Emergent causality and the N-photon scattering matrix in waveguide QED

Emergent causality and the N-photon scattering matrix in waveguide QED Eduardo Sánchez-Burillo, Andrea Cadarso, Luis Martin-Moreno, Juanjo Garcia- Ripoll, David Zueco New J Phys New J. Phys. 20 013017 (2018)