieved quantum teleportation over a 30-kilometre fibre-optic cable carrying conventional internet traffic. It marked a major step towards scalable and secure communication.
China has taken a different approach by prioritising Qcomm over computing, especially since Edward Snowden, the former US national security contractor, leaked classified documents on global surveillance in 2013. China extensively focused on national development through its 13th and 14th five-year plans, with over $10 billion invested in infrastructure, including the National Laboratory for Quantum Information Sciences.
China has demonstrated the longest QKD network of 1,217 kilometres using fibre optic cables, from Beijing to Shanghai. It has also launched the world’s first quantum communications satellite for secured QKD over long distances, named Micius, in 2016.
China used the satellite to establish a “quantum call” and image transmission, covering 7,600 kilometres with Austria in 2017, according to the South China Morning Post. China also claimed to have demonstrated a secure quantum link, spanning more than 11,700 kilometres, between Beijing and South Africa.
India launched the National Quantum Mission (NQM) in 2023 to work on quantum communication with an initial funding of ~6,003 crore over 2023-31. The NQM envisions developing satellite-based secure quantum communication between ground stations over a range of 2,000 kilometres within India, long-distance secure quantum communication with other countries, including an inter-city QKD, as part of the mission.
India has entered a new quantum era of secure communication, which will be a game-changer in future warfare, Defence minister Rajnath Singh has said. Under the mission, four thematic hubs have been established at the Indian Institute of Science and three IIT campuses, bringing a total of 152 researchers from 43 institutions to lead quantum research & development, increase industry collaborations, incubate startups and promote international cooperation.
US-based Quad Investors Network’s (QUIN) Quantum Centre of Excellence published a report on the quantum capabilities of the Quad countries in July last year. The report, “Quantum science and technology in the Quad nations: Landscape and opportunities,” mentioned India had 82,110 postgraduate students in quantum technology-related fields in 2020, the second-highest in the world after the European Union.
In contrast to most other countries, India has a lower retention rate, roughly 70 per cent during the transition from postgraduate education to employment, highlighting an area where the government needs to step in.
Principal scientific advisor to the government, Ajay Sood, expressed concerns at a public event in July last year. He said that India must invest considerably in creating human resources in quantum technology through higher education and training.
India’s quantum research ecosystem faces critical hurdles such as infrastructure, dependence on imported hardware and a lack of private-sector investment. This demands urgent, well-coordinated investment, robust supply chains and strategic global collaborations.
“We started 20 years late, but we won’t need another 20 years to catch up. We can learn from others’ mistakes,” Kanseri said.
As of now, there are more than 100 startups in quantum communication which develop hardware, of those, only some have been able to make progress. The NQM should balance innovation with national priorities, ensuring that critical quantum capabilities grow without diverting focus from other pressing requirements, according to experts.
While India’s quantum journey is often discussed through government missions, startups are playing a crucial role in expanding capability. “India is currently straddling both the quantum 1.0 and 2.0 phases,” Mallikarjun Karra, cofounder of QuBeats, a Bengaluru-based quantum startup, said.
The technologies developed in Quantum 1.0 phase was widely used in lasers and atomic clocks based on understanding quantum phenomena. However, phase 2.0 refers to technologies where quantum states are actively engineered and controlled — like quantum computers, secure quantum communication, and ultra-sensitive quantum sensors.
Institutions like the Indian Space Research Organisation and the DRDO have historically used phase-one quantum systems. Now, with the NQM and defence ministry initiatives like iDex, India is entering the second phase. Startups are actively working on building next-generation quantum sensors and navigation systems aimed at critical use such as GPS-independent positioning. A quantum-assured outdoor magnetically aided inertial quantum navigation system is being developed under iDex.
India will need to invest in supply chains, ease the export regulations and provide specialised training to help the research-led academic and industry ecosystems in the long run.
The quantum hardware supply chain is still nascent in India. “At present, India is heavily reliant on imports for high-end quantum components like superconducting nanowire single-photon detectors, vacuum hardware and quantum-grade lasers,” Karra said.
However, efforts to indigenise are gaining ground. “We’ve begun developing coherent light sources, vapour cells and detection modules locally.” The use of quantum navigation systems in the defence sector is essential as it helps the armed forces track location and movement accurately in GPS-denied environments. These features are especially important for submarines, long-range missiles and autonomous underwater vehicles that operate in environments where GPS signals are unavailable.
In aviation, they could serve as a resilient fallback during electronic warfare or jamming.
“We’re already in early-stage collaborations with defence research groups and naval commands,” Karra said, adding that demand was growing, especially for ruggedised prototypes suited for marine and subsea deployment.Quantum hardware such as superconducting detectors and nonlinear crystals continue to be largely imported, slowing the development of a domestic hardware supply chain.
Reena Dayal, CEO, Quantum Ecosystems and Technology Council of India, said: “Building a fully domestic, end-to-end quantum hardware supply chain is unrealistic for any country.” India is taking a strategic approach, balancing critical imports with the promotion of indigenous capabilities in the medium to long term. While the NQM is beginning to align industry, academia and government efforts, much of the policy infrastructure still needs refinement.
“There remains a need for clearer procurement frameworks, sustained funding mechanisms and coordinated test infrastructure,” Dayal said, adding that was especially true for Indian startups that faced long commercialisation timelines.
Dayal said her company provides advice on strategies and policies to support startups, education, skilling and the adoption of quantum technologies, and makes policy recommendations to the central and state governments.
Building robust navigation devices and ingenious hardware will take not only innovation but a long-term vision and investment.
 "A new feat in secure communications")
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