Description
Light-matter interactions in time-varying materials have attracted significant interest recently, uncovering novel electromagnetic phenomena and offering enhanced functionalities of photonic devices. However, compared to the research efforts and progresses that have taken place in the classical context, the quantum aspects of this emerging subject have been less explored. Here, we study quantum light scattering at an isotropic and nondispersive material with a suddenly changing refractive index, creating a time interface. By considering the case in which a forward and a backward propagating mode exist before the temporal discontinuity, we first show that the time interface transforms the bosonic mode operators and corresponding quantum states in terms of the two-mode squeeze operator. Our analysis then focuses on quantum state engineering and photon statistics of the scattered light, which reveals and connects various quantum optical phenomena: photon-pair production and destruction, photon bunching and antibunching, vacuum generation, quantum state removal, and quantum state preservation. In general, our work provides new fundamental insights about quantized light in time-varying media and supports further investigations on more sophisticated time-interface systems, including dispersive materials and photonic time crystals, with potential applications in future quantum photonic technologies
