Experimental investigation of light-matter interaction when transitioning from cavity QED to waveguide QED

Cavity quantum electrodynamics (cavity QED) is conventionally described by the Jaynes- or Tavis-Cummings model, where emitters couple to a single-mode cavity. The opposite scenario, in which an ensemble of couples single spatial mode propagating light field, waveguide QED, interact with continuum frequency modes. Here we present experiment cold atoms strongly fiber-ring resonator variable length containing optical nanofiber. By changing can tailor density modes and thus explore transition from cavity QED QED. We analyse response ensemble–cavity system after sudden switch-on resonant laser find that for progressively longer resonators, Rabi oscillations typical disappear single-pass dynamics appear. Our measurements shed on interplay between collective field dynamics.