Demonstrating Miniaturised, entangled photon-pair sources on board nano satellites to enable future QKD missions

TL;DR

This paper presents progress in developing miniaturised, entangled photon-pair sources for CubeSats, demonstrating their potential for space-based quantum key distribution through in-orbit experiments and upcoming satellite missions.

Contribution

The work introduces proof-of-principle miniaturised entangled photon sources suitable for nano-satellites, validated through space tests and integrated into satellite-to-satellite QKD mission concepts.

Findings

Photon pair sources successfully operated in orbit

High brightness entangled photon source developed for space use

QKD satellite mission concept using miniaturised sources

Abstract

We report on our progress developing highly-miniaturised, polarisation-entangled, photon pair sources for CubeSats. We have a correlated photon-pair source in orbit in the NUS Galassia 2U CubeSat. We also have an entangled photon pair source in production and a high brightness (1Mcps) entangled photon-pair source in development for our upcoming satellite missions. All our sources are proof-of-principle demonstrations that the hardware necessary for entanglement-based QKD can be miniaturised and made sufficiently robust for operation in nano-satellites. The photon pairs they produce are measured with liquid crystal-based Bell state analysers and Geiger-mode avalanche photo-diodes within the source. These space missions allow our on-the-ground radiation, thermal and vibration tests to be validated and the real-world operation and aging of the source in space to be studied. A BBM92 QKD-capable design of the source has been used in a phase A study of a satellite-to-satellite QKD demonstration mission by the University of New South Wales, Canberra. This mission study uses two 6U CubeSats in LEO and aims to demonstrate QKD over separations of increasing distances as the two CubeSats drift apart.