title: Up on the Jaynes-Cummings ladder of a quantum-dot/microcavity system.
abstract: In spite of their different natures, light and matter can be unified under the strong-coupling regime, yielding superpositions of the two, referred to as dressed states or polaritons. After initially being demonstrated in bulk semiconductors and atomic systems, strong-coupling phenomena have been recently realized in solid-state optical microcavities. Strong coupling is an essential ingredient in the physics spanning from many-body quantum coherence phenomena, such as Bose-Einstein condensation and superfluidity, to cavity quantum electrodynamics. Within cavity quantum electrodynamics, the Jaynes-Cummings model describes the interaction of a single fermionic two-level system with a single bosonic photon mode. For a photon number larger than one, known as quantum strong coupling, a significant anharmonicity is predicted for the ladder-like spectrum of dressed states. For optical transitions in semiconductor nanostructures, first signatures of the quantum strong coupling were recently reported. Here we use advanced coherent nonlinear spectroscopy to explore a strongly coupled exciton-cavity system. We measure and simulate its four-wave mixing response, granting direct access to the coherent dynamics of the first and second rungs of the Jaynes-Cummings ladder. The agreement of the rich experimental evidence with the predictions of the Jaynes-Cummings model is proof of the quantum strong-coupling regime in the investigated solid-state system.
authors.forename: J
authors.initials: J
authors.lastname: Kasprzak
authors.forename: S
authors.initials: S
authors.lastname: Reitzenstein
authors.forename: E A
authors.initials: EA
authors.lastname: Muljarov
authors.forename: C
authors.initials: C
authors.lastname: Kistner
authors.forename: C
authors.initials: C
authors.lastname: Schneider
authors.forename: M
authors.initials: M
authors.lastname: Strauss
authors.forename: S
authors.initials: S
authors.lastname: Höfling
authors.forename: A
authors.initials: A
authors.lastname: Forchel
authors.forename: W
authors.initials: W
authors.lastname: Langbein