Towards Quantum Vacuum Birefringence using an X-ray Dark-field Technique at European XFEL

According to quantum field theory, the vacuum is not really "empty". For example, it can interact with strong electromagnetic fields. This extremely weak effect should also be visible in the scattering of X-ray photons in the optical field of strong laser fields - and be about two orders of magnitude stronger. Physicists call this light-by-light scattering. As part of the HIBEF collaboration at the HED experiment station of the European XFEL in Schenefeld near Hamburg, the team led by Thomas E Cowan from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is investigating whether this effect can be measured - HIBEF stands for Helmholtz International Beamline for Extreme Fields and HED for High Energy Density.