India could soon be able to use satellites for “quantum communication” within the next five years, said Professor Bhaskar Kanseri from IIT Delhi. His team recently achieved a record quantum key distribution (QKD) over one kilometer without any cables, the longest such transmission in India so far.
But getting to satellite-based quantum communication will require big, well-funded teams and startups focused on this cutting-edge tech, Prof. Kanseri explained. Quantum communication works by sharing “quantum keys” made of photons (particles of light). These keys are created using principles from quantum mechanics, which studies tiny particles like photons and atoms.
One of the most secure ways to do QKD involves something called quantum entanglement. Entangled photons are connected in a way that if one changes, the other instantly reflects that change. This means if anyone tries to spy on the communication, the people sending and receiving the information can immediately detect it and take action.
While it’s possible to create these secure keys over physical networks like fiber optic cables, doing it through “free space” (without cables) is harder but cheaper for long distances. Using satellites to connect distant points would be ideal since cables become very expensive for distances of hundreds of kilometers. However, free-space quantum communication faces challenges, especially from atmospheric issues like air turbulence and pollution. These factors cause the photon beams to scatter, leading to more errors compared to fiber optics. But with better technology and beam control, these problems can be reduced, Prof. Kanseri said.
China demonstrated satellite-based quantum communication almost a decade ago, thanks to their early start in this field. India began research more recently but is expected to catch up in about five years, especially with the support of the National Quantum Mission, which focuses on developing satellite-based long-distance quantum communication. So far, IIT Delhi’s work has been small-scale “proof of concept” projects with a handful of students. Building full satellite-based systems will be a huge effort needing lots of money and a big, skilled team. Startups working on quantum tech, guided by researchers, could help speed up turning lab ideas into real-world tech. India also needs to develop its own equipment and components to succeed, Prof. Kanseri added.
Globally, China has made big strides by using satellites 500 km above Earth to share quantum keys over 1,000 to 1,700 km distances. Other countries like Europe, Canada, and the US have done free-space QKD over 100 km on the ground. India has done shorter-range free-space quantum communication too, for example, a 300-meter atmospheric QKD link in Ahmedabad and a 50-meter link in Bangalore. Longer distance quantum communication using fiber optics has been done as well. In 2022, Prof. Kanseri’s team linked Vindhyachal and Prayagraj cities with quantum communication over underground fiber. More recently, they managed to distribute quantum keys over 100 km of telecom-grade fiber with support from India’s Defence Research and Development Organisation.
