Quantum reflection of photons off spatio-temporal electromagnetic field inhomogeneities

TL;DR

This paper investigates quantum reflection of photons from complex spatio-temporal electromagnetic inhomogeneities, confirming previous estimates and exploring new effects like frequency mixing, highlighting quantum reflection as a signature of vacuum nonlinearity.

Contribution

It extends previous one-dimensional studies to more realistic spatio-temporal fields and critically assesses the validity of the locally-constant-field approximation.

Findings

Reflection rates are consistent with previous estimates.

New effects such as frequency mixing are identified.

Validity regimes of approximations are clarified.

Abstract

We reconsider the recently proposed nonlinear QED effect of quantum reflection of photons off an inhomogeneous strong-field region. We present new results for strong fields varying both in space and time. While such configurations can give rise to new effects such as frequency mixing, estimated reflection rates based on previous one-dimensional studies are corroborated. On a conceptual level, we critically re-examine the validity regime of the conventional locally-constant-field approximation and identify kinematic configurations which can be treated reliably. Our results further underline the discovery potential of quantum reflection as a new signature of the nonlinearity of the quantum vacuum.