Three interconnected themes driving ultrafast spectroscopy beyond T₂
Longitudinally and transversally shaped electron wave packets can be used to tailor quantum-coherence dynamics of quasiparticle and quantum emitters in solid-state systems. We use structured free-space light and near-field plasmonic excitations to shape the electron beams both longitudinally and transversely. For our design principles, our Maxwell-Schrödinger numerical toolbox is used.
For the experimental realisation platform, we use our ultrafast scanning electron microscope that combines ultrafast sub-50-fs light pulses with a photoemission electron gun and sample chamber of a scanning electron microscope. The combination of our theoretical and experimental endeavours provides an unprecedented understanding of electron-light-matter interactions in microscopes.
We design and fabricate electron-driven photon sources that function as internal radiation sources inside electron microscopes to perform Ramsey-type interferometry and pump-probe spectroscopy with a sub-2-fs temporal resolution and sub-1-nm spatial resolution.
Our design principles include holography schemes, metamaterial concepts, machine learning inverse design, and genetic algorithm optimisation. The enabling technology for fabricating such sources are focused ion milling, e-beam lithography, and two-photon polymerization 3D printing.
We develop correlative measurement schemes for mapping quasiparticle interaction mechanisms in solid-state-based photonic systems and quantum networks to characterise decoherence dynamics with a high temporal resolution. Electron-photon correlations and quantum optical measurements inside an electron microscope provide access to dynamics invisible to conventional optical spectroscopy.
In addition, by controlling the environment of quantum emitters and quasiparticles, we plan to tailor decoherence dynamics — yet expanding the coherent control mechanisms beyond the T₂ time scale. This work has direct implications for quantum sensitive measurement schemes for solid-state-based quantum systems, where understanding and mitigating decoherence is essential for large-scale quantum correlations and solid-state-based quantum networks.