Vacuum Rabi oscillations, collapses, and revivals
The Jaynes–Cummings model H = ωa†a + (ω₀/2)σ_z + g(a†σ⁻ + aσ⁺) describes an atom-cavity system. Starting in a coherent field state |α⟩ with n̄=|α|², the atomic inversion ⟨σ_z⟩(t) shows: (1) rapid Rabi oscillations at Ω_n = 2g√n, (2) collapse due to photon-number spread, and (3) quantum revivals at t_rev ≈ π√n̄/g, a purely quantum effect with no classical analogue.