# Polarization of a probe laser beam due to nonlinear QED effects

## TL;DR

This paper investigates how nonlinear quantum electrodynamics effects, specifically photon-photon interactions, influence the polarization state of a probe laser beam in the presence of strong magnetic fields or colliding laser beams, using quantum Boltzmann equations.

## Contribution

It provides a detailed theoretical analysis of polarization evolution due to nonlinear QED effects, solving the quantum Boltzmann equation within the Euler-Heisenberg framework for various background fields.

## Key findings

- Calculated the time evolution of Stokes parameters Q, U, V.
- Predicted induced ellipticity and polarization rotation.
- Analyzed effects in both constant and time-dependent magnetic fields.

## Abstract

Nonlinear QED interactions induce different polarization properties on a given probe beam. We consider the polarization effects caused by the photon-photon interaction in laser experiments, when a laser beam propagates through a constant magnetic field or collides with another laser beam. We solve the quantum Boltzmann equation within the framework of the Euler-Heisenberg Lagrangian for both time-dependent and constant background field to explore the time evolution of the Stokes parameters Q, U, and V describing polarization. Assuming an initially linearly polarized probe laser beam, we also calculate the induced ellipticity and rotation of the polarization plane.