We report on the optical preparation of coherent superpositions of exciton and biexciton states manifested in temporal nonlinear oscillations in interacting exciton gases. The effect is illustrated for atomically thin semiconductors, where the reflected light reveals these interactions in a unique way. The occurring nonlinear coherent oscillations are counteracted by incoherent excitation-induced dephasing, a phenomenon which originates from a new type of quantum interference between excitons and the two-exciton scattering continuum. To improve the experimental accessibility, we discuss different methods to control the oscillation modulation depth by modifying the mutual interplay of the exciton-biexciton superposition and excitation-induced dephasing. We find that the coherent optical response can be manipulated by the polarization degree of the exciting light field, the laser detuning, external magnetic fields, and quantum coherent feedback. The extraordinary temporal behavior and its control distinguishes the nonlinear coherent oscillations from atomic Rabi oscillations and enables their engineering based on our proposed control schemes.

中文翻译：

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激子气体中超快非线性量子叠加的光学制备和相干控制：以原子薄半导体为例

我们报告了激子和双激子态的相干叠加的光学制备，这些激子在相互作用的激子气体中表现为时间非线性振荡。说明了原子薄半导体的效果，其中反射光以独特的方式揭示了这些相互作用。发生的非线性相干振荡被不相干的励磁引起的相移所抵消，该相移是由激子和双激子散射连续体之间新型的量子干涉引起的。为了提高实验的可及性，我们讨论了通过修改激子-比激子叠加与激励引起的相移之间的相互作用来控制振荡调制深度的不同方法。我们发现相干光响应可以通过激发光场的偏振度，激光失谐，外部磁场和量子相干反馈来控制。非凡的时间行为及其控制将非线性相干振荡与原子的拉比振荡区分开来，并使其能够基于我们提出的控制方案进行工程设计。