SRINAGAR: India’s geographical diversity, with its vast array of terrains, may soon play a pivotal role in revolutionising global quantum communications. Researchers from the Bengaluru-based Raman Research Institute (RRI), funded by the Department of Science and Technology, have identified the Indian Astronomical Observatory (IAO) in Hanle, Ladakh, as the most suitable site for establishing secure satellite-based quantum communication links.
Hanle, situated at an altitude of 14,760 feet in the cold, arid desert of south-eastern Ladakh, offers a unique combination of geographical and atmospheric conditions. With winter temperatures plummeting to minus 25 to 30 degrees Celsius, low atmospheric water vapour, and oxygen concentrations, the site provides optimal conditions for transmitting quantum signals over long distances.
“Hanle offers all required natural settings suitable for setting up a ground station and undertaking quantum communication over long distances,” said Professor Urbasi Sinha, head of the Quantum Information and Computing (QuIC) lab at RRI.
Quantum technology uses cryptographic keys that are highly secure, allowing only authorised parties to decode transmitted information. It holds immense promise for global communications by enabling ultra-secure satellite-based transmissions through quantum key distribution (QKD). However, achieving this requires identifying locations where quantum signals can traverse Earth’s multilayered and complex atmosphere with minimal interference.
RRI scientists analysed meteorological data from three of India’s premier observatories: Hanle, Mount Abu in Rajasthan, and Nainital in Uttarakhand. Their findings, published in EPJ Quantum Technology, highlighted Hanle as the prime candidate. “India offers such a vast and diverse range of geographical terrains that this work could serve as a universal template for establishing quantum communication sites worldwide,” Sinha said.
The proposed system involves satellites in Low Earth Orbit (LEO) — orbiting at altitudes up to 500 km — using beacon signals to align with ground-based telescopes. Once aligned, quantum signals can be transmitted using specialised wavelengths. “The main signal would use 810 nm, while uplink and downlink wavelengths would be 532 nm and 1550 nm, respectively,” explained Satya Ranjan Behera, the study’s lead author.
Quantum communication requires precise technology to magnify and minimise beam divergence for effective signal transmission and reception. Small telescopes are ideal for sending these focused beams into space, where a receiver telescope collects and de-magnifies them.
While Hanle emerged as the best location, Mount Abu and Nainital were also identified as viable options, given their established research facilities and suitable atmospheric conditions.
The findings underscore India’s potential to become a global hub for quantum satellite research and development. The study not only advances India’s strides in quantum communications but also highlights the broader applicability of the research in other regions with similar geographical diversity.
As the world races toward adopting quantum technologies, India’s initiatives in Ladakh and beyond could prove transformative for global communications, enabling unparalleled levels of security and efficiency.
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