Letter of Intent: Towards a Vacuum Birefringence Experiment at the Helmholtz International Beamline for Extreme Fields

TL;DR

This paper discusses the potential for a groundbreaking experiment to observe vacuum birefringence, a nonlinear quantum electrodynamics effect, using advanced laser and x-ray technologies at the European XFEL facility.

Contribution

It proposes a novel experimental setup combining high-intensity lasers and x-ray polarimetry to test quantum vacuum nonlinearities for the first time.

Findings

Feasibility of detecting vacuum birefringence with current technology

Integration of high-intensity lasers with x-ray polarimetry enhances detection prospects

Refined theoretical models support the experimental design

Abstract

Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent. This fundamental tenet has remained experimentally challenging and is yet to be tested in the laboratory. A particularly distinct signature of the resulting optical activity of the quantum vacuum is vacuum birefringence. This offers an excellent opportunity for a precision test of nonlinear quantum electrodynamics in an uncharted parameter regime. Recently, the operation of the high-intensity laser ReLaX provided by the Helmholtz International Beamline for Extreme Fields (HIBEF) has been inaugurated at the High Energy Density (HED) scientific instrument of the European XFEL. We make the case that this worldwide unique combination of an x-ray free-electron laser and an ultra-intense near-infrared laser together with recent advances in high-precision x-ray polarimetry, refinements of prospective discovery scenarios, and progress in their accurate theoretical modelling have set the stage for performing an actual discovery experiment of quantum vacuum nonlinearity.