Nat Mater. 2010 Apr;9(4):304-8. doi: 10.1038/nmat2717. Epub 2010 Mar 7.
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.
尽管光和物质具有不同的性质，但在强耦合条件下，它们可以统一起来，形成两种物质的叠加，称为 dressed states 或 polaritons。强耦合现象最初在体半导体和原子系统中得到了证明，最近在固态光学微腔中得到了实现。强耦合是从多体量子相干现象（如玻色-爱因斯坦凝聚和超流）到腔量子电动力学的物理学的一个重要组成部分。在腔量子电动力学中，Jaynes-Cummings 模型描述了单个费米子两能级系统与单个玻色光子模式的相互作用。对于光子数大于一，即所谓的量子强耦合，对于 dressed states 的阶梯状谱，预计会有显著的非谐性。对于半导体纳米结构中的光学跃迁，最近首次报道了量子强耦合的迹象。在这里，我们使用先进的相干非线性光谱学来探索一个强耦合的激子-腔系统。我们测量并模拟了它的四波混频响应，直接获得了 Jaynes-Cummings 阶梯的第一和第二梯级的相干动力学。丰富的实验证据与 Jaynes-Cummings 模型的预测相符，证明了所研究的固态系统中存在量子强耦合 regime。
