Entangling free electrons and optical excitations

TL;DR

This paper proposes a method to generate pure entanglement between specific optical excitations in a cavity and free electrons by shaping the electron wave-function, overcoming previous limitations in selectivity and entanglement quality.

Contribution

It introduces a scheme to selectively entangle free electrons with targeted cavity modes by wave-function shaping, enabling higher purity entanglement in quantum systems.

Findings

Theoretical demonstration with plasmon modes in silver nanoparticles.

Application to atomic vibrations in molecules.

Potential for extending quantum interactions via electron component.

Abstract

The inelastic interaction between flying particles and optical nanocavities gives rise to entangled states in which some excitations of the latter are paired with changes in the energy or momentum of the former. In particular, entanglement of free electrons and nanocavity modes opens appealing opportunities associated with the strong interaction capabilities of the electrons. However, the degree of entanglement that is currently achievable by electron interaction with optical cavities is severely limited by the lack of external selectivity over the resulting state mixtures. Here, we propose a scheme to generate pure entanglement between designated optical excitations in a cavity and separable free-electron states. Specifically, we shape the electron wave-function profile to dramatically reduce the number of accessible cavity modes and simultaneously associate them with targeted electron scattering directions. We exemplify this concept through a theoretical description of free-electron entanglement with degenerate and nondegenerate plasmon modes in silver nanoparticles as well as atomic vibrations in an inorganic molecule. The generated entanglement can be further propagated through its electron component to extend quantum interactions beyond currently explored protocols.