# Waveguide transport mediated by strong coupling with atoms

## TL;DR

This paper studies how strong dipole-dipole interactions in a chain of quantum emitters coupled to a waveguide affect single photon scattering, revealing spectral splitting, asymmetry, and bandwidth broadening.

## Contribution

It provides analytical expressions for photon scattering in emitter chains with DDI and explores how DDI influences spectral features and bandwidth in waveguide quantum electrodynamics.

## Key findings

- DDI causes spectral splitting into two peaks.
- Fano minima can estimate DDI strength.
- DDI broadens the high-reflection bandwidth in multi-emitter chains.

## Abstract

We investigate single photon scattering properties in one-dimensional waveguide coupled to quantum emitter's chain with dipole-dipole interaction (DDI). The photon transport is extremely sensitive to the location of the evanescently coupled emitters. The analytical expressions of reflection and transmission amplitudes for the chain containing two emitters with DDI are deduced by using real-space Hamiltonian. Two cases, where the two emitters symmetrically and asymmetrically couple to the waveguide, are discussed in detail. It shows that the reflection and transmission typical spectra split into two peaks due to the DDI. The Fano minimum in the spectra can also be used to estimate the strength of the DDI. Furthermore, the DDI makes spectra strongly asymmetric and create a transmission window in the region where there was zero transmission. The scattering spectra for the chain consisting of multi-emitters are also given. Our key finding is that DDI can broaden the frequency band width for high reflection when the chain consists of many emitters.