Back-reaction effects of quantum vacuum in cavity quantum electrodynamics

We theoretically study an optical system in which the back-reaction of quantum vacuum manifests itself as a sizable suppression of the absorption by a three-level emitter embedded in an optical cavity. A theoretical model including the anti-rotating-wave terms of the light-matter interaction Hamiltonian is developed to describe the conversion of zero-point fluctuations into observable radiation, as well as the back-reaction of the quantum vacuum onto the emitter.

Figure 1

(a) Sketch of the ladder level configuration in the emitter coupled to the cavity and the optical fields driving the transitions. Right panels: total emission intensities $I_{\mathrm{cav}}$ and $I_{fe}$ as a function of the Rabi frequency ${\Omega }_{eg}$ of the drive laser (solid lines). Red dashed line in panel (b): Same curve in the vanishing emitter-cavity coupling case ${\Omega }_{\mathrm{cav}}=0$. Within the RWA, both $I_{\mathrm{cav},ge}$ would be exactly zero. The chosen parameters ${\omega }_e-{\omega }_g={\omega }_L$, ${\omega }_f-{\omega }_e={\omega }_{\mathrm{cav}}$, ${\Omega }_{\mathrm{cav}}/{\omega }_{\mathrm{cav}}=0.1$, ${\Gamma }_{eg}/{\omega }_{\mathrm{cav}}=0.01$, and ${\Gamma }_{\mathrm{cav}}={\Gamma }_{fe}={10}^{-3}{\omega }_{\mathrm{cav}}$ correspond to a strong (but not ultrastrong) coupling regime.

Figure 2

Left panels: Sketches of the dressed levels of the optically driven emitter as predicted by the Hamiltonian (2). The labels indicate the dominant contribution of each eigenstate in the weak atom-cavity coupling ${\Omega }_{\mathrm{cav}}$ limit. Right panels: spectra of the spontaneous emission on the $f\leftrightarrow e$ transition [(b) and (e)] and of the cavity emission [(c) and (f)]. Upper and lower group of panels [(a) and (c)] and [(d) and (f)] refer to the ${\Omega }_{eg}/{\omega }_{\mathrm{cav}}=0.7,2$ cases, respectively. Same system parameters as in Fig. 1.

Figure 3

Solid line: Rate of photon absorption from the drive laser as a function of its Rabi frequency ${\Omega }_{eg}$. Same system parameters as in Fig. 1. Red dashed line: same curve in the vanishing emitter-cavity coupling case ${\Omega }_{\mathrm{cav}}=0$. Blue dotted line: same curve for a two-level emitter.