# Concurrence of Two Identical Atoms in a Rectangular Waveguide: Linear Approximation with Single Excitation

## TL;DR

This paper investigates how two identical two-level atoms interact within a rectangular waveguide, focusing on their quantum entanglement dynamics using a linear approximation with a single excitation.

## Contribution

It introduces a simplified model for analyzing entanglement evolution of two TLSs in a waveguide near cutoff frequencies, considering inter-atom distance effects.

## Key findings

- Concurrence depends on inter-TLS distance and waveguide mode structure.
- Delay-differential equations describe the entanglement dynamics.
- Energy separation far from cutoff simplifies the interaction model.

## Abstract

We study two two-level systems (TLSs) interacting with a reservoir of guided modes confined in a rectangular waveguide. For the energy separation of the identical TLSs far away from the cutoff frequencies of transverse modes, the delay-differential equations are obtained with single excitation initial in the TLSs. The effects of the inter-TLS distance on the time evolution of the concurrence of the TLSs are examined.