The ERC grant has significantly advanced our research, resulting in 41 high-impact publications in Nature, Science, Nature Photonics, and Nature Physics. We have achieved all objectives and uncovered transformative insights into free-electron light-matter interactions.
SO 1.1: Background and Prospects on the Limits of Electron-Photon Energy Conversion
Advances in quantum electrodynamics have revealed the fundamental link between emitted light coherence and electron quantum coherence, influencing radiation efficiency [Karnieli et al., 2021]. Tailoring electron wavepackets optimizes energy transfer, enhancing photon emission through quantum interference [Karnieli et al., 2021]. The integration of resonant phase-matching further strengthens electron-light coupling [Dahan et al., 2020].
Quantum electron microscopy has provided new insights into light-matter coherence regimes [Mechel et al., 2021], while ultrafast electron microscopy has enabled visualization of charge dynamics at the nanoscale, bridging classical and quantum radiation processes [Yannai et al., 2023]. These advances shape the next generation of quantum-engineered radiation platforms.
SO 1.2: Devising Novel Free-Electron Light Emission Processes
Free-electron interactions with van der Waals (vdW) materials have enabled tunable X-ray sources with spectral control through electron energy modulation and material structuring [Shentcis et al., 2020]. The scalability of vdW materials enhances imaging and photonic applications [Shi et al., 2023].
Beyond classical radiation mechanisms, quantum free-electron interactions have facilitated the generation of novel quantum light, including Schrödinger cat states, Gottesman-Kitaev-Preskill (GKP) states, and entangled photon pairs [Hayun et al., 2021]. Free electrons also mediate photon entanglement, with implications for quantum computing and error correction [Baranes et al., 2022; Baranes et al., 2023].
SO 2.1: Observing Exotic Polaritons in 2D Materials and Their Heterostructures Using the Interacting Electron as a Probe
Free electrons have proven to be powerful probes of polaritonic excitations in 2D materials. Ultrafast transmission electron microscopy (UTEM) has visualized full-wave polariton dynamics, revealing acceleration, deceleration, and wave packet splitting [Kurman et al., 2021]. Observations of 2D Cherenkov radiation have introduced new regimes of free-electron-driven interactions, enabling tunable nanoscale photonics [Adiv et al., 2023].
Additionally, free-electron interactions with photonic cavities enhance coupling strength, fostering quantum photonic applications [Wang et al., 2020]. Optical vortices in van der Waals materials provide new methods for controlling structured light-matter interactions [Kurman et al., 2023].
SO 2.2: Accessing New Phases of Matter in Materials Supporting Polaritons or Affected by Them
Free-electron quantum sensing has uncovered hybrid light-matter states at the nanoscale, exposing new quantum phase transitions [Karnieli et al., 2023]. Ultrafast electron microscopy has captured laser-driven phase transitions, illustrating electronic and phononic system restructuring [Yannai et al., 2024].
Coherently shaped free electrons refine atomic-scale coherence probing, improving our understanding of extreme material transformations [Ruimy et al., 2021]. The ability to imprint quantum photonic statistics onto free electrons enhances quantum correlation studies in light-matter interactions [Dahan et al., 2021]. Advances in magnetic near-field quantum metrology provide deeper insight into spin interactions and quantum material coherence [Mechel et al., 2021].
These advancements affirm free electrons as essential tools for accessing and manipulating quantum material phases, driving the evolution of nanoscale characterization techniques.
