An ordinary laser beam carrying quantum keys trembles at the slightest movement, like a flashlight in the hand of a running person. The drone vibrates, the rover shakes, and the code falls apart. The authors figured out how to align the polarization of light (the direction of its oscillations) on both ends of the line on the fly.
In the end, the drone and the ground rover exchanged secret keys over a distance of 100 meters, moving at a speed of 1 meter per second. The transmission rate was 70.94 kilobits per second. And over a distance of 1.2 kilometers between the drone and a station, they got 2.76 kilobits per second — for the first time, quantum communication from a drone stretched beyond a kilometer.
The drone became a flying antenna that aligns the beam itself, like a cyclist holding the handlebars over bumps. This opens the way to quantum networks in cities where the terrain is uneven and buildings block the line of sight. Airborne quantum internet is no longer science fiction.
The drone and rover exchanged keys on the move at a speed of 1 m/s: that's a brisk walking pace, at which an ordinary laser pointer would already smear its spot.
In the series 'The Expanse', ships communicate via relays, but they don't use quantum communication — here, the drone itself became a flying network node, like in stories about the quantum internet of the future.