  Drone-based quantum link has the potential to realize mobile quantum network,
and entanglement distribution has been demonstrated using one and two drones.
Here we report the first drone-based quantum key distribution (QKD), with
average secure key rate larger than 8 kHz using decoy-state BB84 protocol with
polarization coding. Compact acquisition, pointing, and tracking (APT) system
and QKD modules are developed and loaded on a home-made octocopter, within
takeoff weight of 30 kg. A robust link is established between the flying
octocopter and a ground station separated 200 meters away and real-time QKD is
performed for 400 seconds. This work shows potential of drone-based quantum
communication for the future mobile quantum networks.
