According to https://en.wikipedia.org/wiki/Poincar%C3%A9_recurrence_theorem#Quantum_mechanical_version the most recent paper is Schulman, L. S. (1978). "Note on the quantum recurrence theorem". Phys. Rev. A 18 (5): 2379–2380.
which assumes only discrete energy levels.
If there is scattering state, the energy level is typically continuous. My question is, in such system, does the Poincaré recurrence theorem still hold? Why?