I don't actually know if it's possible to autorotate a quadcopter. I imagine you would have very little control during the transition. Quadcopters don't fly very high anyway, so there's probably little to gain from it.
In a quadcopter the blades a small and light, so you could conceivably stop them and let them turn them in reverse as the airflow changes direction (from downwards to up through the blades). I think there would be real problem with control during the transition, and you’d need a lot of height to make it worthwhile.