Probing optical excitations with nanometer resolution is important for understanding their dynamics and interactions down to the atomic scale. Electron microscopes currently offer the unparalleled ability of rendering spatially resolved electron spectra with combined meV and sub-nm resolution, while the use of ultrafast optical pulses enables fs temporal resolution and exposure of the electrons to ultraintense confined optical fields. Here, we theoretically investigate fundamental aspects of the interaction of fast electrons with localized optical modes that are made possible by these advances. We use a quantum optics description of the optical field to predict that the resulting electron spectra strongly depend on the statistics of the sample excitations (bosonic or fermionic) and their population (Fock, coherent, or thermal), whose autocorrelation functions are directly retrieved from the ratios of electron gain intensities. We further explore feasible experimental scenarios to probe the quantum characteristics of the sampled excitations and their populations. In particular, we present realistic simulations for electron beams interacting with optical cavities infiltrated with optically pumped quantum emitters, which we show to undergo a varied temporal evolution in the cavity mode statistics that causes radical modifications in the transmitted electron spectra depending on pump-electron delay.

中文翻译：

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用快速电子探测量子光激发

探测具有纳米级分辨率的光激发对于了解其动力学以及直至原子尺度的相互作用都非常重要。目前，电子显微镜具有无与伦比的能力，可以结合结合meV和亚纳米分辨率来呈现空间分辨的电子光谱，而使用超快光脉冲则可以实现fs时间分辨率和电子在超强受限光场中的曝光。在这里，我们从理论上研究了快速电子与局部光学模式相互作用的基本方面，这些进展使得这些模式成为可能。我们使用光场的量子光学描述来预测所得的电子光谱在很大程度上取决于样品激发（正弦或铁离子）及其数量（福克，相干或热）的统计数据，其自相关函数可直接从电子增益强度的比率中获取。我们进一步探索可行的实验方案，以探测所采样的激发及其群的量子特征。特别是，我们提出了与电子束相互作用的现实模拟，这些电子束与通过光泵浦量子发射器渗透的光腔相互作用，这表明我们在模腔模式统计中经历了变化的时间演化，这导致了透射电子光谱的根基修改，具体取决于泵浦电子延迟。