Single-photon scattering in a giant-molecule waveguide-QED system

TL;DR

This paper analyzes how single photons scatter in a waveguide coupled to a giant-molecule system with two coupled giant atoms, revealing how different configurations and regimes affect scattering spectra and enabling potential photon control devices.

Contribution

It provides exact analytical expressions for single-photon scattering in a giant-molecule waveguide-QED system with various configurations and regimes, highlighting controllable spectral features.

Findings

Asymmetric Fano line shapes can be achieved by tuning phase shifts.

Transmission windows are adjustable via coupling strength between atoms.

Multiple reflection peaks and dips are observed in the non-Markovian regime.

Abstract

We study the coherent single-photon scattering in a one-dimensional waveguide coupled to a giant artificial molecule consisting of two coupled giant atoms. Since each giant atom couples to the waveguide via two coupling points, the couplings of the molecule with the waveguide have three different coupling configurations: the separated-, braided-, and nested-coupling cases. We obtain the exact expressions of the single-photon transmission and reflection amplitudes with the real-space approach. It is found that the behavior of the scattering spectra depends on the phase shift between two neighboring coupling points, the coupling configuration, and the coupling between the two giant atoms. Concretely, we study the photon scattering in both the Markovian and non-Markovian regimes, in which the photon propagating time between two neighboring coupling points is neglected and considered, respectively. Under the Markovian limit, the asymmetric Fano line shapes in different coupling configurations of the giant-molecule waveguide-QED system can be obtained by choosing proper phase shift, and the transmission window can be adjusted by the coupling strength between the two giant atoms in these three coupling configurations. In particular, multiple reflection peaks and dips in these configurations are revived in the non-Markovian regime. This paper will pave the way for the study of controllable single-photon devices based on the giant-molecule waveguide-QED systems.