Time-correlated electron and photon counting microscopy

Electron microscopy based on high-energy electrons allows nanoscopic structural imaging and nano-analysis taking advantage of secondarily generated particles, such as secondary electrons, photons, or quasi-particles. Especially for the photon emission upon electron beam excitation, so-called cathodoluminescence, the correlation between primary incident electrons and emitted photons includes information on the entire interaction process. In this work, we propose time-correlated electron and photon counting microscopy, where coincidence events of primary electrons and generated photons are counted after interaction. The electron-photon time correlation enables extracting an emitter lifetime and is applicable to both coherent and incoherent photon generation processes, demonstrating a universal lifetime measurement independent of the photon state. We also introduce a correlation factor and discuss the correlation between electrons and generated coherent photons. Through momentum selection, we observe correlation changes, indicating the effective contribution of pair correlation originating from the electron-photon entanglement based on momentum conservation. The present work is a milestone for next-generation electron microscopy utilizing quantum correlation.