Free Electron Sources and Diffraction in Time
Thesis Defense
2:00 pm –
3:00 pm
Jorgensen Hall Room: 145
Contact:
Physics Department, (402) 472-2770, paoffice@unl.edu
Eric Jones
Advisor: Herman Batelaan
ABSTRACT:
The first demonstrations of photon bunching in the experiments of Hanbury Brown and Twiss are widely considered foundational to the field of quantum optics. While the experimental results could be explained by statistical arguments, they spurred applications of quantum electrodynamics which had not been considered before then. In the following decades, the field of quantum optics flourished as light sources with high quantum degeneracy were developed. In contrast, while the matter/optics analogy was repeatedly demonstrated for free electrons, it took nearly 50 years after the Hanbury Brown and Twiss experiment before a demonstration of Fermionic antibunching in an analogous electron experiment. Part of the experimental difficulties which slowed progress toward that end can be attributed to the typically low quantum degeneracy of free-electron sources, which are commonly sharp cathode tips. As a result of this low quantum degeneracy, quantum degenerate electron sources and their applications have not been fully explored.
In my dissertation defense, I will discuss progress made in our research group toward realizing an electron source with a quantum degeneracy predicted to be several orders of magnitude greater than what is typically available. Propagation of electrons in space and time is modeled with an application of the Feynman path integral solution of the time-dependent Schroedinger’s equation. The importance of considering the appropriate time dependence will be discussed in detail as it pertains to diffraction from spatial slits. The propagation of time-dependent amplitudes, that is, amplitudes describing the conjugate variables of energy and time, is shown to be a demonstration of diffraction in time, for both a Gaussian wave packet and diffraction from a temporal slit.
The signature of quantum degeneracy, e.g., Fermionic antibunching, is predicted with the propagation of those time-dependent amplitudes, which are then used to construct two-particle probability distribution functions. These theoretical predictions, and the recent demonstration of a spin-polarized pulsed electron source, support the feasibility of performing a Hanbury Brown-Twiss experiment with our pulsed electron apparatus, as well as searching for the signature of diffraction in time.
Advisor: Herman Batelaan
ABSTRACT:
The first demonstrations of photon bunching in the experiments of Hanbury Brown and Twiss are widely considered foundational to the field of quantum optics. While the experimental results could be explained by statistical arguments, they spurred applications of quantum electrodynamics which had not been considered before then. In the following decades, the field of quantum optics flourished as light sources with high quantum degeneracy were developed. In contrast, while the matter/optics analogy was repeatedly demonstrated for free electrons, it took nearly 50 years after the Hanbury Brown and Twiss experiment before a demonstration of Fermionic antibunching in an analogous electron experiment. Part of the experimental difficulties which slowed progress toward that end can be attributed to the typically low quantum degeneracy of free-electron sources, which are commonly sharp cathode tips. As a result of this low quantum degeneracy, quantum degenerate electron sources and their applications have not been fully explored.
In my dissertation defense, I will discuss progress made in our research group toward realizing an electron source with a quantum degeneracy predicted to be several orders of magnitude greater than what is typically available. Propagation of electrons in space and time is modeled with an application of the Feynman path integral solution of the time-dependent Schroedinger’s equation. The importance of considering the appropriate time dependence will be discussed in detail as it pertains to diffraction from spatial slits. The propagation of time-dependent amplitudes, that is, amplitudes describing the conjugate variables of energy and time, is shown to be a demonstration of diffraction in time, for both a Gaussian wave packet and diffraction from a temporal slit.
The signature of quantum degeneracy, e.g., Fermionic antibunching, is predicted with the propagation of those time-dependent amplitudes, which are then used to construct two-particle probability distribution functions. These theoretical predictions, and the recent demonstration of a spin-polarized pulsed electron source, support the feasibility of performing a Hanbury Brown-Twiss experiment with our pulsed electron apparatus, as well as searching for the signature of diffraction in time.