Feasibility of quantum key distribution from high altitude platforms

This paper presents the feasibility study of deploying quantum key distribution (QKD) from high altitude platforms (HAPs), as a way of securing future communications applications and services. The paper provides a thorough review of the state of the art HAP technologies and summarises the benefits that HAPs can bring to the QKD services. A detailed link budget analysis is presented in the paper to evaluate the feasibility of delivering QKD from stratospheric HAPs flying at 20 km altitude. The results show a generous link budget under most operating conditions which brings the possibility of using diverged beams, thereby simplifying the pointing, acquisition and tracking of the optical system on the HAPs and ground, potentially widening the range of future use cases where QKD could be a viable solution.