Optical-cavity mode squeezing by free electrons

TL;DR

This paper demonstrates that free electrons interacting with optical cavities can generate a variety of nonclassical light states, including squeezed states, through ponderomotive effects, revealing new quantum light manipulation methods.

Contribution

It introduces a novel mechanism where low-energy electrons induce nonclassical optical states in cavities, emphasizing the significance of $A^2$ terms in the light-matter interaction.

Findings

Electron-cavity interaction can produce squeezed and coherent states.

Signatures of $A^2$ terms are observed in the electron spectrum.

The approach offers new avenues for quantum optics and electron beam shaping.

Abstract

The generation of nonclassical light states bears a paramount importance in quantum optics and is largely relying on the interaction between intense laser pulses and nonlinear media. Recently, electron beams, such as those used in ultrafast electron microscopy to retrieve information from a specimen, have been proposed as a tool to manipulate both bright and dark confined optical excitations, inducing semiclassical states of light that range from coherent to thermal mixtures. Here, we show that the ponderomotive contribution to the electron-cavity interaction, which we argue to be significant for low-energy electrons subject to strongly confined near-fields, can actually create a more general set of optical states, including coherent and squeezed states. The post-interaction electron spectrum further reveals signatures of the nontrivial role played by $A^2$ terms in the light-matter coupling Hamiltonian, particularly when the cavity is previously excited by either chaotic or coherent illumination. Our work introduces a disruptive approach to the creation of nontrivial quantum cavity states for quantum information and optics applications, while it suggests unexplored possibilities for electron beam shaping.