  Quantum Key Distribution (QKD) allows to share random keys between two users
with unconditional security: the key is usually generated by exchanging a
stream of photons. The long-term vision of QKD is represented by a quantum
network, implemented by fiber and free-space links involving ground and/or
satellites stations. The presence of the atmospheric turbulence represents an
obstacle for free-space quantum communications, due to the increase of optical
losses. Here we introduce a method to exploit the atmospheric turbulence as a
resource for QKD. An Adaptive Real Time Selection (ARTS) technique at the
receiver allows to take advantage of the fluctuating transmissivity of the
channel, giving rise to an increase of the secure key rate.
