Ayesha Reezwana

Satellite-based quantum communication has emerged as a promising solution to overcome the range limitations of ground-based systems. In this implementation, network nodes in space can connect different global ground points coherently. Building an optical ground station (OGS) is a precursor towards satellite-to-ground quantum communication that can operate in an uplink or downlink configuration.

Verifying the quality of a random number generator involves performing computationally intensive statistical tests on large data sets commonly in the range of gigabytes. Limitations on computing power can restrict an end-user's ability to perform such verification. There are also applications where the user needs to publicly demonstrate that the random bits they are using pass the statistical tests without the bits being revealed. We report the implementation of an entanglement-based protocol that allows a third party to publicly perform statistical tests without compromising the privacy of the random bits.

In this work, we present the design considerations and architecture of an optical ground station being developed on National University of Singapore campus. The primary objective of the station is to enable quantum key distribution and facilitate other free space communication protocols. The development of the optical ground station is underway and it is projected to be commissioned by 2023. We elaborate on the building blocks and design techniques of the optical ground station in Singapore that can receive i.e downlink weak quantum signals from a satellite and perform necessary analysis to generate secret keys in a quantum key distribution experiment. We emphasize on the different subsystems namely the telescope system, quantum receiver, polarization correction system, and the pointing, acquisition and tracking system. We envision our ground station to support a range of beacon wavelengths to ensure its compatibility with various similar satellite missions. The working lab-configuration of the station is able to receive and analyse state of photons around 800 nm. To achieve a global quantum network, cross-compatibility among optical ground stations and quantum satellites is crucial. To facilitate this, we have initiated a collaboration with various academic groups involved in satellite based quantum key distribution research to standardize the configuration of an optical ground station. This collaboration aspires to create cross-compatibility among multiple optical ground stations and quantum satellites to enhance the efforts of a global quantum network.