  A challenge to upcoming experiments that plan to collide a particle beam with
laser pulses of moderate intensity is how to correctly incorporate quantum
effects into simulation frameworks. Using a uniform approach, we extend the
widely-used locally constant field approximation (LCFA) to derive an improved
rate of photon-seeded pair creation (the nonlinear Breit-Wheeler process). By
benchmarking our "ULCFA" expressions with the lightfront spectrum of: i) exact
analytical results and ii) numerical integration of the QED probability for
short pulses, we show that our extended approach remains accurate at smaller
values of the intensity parameter than the standard LCFA.
