High-intensity laser facilities offer prospects for directly measuring previously unobserved processes in QED, such as vacuum birefringence, photon-photon scattering and, still some way in the future, Schwinger pair production.
Combined with nonperturbative approaches such as `time dependent basis light-front quantization',[REF][REF] which is specifically targeted at time-dependent problems in field theory, the front-form promises to provide a better understanding of QED in external fields.