Showcasing RRI

Quantum key distribution (QKD) is a cryptographic protocol to enable two parties to share a secure key string, which can be used in a one-time pad cryptosystem. There has been an ongoing surge of interest in implementing long-haul photonic implementation of QKD protocols. However, single photons via long optical fibres would undergo considerable transmission losses resulting in a drastic drop in the secret key rate. Hence, satellite-based QKD protocols offer an effective solution which allows QKD between local area networks using satellites as a linking node. China’s Micius satellite is at the forefront of such satellite-based QKD demonstrations where they are implementing downlink-based QKD, i.e., the entangled single photon sources are in the satellite, and the optical ground stations perform the measurement.
In the QuEST-ISRO project, we are working on an uplink-based QKD protocol where our entangled photon sources will be in the ground station, and one of the photon pairs will be routed to a low earth orbit satellite. Such an uplink-based implementation makes the entangled photon sources accessible to the experimentalists and allows them greater freedom to manipulate the source module. In my talk, I will briefly overview the project and discuss the milestones we have achieved so far.

References:
1. R. Chatterjee, K. Joarder, S. Chatterjee, B. C. Sanders, and U. Sinha, Phys. Rev. App. 14, 024036 (2020).
2. R. Chatterjee, S. Chatterjee, B. C. Sanders, and U. Sinha, Indian Patent Application No. 202141023697 (2021).
3. S. Chatterjee, K. Goswami, R. Chatterjee, U. Sinha, arXiv:2208.09124 (2022).