Extreme Lasers as Tabletop Probes of Quantum Gravity

One of the main obstacles to testing quantum gravity is that genuinely Planckian effects are expected only at energies and curvatures far beyond current experimental reach. I point out that ultrafast, high-intensity lasers, in combination with fourth-generation x-ray light sources, already allow the laboratory production of non-inertial, effectively non-Minkowski space-time regions in which quantum fields experience enormous accelerations over micron-scale distances. By the equivalence principle, these configurations are locally indistinguishable from weak, highly curved gravitational backgrounds. I emphasize a concrete, experimentally motivated observable: the broadening of x-ray Thomson scattering from electrons accelerated in the focus of an extreme laser. This broadening depends on the acceleration and the local effective metric and hence can serve as a controlled probe of quantum mechanics and, ultimately, quantum-gravity-motivated modifications in non-Minkowski space-time.