A quantum rotor periodically kicked by a cosine potential; Husimi phase-space distribution reveals quantum scarring and localization.
Casati et al. (1979): classical rotor shows diffusive energy growth, but quantum mechanics suppresses it — dynamical localization (Anderson localization in momentum space). Husimi Q(θ,p) = |⟨θ,p|ψ⟩|² ≥ 0, unlike the Wigner function.