Ph.D Thesis

Ph.D StudentReinhardt Ori
SubjectUltrafast Electron-Photon Quantum Interactions
DepartmentDepartment of Electrical and Computer Engineering
Supervisor ASSOCIATE PROF. Ido Kaminer
Full Thesis textFull thesis text - English Version


The interaction of charged particles with strong electromagnetic fields is the basis for various phenomena in both classical and quantum physics. For example, electrons can create spontaneous emission, high harmonic generation, and can be used to build free electron lasers. The interaction of electrons with light is a corner stone in fields such as condensed matter, atomic, optical and plasma physics. Specifically, for free electrons, many different electron-photon interactions have been studied during the last century such as the Cherenkov effect, Smith-Purcell effect and Compton scattering. There are various applications of such interactions. Examples include spectroscopy, building small-sized optical accelerators, and the long-lasting aspiration to create novel radiation sources in new desired wavelength regions. While most of these applications are currently modeled using classical electrodynamics, it is interesting to discuss the relevant interactions in the framework of quantum mechanics, and search for regimes in which they can be further improved.

A new platform to probe quantum free electrons and their interaction with light is the ultrafast transmission electron microscope (UTEM), in which light is introduced inside a regular transmission electron microscope, allowing us access to the electro-magnetic properties of materials. An important example for a quantum electron-photon interaction in a strong field that can be investigated inside the UTEM is "photon induced near-field electron microscopy" (PINEM). In this family of interactions, relativistic electrons interact with an induced electromagnetic field, resulting in a quantized ladder of electron energy levels. A discovery of great value in PINEM-related work is the fact that under the appropriate work assumptions, the entire interaction can be described fully analytically under some approximations. Originally, PINEM was intended for spectroscopy but since then, the PINEM theory has managed to predict and explain a plethora of other phenomena.

My PhD research contributes to the theoretical foundations of the PINEM effect. I developed more advanced theories that extend the conventional effect and can predict new kinds of interactions accessible in PINEM-like experiments. I found analytical solutions for the electron wavefunction after and during the interaction, which also lead to new conservation laws in electron-laser interactions.

My thesis includes three main papers that I published during my PhD. The first paper shows that large amounts of orbital angular momentum (OAM) can be efficiently transferred between chiral plasmons and free electrons traversing them. In my second paper, I describe how to use lasers to shape electron wavepackets, showing how to create electron energy combs, energy shifts and how to narrow the electron energy distribution. My last paper talks about the concept of encoding quantum information on free electrons in the form of qubits, and how to manipulate this information by implementing quantum gates using laser pulses.

My work on the PINEM theory has managed to explain different experiments and suggest new uses and applications. I expect that in the future this theory will be used to predict more effects and be applicable to many other systems which are quantum in nature and can benefit from it.