Discovering strong-field quantum physics using the CoReLS 4 PW laser*

At the Center for Relativistic Laser Science we have commissioned the world’s most intense laser, with a 4 PW and 1.5 PW beam. It has demonstrated an intensity of I>$10^{23} W/cm^2, the highest intensity to date. At those intensities any interaction with matter involves physics at many length and momentum scales and a combination of classical and quantum dynamics is needed to describe it. Single electrons in the plasma are quickly accelerated to energies much greater than their mass must be treated in quantum electrodynamics (QED). The collective plasma dynamics, which govern the initial conditions of the interaction, do not resolve the electron Compton wavelength and have to be treated as classical. To describe such a broad range of scales, we derive from QED a new effective quantum field theory that systematically separates the classical and quantum physics. With this tool providing systematic predictions, we can search for the uniquely strong-field effects that motivate fundamental research with high-intensity lasers. We plan to experimentally validate the theory as the first laboratory probe of quantum effects in strong classical potentials observing recoil from intense classical radiation and by exploring spontaneous pair production in nonlinear Compton scattering.