Cavity quantum-electrodynamics with pairs in a strongly interacting Fermi gas

The last decade has seen a convergence of concepts and methods between many-body physics and quantum optics, exemplified by the use of quantum gases as simulators for many-body phenomena. Cavity QED has however been restricted to a thermal or Bosonic atoms, without the ability to control independently the atom-atom and light matter interactions.I will present the experimental realization of a quantum-degenerate, strongly interacting Fermi gas coupled to a high-finesse cavity.
I will present a study of resonant photon-pair interactions in a unitary Fermi gas, using photo-association to ultra-long range molecules. The cavity transmission spectrum close to these transitions exhibits the anti-crossing characteristic of strong light-matter coupling, signaling the onset of coherent ‘Fermion-pair-polaritons’. I will describe the dependence of the optical spectrum on interaction strength, and connect the optical spectrum of the cavity with Tan’s contact, a universal property of the many-body physics of the Fermi gas. This provides a new connection between quantum optics and strongly correlated matter opening new perspectives to monitor atomic dynamics in a non-destructive.