  The increasing demand for the realization of global-scale quantum
communication services necessitates critical investigation for a practical
quantum secure communication network that relies on full-time all-location
coverage. In this direction, the non-terrestrial quantum key distribution is
expected to play an important role in providing agility, maneuverability, relay
link, on-demand network, and last-mile coverage. In this work, we have
summarized the research and development that has happened until now in the
domain of quantum communication using non-terrestrial platforms with a specific
focus on the associated challenges and the relevant models. Further, to extend
the analysis beyond the existing know-how, a hybrid model involving the
features of Vasylyev et al. model and Liorni et al. model is introduced here.
The hybrid model entails us adapting a spherical beam to an elliptic beam
approximation and effectively capturing the characteristics of transmittance in
densely humid weather conditions and at low altitudes. Further, to understand
the potential impact of the weather conditions of a region on atmospheric
attenuation, as an example the average monthly visibility of Pune city was
analyzed for the years 2021 and 2022. In addition, a simulation of a generic
model is performed using a software-defined network paradigm where quantum
teleportation is simulated between distant parties using a swarm of drones in
NetSquid.

Quantum Physics