Huang, Guanhao

Date: Tuesday, February 27, 2024
Time: 16:00
Place: ETH Campus Hönggerberg, HPF G 6
Host: Rodrigo Benevides

Interfacing free electrons and light using photonic integrated circuits

Guanhao Huang - EPFL, Switzerland

Abstract: Quantum optics studies how photons interact with other forms of matter, the understanding of which was crucial for the development of quantum mechanics as a whole. Free-electron quantum optics studies the fundamental interaction between a flying electron and quantum optical fields. The semi-classical interaction between free electrons and an intense laser field has been well studied, but the quantum nature of light remains elusive. Coherent cathodoluminescence, by its energy-conserved nature, can reveal the quantum nature of electron-light interaction under the right measurement setting. In this talk, we discuss the theoretical basis of the quantum optical interaction between free electrons and light, as well as the experimental platform we developed using integrated photonic circuits. With a classical laser field, we observe efficient stimulated free-electron interaction with both linear and nonlinear optical fields, as well as optical spatial-temporal features not directly accessible using optical means. When the cavity is in a vacuum state, the quantum nature of electron-photon interaction is revealed in the form of coherent cathodoluminescence by analyzing the correlations of particle coincidences, thanks to complete control over the photonic device, as well as event-based electron detectors. Exploring the strong correlations between the electron-energy loss and the generated photon number, we prepare non-classical optical Fock states and observe their distinct features in the second-order correlation functions measured by an HBT setup. These observations help better understand the quantum optical effects of the free-electron-photon interaction.