Probing quantum-coherent dynamics with free electrons

TL;DR

This paper develops a quantum theory to analyze how free electrons interact with quantum emitters, revealing signatures of quantum coherence in electron energy spectra and enabling new methods for probing quantum dynamics.

Contribution

It introduces a comprehensive quantum model for free electron and quantum emitter interactions, highlighting coherence signatures detectable via electron energy spectra.

Findings

Free electrons can induce transient coherent oscillations in quantum systems.

Electron energy spectra show signatures of quantum coherence and transition frequencies.

Oscillations in the zero-loss peak reveal quantum coherence effects.

Abstract

Recent advances in time-resolved cathodoluminescence have enabled ultrafast studies of single emitters in quantum materials with femtosecond temporal resolution. Here, we develop a quantum theory modeling the dynamics of free electrons interacting with quantum emitters in arbitrary initial states. Our analysis reveals that a free electron can induce transient coherent oscillations in the populations when the system is initially prepared in a coherent superposition of its states. Moreover, the electron energy spectrum exhibits a clear signature of the quantum coherence and sensitivity to the transition frequency of the emitter. These coherence effects manifest themselves as oscillations in the zero-loss peak of the spectral energy-loss probability. Our findings pave the way for characterization of quantum-coherent dynamics of individual quantum emitters by electron-probes.