Zhigang Bu, Lingang Zhang, Shiyu Liu, B.C. Shen, Ruxin Li Ruxin Li, Igor Ivanov, Liangliang Ji
Vacuum manifests itself as a nonlinear polarization medium for photons in the presence of strong fields. This hallmark prediction of quantum electrodynamics remains experimentally elusive due to the weak amplitude of light-light interaction in vacuum and the difficulty of distinguishing signals from backgrounds. Here, we propose a scheme for detecting vacuum polarization effects by colliding an ultra-intense vortex laser with an X-ray free-electron laser. We uncover a super light-by-light scattering mechanism, wherein the localized azimuthal phase of the vortex laser imparts substantial tangential momentum to scattered photons. This phase-gradient-induced momentum transfer exceeds the transverse momentum of laser-photons, allowing signal photons to be kinematically deflected out of the X-ray cone. This mechanism simultaneously achieves a high signal size and a high signal-to-noise ratio without the need for X-ray polarization filtering, and paves the way for single-shot detection of nonlinear optical phenomena in quantum vacuum with current ultra-intense laser and X-ray technologies. Driven by strong fields, vacuum manifests itself as a nonlinear polarization medium, yet this hallmark prediction of quantum electrodynamics remains experimentally elusive for 90 years. Here, the authors uncover a super light-by-light scattering effect in vacuum, and propose an experimental scheme that holds promise for single-shot detection of this vacuum polarization effect with current technologies