Scientists Identify India’s Best Site for Quantum Signal Transmission to Space
In a groundbreaking study, Indian scientists have identified Hanle and other areas in Ladakh as optimal locations for transmitting quantum signals into space, a significant step toward achieving secure global-scale quantum communications.
Hanle in Ladakh Emerges as Prime Site
The study, conducted by the Quantum Information and Computing (QuIC) lab at the Raman Research Institute (RRI), focused on three advanced observatory sites in India. The Indian Astronomical Observatory (IAO) in Hanle, Ladakh, emerged as the top candidate for establishing a quantum communication ground station.
Hanle’s unique environment—a cold desert with minimal atmospheric water vapour and oxygen levels—makes it ideal for reducing signal interference. The location offers natural conditions essential for uplink and downlink quantum communication, according to Professor Urbasi Sinha, head of the QuIC lab at RRI.
Quantum Communication: A Leap Beyond Traditional Methods
Unlike conventional satellite-based communications that use Mega Hertz (MHz) or Giga Hertz (GHz) frequencies, quantum communications operate at much higher Tera Hertz (THz) frequencies, often in the nanometre wavelength range. For this study, researchers worked in the 370 THz (810 nm) signal band.
To establish quantum links with Low Earth Orbit (LEO) satellites, ground stations must send beacon signals to synchronize with orbiting satellites. Once aligned, these stations facilitate secure quantum signal transmissions over long distances.
Methodology and Findings
The research utilised open-source meteorological data—temperature, humidity, and atmospheric pressure—from Hanle, Mt Abu in Rajasthan, and the Aryabhatta Institute of Observational Sciences (ARIES) in Nainital, Uttarakhand. Signal losses were evaluated for each site, with Hanle showing the lowest loss at 44 dB, followed by Mt Abu (47 dB) and Nainital (48 dB).
Lead author Satya Ranjan Behera explained that the multi-layered atmosphere presents a challenge for transmitting quantum signals, requiring minimal beam divergence and the use of small telescopes for effective signal transmission and reception.
Implications for Future Quantum Projects
India’s diverse geography, from the Himalayas to tropical regions, provides an exceptional opportunity to create a universal template for satellite-based quantum communications. This study, the first of its kind for the Indian subcontinent, offers valuable insights that could benefit global quantum satellite initiatives.
As satellite-based quantum communication progresses, the findings from this study will be instrumental in setting up ground stations and advancing secure global communication networks.