# Diagrammatic Approach to Multiphoton Scattering

## TL;DR

This paper introduces a diagrammatic Green's function method to analyze multi-photon scattering in one-dimensional quantum systems with correlated emitters, simplifying the calculation of complex many-body responses.

## Contribution

It develops a systematic, visual diagrammatic approach within the Green's function framework to efficiently compute scattering amplitudes in multi-photon, many-body quantum systems.

## Key findings

- Effective visualization of absorption and emission processes.
- Simplified calculation of nonlinear multi-photon responses.
- Application to systems with two-level emitters and Kerr nonlinear resonators.

## Abstract

We present a method to systematically study multi-photon transmission in one dimensional systems comprised of correlated quantum emitters coupled to input and output waveguides. Within the Green's function approach of the scattering matrix (S-matrix), we develop a diagrammatic technique to analytically obtain the system's scattering amplitudes while at the same time visualise all the possible absorption and emission processes. Our method helps to reduce the significant effort in finding the general response of a many-body bosonic system, particularly the nonlinear response embedded in the Green's functions. We demonstrate our proposal through physically relevant examples involving scattering of multi-photon states from two-level emitters as well as from arrays of correlated Kerr nonlinear resonators in the Bose-Hubbard model.