H = ωaᵀa + ω₀σz/2 + g(aᵀσ₋ + aσ₊). For initial Fock state |n⟩, the atom oscillates at Rabi frequency Ωn = g√(n+1). Coherent states show collapse-and-revival with T_revival = 2π√⟨n⟩/g (quantum fingerprint of photon number discreteness).