Cavity quantum electrodynamics (QED) manipulates the coupling of light with matter, and allows several emitters to couple coherently with one light mode¹. However, even in a many-body system, the light–matter coupling mechanism has so far been restricted to one-body processes. Leveraging cavity QED for the quantum simulation of complex, many-body systems has thus far relied on multi-photon processes, scaling down the light–matter interaction to the low energy and slow time scales of the many-body problem^2,3,4,5. Here we report cavity QED experiments using molecular transitions in a strongly interacting Fermi gas, directly coupling cavity photons to pairs of atoms. The interplay of strong light–matter and strong interparticle interactions leads to well-resolved pair polaritons—hybrid excitations coherently mixing photons, atom pairs and molecules. The dependence of the pair-polariton spectrum on interatomic interactions is universal, independent of the transition used, demonstrating a direct mapping between pair correlations in the ground state and the optical spectrum. This represents a magnification of many-body effects by two orders of magnitude in energy. In the dispersive regime, it enables fast, minimally destructive measurements of pair correlations, and opens the way to their measurement at the quantum limit and their coherent manipulation using dynamical, quantized optical fields.

腔量子电动力学 (QED) 操纵光与物质的耦合，并允许多个发射器与一种光模式¹相干耦合。然而，即使在多体系统中，光-物质耦合机制迄今为止也仅限于单体过程。迄今为止，利用腔 QED 对复杂的多体系统进行量子模拟依赖于多光子过程，将光物质相互作用缩小到多体问题的低能量和慢时间尺度^{2,3,4 ,5}. 在这里，我们报告了使用强相互作用费米气体中的分子跃迁的腔 QED 实验，将腔光子直接耦合到原子对。强光-物质和强粒子间相互作用的相互作用导致了很好分辨的极化激元——混合激发，相干混合光子、原子对和分子。对极化子光谱对原子间相互作用的依赖性是普遍的，与所使用的跃迁无关，证明了基态中的对相关性与光谱之间的直接映射。这表示多体效应的能量放大了两个数量级。在色散状态下，它可以对配对相关性进行快速、破坏性最小的测量，