  In this work we investigate the effectiveness of continuous-variable (CV)
entangled states, transferred through high-loss atmospheric channels, as a
means of viable quantum key distribution (QKD) between terrestrial stations and
low-Earth orbit (LEO) satellites. In particular, we investigate the role played
by the Gaussian CV states as compared to non-Gaussian states. We find that
beam-wandering induced atmospheric losses lead to QKD performance levels that
are in general quite different from those found in fixed-attenuation channels.
For example, circumstances can be found where no QKD is viable at some fixed
loss in fiber but is viable at the same mean loss in fading channels. We also
find that, in some circumstances, the QKD relative performance of Gaussian and
non-Gaussian states can in atmospheric channels be the reverse of that found in
fixed-attenuation channels. These findings show that the nature of the
atmospheric channel can have a large impact on the QKD performance. Our results
should prove useful for emerging global quantum communications that use LEO
satellites as communication relays.
