Jaynes-Cummings model: vacuum Rabi oscillations, collapse and revival
The Jaynes-Cummings model describes a two-level atom in a single-mode cavity with coupling H = g(σ₊a + σ₋a†). For a Fock state |n⟩, the vacuum Rabi frequency is Ω_n = 2g√(n+1). Starting from |e,0⟩, the atom undergoes perfect oscillations. For a coherent state |α⟩ (mean photon number n̄ = |α|²), different Fock components dephase, causing collapse; quantum revivals occur at t_rev = π|α|/g.