An input-output approach for giant atom scatterings beyond the dipole approximation
Abstract
A giant atom is an artificial matter configuration whose spatial scale is comparable to the wavelength of the interacting electromagnetic wave, such that the usual electric-dipole approximation is no longer valid. As a consequence, certain quasi-direct scattering channels for the electromagnetic wave can arise. Given that the well-known input-output approach can only work for the usual point scattering configuration, wherein the electric-dipole approximation is well satisfied, here we develop a modified input-output approach, wherein an additional low-Q cavity channel is introduced, to treat the electromagnetic scattering problem of a giant atom. We demonstrate that, beyond the multiple coupling-point model used widely in recent publications, the present approach can well explain the Fano-type scattering spectra observed generically and extract certain physical parameters, including the energy dissipation parameter of a two-level giant atom and its coupling strength with the scattered electromagnetic wave. Consequently, we argue that various high-performance optical quantum devices, typically the giant-atom-based optical quantum switches, can be generated by engineering the Fano-type scatterings of giant atoms.
Cite
@article{arxiv.2605.11041,
title = {An input-output approach for giant atom scatterings beyond the dipole approximation},
author = {S. R. He and S. N. Wang and Y. L. Zhang and P. H. Ouyang and L. F. Wei},
journal= {arXiv preprint arXiv:2605.11041},
year = {2026}
}