Dual-comb spectroscopy of many-body correlations in rubidium vapor

We use dual-comb spectroscopy to probe many-body correlations in rubidium vapor with rapid acquisition and high sensitivity. This approach enables direct observation of collective effects that arise from dipole–dipole coupling between a small number of atoms within the ensemble, without the need for complex multidimensional techniques. By analyzing the nonlinear optical response, we resolve contributions from the single-atom double-quantum coherence and from two- and three-atom correlations. The single-atom contribution reflects independent behavior, while the two-atom signals involve coupling between atoms in ground and excited states, giving rise to a collective effect. The three-atom response shows a component where the third atom resides in a zero-quantum coherence. These measurements demonstrate that dual-comb spectroscopy can resolve few-body correlation effects and provide insight into how collective quantum behavior emerges from dipole–dipole interactions.