Researchers from the Raman Research Institute (RRI) have achieved a groundbreaking milestone in India by demonstrating secure communication between a stationary source and a moving receiver using Quantum Key Distribution (QKD). This development opens up possibilities for secure quantum communication between ground and satellite-based systems in the future. The success of this demonstration is a part of the Quantum Experiments using Satellite Technology (QuEST) project, which has been a collaboration between RRI and the UR Rao Satellite Centre (URSC) since 2017. The researchers believe that these results can have significant implications for the design of secure communication channels, particularly for defense and strategic purposes, as well as for enhancing cyber security and improving the safety of online transactions.
The team, led by Prof Urbasi Sinha at the Quantum Information and Computing (QulC) lab at RRI, utilized their indigenously developed Pointing Acquisition and Tracking (PAT) system to achieve this feat. The PAT system enabled the tracking of the moving receiver, in this case, a terrestrial vehicle, by the ground-based source located a few meters away. The successful demonstration took place at RRI in early March.
This achievement builds upon the previous demonstration of QKD by the QulC lab. The earlier demonstration showcased the ability to safely share a secret key between two buildings using quantum cryptography, which encrypts messages in a way that makes them unreadable at the quantum level. Prior to that, in 2020, Sinha’s team had developed a toolkit that facilitated safe QKD between devices.
The researchers emphasized the significance of the PAT system, particularly in satellite-based long-distance quantum communication where the ground station needs to maintain a clear line of sight with the moving satellite. Although the PAT system has been widely used in satellite communications, achieving secure QKD using the PAT system between a stationary source and a mobile receiver had not been accomplished in India before. Sinha expressed excitement about this breakthrough, comparing it to the team’s previous achievement of secure quantum communication between two buildings.
The development of the PAT system by RRI researchers involved multiple phases, with each phase introducing new complexities to the experiment. Initially, they developed x-y tracking without the need for sophisticated gimbal mechanisms, which allow rotation of an object around an axis. Subsequently, they utilized the gimbal to fine-tune tracking in various degrees of freedom. To mimic satellite motion, they progressed from a homemade linear track to a homemade circular track, reflecting the advancements made in the PAT system’s development.