Abstract
Coupling $N$ identical emitters to the same field mode is a well-established method to enhance light-matter interaction. However, the resulting $\sqrt{N}$ boost of the coupling strength comes at the cost of a ``linearized'' (effectively semiclassical) dynamics. Here, we instead demonstrate a new approach for enhancing the coupling constant of a single quantum emitter, while retaining the nonlinear character of the light-matter interaction. We consider a single quantum emitter with $N$ nearly degenerate transitions that are collectively coupled to the same field mode. We show that in such conditions an effective Jaynes-Cummings model emerges with a boosted coupling constant of order $\sqrt{N}$. The validity and consequences of our general conclusions are analytically demonstrated for the instructive case $N=2$. We further observe that our system can closely match the spectral line shapes and photon autocorrelation functions typical of Jaynes-Cummings physics, proving that quantum optical nonlinearities are retained. Our findings match up very well with recent broadband plasmonic nanoresonator strong-coupling experiments and will, therefore, facilitate the control and detection of single-photon nonlinearities at ambient conditions.
Highlights
Coupled light-matter systems, described by the Jaynes-Cummings (JC) model [1], are of fundamental interest in testing the quantized nature of coupled light and matter degrees of freedom in the context of cavity QED [2]
In this paper we show how the exploitation of a multilevel emitter, with N nearly degenerate excited states coupled to the same field mode, increases the √effective lightmatter coupling constant by a factor of order N. This is the same scaling found in the Dicke [15] and TC models [13] with N emitters, the crucial difference is that in our case the quantum nonlinearity of the interaction is preserved: We demonstrate this based on emission spectra and second-order photon autocorrelation functions
Our analytical and numerical results suggest that the multilevel model can provide an excellent approximation to JC physics even when these imperfections are taken into account
Summary
Coupled light-matter systems, described by the Jaynes-Cummings (JC) model [1], are of fundamental interest in testing the quantized nature of coupled light and matter degrees of freedom in the context of cavity QED [2]. In order to relax the mode volume requirements (which are currently pushing the limits of nanofabrication techniques) and obtain more robust experimental realizations, it would be of great interest to find emitter systems with increased dipole moments This would result in larger coupling constants while still allowing to harness the single-emitter quantum nonlinearity of the JCM [25,26]. Here we are interested in the special case of quasidegenerate emitters that are near resonant with the cavity, i.e., we assume the parameter regime | k| gk This approximation holds, e.g., for colloidal quantum dots coupled to plasmonic nanoresonators. In this scenario a number of qualitative observations can be made
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