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arXiv · 2604.20602

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

Jiaming Shi·Alexander Poddubny
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Abstract

We present a theoretical study of the two-particle spectrum $\omega(K)$ 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 $K$ there exist distinct solutions with $\Im\omega\le 0$ 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 $K$, the calculated spectrum is consistent across all $K$ values. An interesting finding is that the real part of the spectrum $\Re \omega(K)$ in the chiral model is gapless. The calculated dispersion law $\omega(K)$ provides an effective model for the bound photon pairs also in a finite-size array, manifesting the topological non-Hermitian skin effect.

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Jiaming Shi, Alexander Poddubny. 2026-04-22. Bound, antibound and resonance two-photon states in chiral waveguide QED. https://doi.org/10.1103/dhdw-m239

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