Two-level atom driven on resonance — Mollow triplet and photon antibunching
A two-level atom driven resonantly scatters photons in the Mollow triplet: a central elastic peak plus two inelastic sidebands at ±Ω_R (the generalized Rabi frequency). The dressed-state picture shows avoided crossings. Second-order coherence g²(0) = 0 demonstrates perfect photon antibunching — no two photons are emitted simultaneously, a purely quantum effect (Kimble, Dagenais, Mandel, 1977).