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# Coherence dynamics and quantum-to-classical crossover in an exciton-cavity system in the quantum strong coupling regime

 Kasprzak, J., Sivalertporn, K., Albert, F., Schneider, C., Hoefling, S., Kamp, M., Forchel, A., Reitzenstein, S., Muljarov, Egor A. and Langbein, Wolfgang Werner 2013. Coherence dynamics and quantum-to-classical crossover in an exciton-cavity system in the quantum strong coupling regime. New Journal of Physics 15 , 045013. 10.1088/1367-2630/15/4/045013

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## Abstract

Interaction between light and matter generates optical nonlinearities, which are particularly pronounced in the quantum strong coupling regime. When a single bosonic mode couples to a single fermionic mode, a Jaynes–Cummings (JC) ladder is formed, which we realize here using cavity photons and quantum dot excitons. We measure and model the coherent anharmonic response of this strongly coupled exciton–cavity system at resonance. Injecting two photons into the cavity, we demonstrate a $\sqrt {2}$ larger polariton splitting with respect to the vacuum Rabi splitting. This is achieved using coherent nonlinear spectroscopy, specifically four-wave mixing, where the coherence between the ground state and the first (second) rung of the JC ladder can be interrogated for positive (negative) delays. With increasing excitation intensity and thus rising average number of injected photons, we observe spectral signatures of the quantum-to-classical crossover of the strong coupling regime.

Item Type: Article Publication Published Physics and Astronomy Q Science > QC Physics Institute of Physics (IoP) and Deutsche Physikalische Gesellschaft 1367-2630 30 March 2016 04 Jun 2017 05:44 http://orca-mwe.cf.ac.uk/id/eprint/53113