Link Analysis of a Cubesat Based Quantum Key Distribution Platform

Sebastian Philipp Neumann, Mathieu Barthélémy, Siddarth Koduru Joshi +8 more

Chune Yang Lum, Robert Bedington, Xueliang Bai +3 more

Robert Bedington, Alexander Ling, Md. Tanvirul Islam

Progress in realising quantum computers threatens to weaken existing public key encryption infrastructure. A global quantum key distribution (QKD) network can play a role in computational attack-resistant encryption. Such a network could use a constellation of high altitude platforms such as airships and satellites as trusted nodes to facilitate QKD between any two points on the globe on demand. This requires both space-to-ground and inter-platform links. However, the prohibitive cost of traditional satellite based development limits the experimental work demonstrating relevant technologies. To accelerate progress towards a global network, we use an emerging class of shoe-box sized spacecraft known as CubeSats. We have designed a polarization entangled photon pair source that can operate on board CubeSats. The robustness and miniature form factor of our entanglement source makes it especially suitable for performing pathfinder missions that studies QKD between two high altitude platforms. The technological outcomes of such mission would be the essential building blocks for a global QKD network.

Muskan Muskan, Arindam Dutta, Subhashish Banerjee

Abstract Quantum Key Distribution (QKD) via CubeSats presents a promising pathway for secure global communication. However, realistic modeling of the satellite-to-ground optical link remains a challenge due to beam divergence, atmospheric turbulence and finite key effects. In this work, we employed an elliptical beam approximation model for the downlink channel to more accurately characterize transmittance variations compared to conventional circular beam models. This refined approach facilitates a precise estimation of finite and asymptotic key rates under realistic weather conditions, for weak coherent pulse (WCP)-based efficient BB84 and standard BB84 protocols using two decoy states in a CubeSat-based downlink scenario. Our results reveal that the efficient BB84 protocol consistently yields higher key rates, particularly under turbulent conditions, making it more suitable for practical deployment. Additionally, we analyze probability distribution of key rate (PDR) across different zenith angles demonstrating the robustness of elliptical beam modeling for CubeSat-based QKD. This study provides an improved framework for designing realistic CubeSat-based QKD systems, bridging theoretical models and experimental feasibility.

Xueliang Bai, Robert Bedington, Karthik Ilangovan +5 more

Quantum Key Distribution (QKD) is a technology that can distribute private encryption keys between two parties with strong security assurances underpinned by quantum mechanics. Entanglement-based QKD is one of the strongest forms of QKD. Performing QKD using satellites can overcome the range constraints of ground-based QKD systems imposed by atmospheric losses or attenuation in optical fibers. In 2017, satellite-based QKD has been demonstrated by the Chinese Academy of Sciences’ 630kg Micius satellite. Independently in Singapore we are developing similar, but greatly more compact QKD technologies targeted at CubeSats. Our first on-orbit demonstration of a simple quantum light source was in 2016 on board the Galassia 2U CubeSat. Next on the pad, our SpooQy-1 CubeSat is a 3U GomSpace platform built at CQT that aims to validate the space-worthiness of our next generation entangled photon light source and demonstrate a radio beacon of quantum random numbers. In future missions our miniaturized entangled photon light sources can be combined with high precision Pointing, Acquisition and Tracking System (PATS) and optical communication links to enable a global QKD network with small satellites.

Sheng‐Kai Liao, Wenqi Cai, Wei-Yue Liu +31 more