Bound photonic pairs in 2D waveguide quantum electrodynamics

TL;DR

This paper predicts and analyzes two-photon bound states in a 2D waveguide lattice with atoms, revealing their properties, parameter conditions for emergence, and effects of finite system size on localization.

Contribution

It introduces the concept of bound photonic pairs in 2D waveguide QED and details their formation conditions and properties, which were not previously characterized.

Findings

Bound photon pairs form due to photon blockade and polariton dispersion.

Bound states exist only within specific parameter regimes.

Finite-size effects influence localization of these bound pairs.

Abstract

We theoretically predict the formation of two-photon bound states in a two-dimensional waveguide network hosting a lattice of two-level atoms. The properties of these bound pairs and the exclusive domains of the parameter space where they emerge due to the interplay between the on-site photon blockade and peculiar shape of polariton dispersion resulting from the long-range radiative couplings between the qubits are investigated in detail. In addition, we analyze the effect of the finite-size system on localization characteristics of these excitations.