English

Bound, antibound and resonance two-photon states in chiral waveguide QED

Quantum Physics 2026-05-22 v3

Abstract

We present a theoretical study of the two-particle spectrum ω(K)\omega(K) for the chiral waveguide QED setup of an array of two-level atoms directionally interacting with photons propagating along the waveguide. We demonstrate that for each pair center-of-mass momentum KK there exist distinct solutions with ω0\Im\omega\le 0 in the two-particle spectrum, corresponding to bound, antibound and resonance states, in addition to the continuum of scattering states. Contrary to previous studies, which showed the bound and resonance-state spectra only over a limited range of KK, the calculated spectrum is consistent across all KK values. An interesting finding is that the real part of the spectrum ω(K)\Re \omega(K) in the chiral model is gapless. The calculated dispersion law ω(K)\omega(K) provides an effective model for the bound photon pairs also in a finite-size array, manifesting the topological non-Hermitian skin effect.

Keywords

Cite

@article{arxiv.2604.20602,
  title  = {Bound, antibound and resonance two-photon states in chiral waveguide QED},
  author = {Jiaming Shi and Alexander Poddubny},
  journal= {arXiv preprint arXiv:2604.20602},
  year   = {2026}
}

Comments

v3: misprint in Eq. (8) corrected compared to v2. Code publicly available at Zenodo and Github, https://doi.org/10.5281/zenodo.19675093