Single photons versus coherent state input in waveguide quantum electrodynamics: light scattering, Kerr and cross-Kerr effect

TL;DR

This paper develops a theoretical framework to compare linear and nonlinear light scattering, including Kerr effects, for Fock state and coherent state inputs in waveguide quantum electrodynamics, bridging theory and experiment.

Contribution

It introduces a comprehensive toolbox for comparing light transport and nonlinearities between Fock and coherent state inputs in waveguide QED systems.

Findings

Rules for comparing light transport properties

Generalized description of Kerr and cross-Kerr effects

Insights into nonlinearities for different input states

Abstract

While the theoretical studies in waveguide quantum electrodynamics predominate with single-photon and two-photon Fock state (photon number states) input, the experiments are primarily carried out using a faint coherent light. We create a theoretical toolbox to compare and contrast linear and nonlinear light scattering by a two-level or a three-level emitter embedded in an open waveguide carrying Fock state or coherent state inputs. We identify rules to compare light transport properties, the Kerr, and cross-Kerr nonlinearities of the medium for the two types of inputs. A generalized description of the Kerr and cross-Kerr effect for different types of inputs is formulated to compare the Kerr and cross-Kerr nonlinearity between two photons in these models.