We implement a new platform to realize multimode strong coupling in cavity quantum electrodynamics. In this regime, light-matter coupling becomes larger than the free-spectral range of the cavity, and the quantum emitters... [ view full abstract ]
We implement a new platform to realize multimode strong coupling in cavity quantum electrodynamics. In this regime, light-matter coupling becomes larger than the free-spectral range of the cavity, and the quantum emitters interact with several longitudinal resonator modes simultaneously. This is qualitatively different from conventional cavity quantum electrodynamics since different cavity modes may interact via the emitters The complex non-Markovian dynamics of these systems remain to be studied and understood experimentally [1].
An earlier study observed the onset of this regime in the microwave domain [2]. Our experimental setup is based on a 30 m long fiber ring resonator (Fig.1) containing an optical nanofiber. The length of the resonator leads to a free spectral range (FSR) of 7 MHz. The 400 nm waist of the nanofiber is sufficiently thin so that a large fraction of guided light is in the form of an evanescent wave around the fiber. Due to the strong transverse confinement, the single-atom coupling is already large and the collective coupling of a few ten atoms is enough to reach a coupling in excess of the FSR. We couple cesium (Cs) atoms to the resonator, by overlapping a magneto-optical trap to the nanofiber waist.
The expected transmission spectra of a multimode cavity are shown Fig. 2,computed with a simple model where the output transmission is obtained for a moderate finesse cavity containing a variable number of atoms. In a first experiment, we plan to study the transition from single-mode splitting to multimode strong coupling by varying the number of atoms interacting with the cavity field.
After a full experimental characterization of this regime of CQED, we will employ this platform making use of the multimode interaction between light and matter. In particular, we will works towards quantum annealing based quantum information processing as was proposed in [3]. The interaction between the cavity modes may also be applied to create exotic non-classical states of light. Furthermore, the setup is well suited to study non-linear optics at the few quanta level.
[1] D. O. Krimer, M. Liertzer & S. Rotter, Route from spontaneous decay to complex multimode dynamics in cavity QED. Phys. Rev. A 89, 033820(2014)
[2] N. M. Sundaresan et al., Beyond Strong Coupling in a Multimode Cavity. Phys.Rev. X 5,021035 (2015)
[3] V. Torggler, S.Krämer & H.Ritsch, Quantum annealing with ultracold atoms in a multimode optical resonator. Phys. Rev. A 95, 32310(2016).
