# Entanglement dynamics between two-level atoms surrounding a microtoroidal cavity and influences of initial states

## TL;DR

This paper explores how initial quantum states and atom positioning affect entanglement dynamics in atoms coupled to a microtoroidal cavity, revealing controllable entanglement phenomena like sudden death, birth, and freezing.

## Contribution

It provides a detailed theoretical analysis of entanglement behavior influenced by initial states, coupling symmetry, and scattering strength in atom-cavity systems, including three-atom configurations.

## Key findings

- Entanglement can undergo sudden death, birth, or freezing depending on initial states and system parameters.
- Entanglement generation is more sensitive to scattering strength variations than to dipole-dipole interactions.
- Similar entanglement behaviors are observed in three-atom systems even with losses.

## Abstract

We theoretically investigate how the initial state influence the entanglement dynamics between two and three two-level atoms with dipole-dipole interaction (DDI) coupled to a whispering-gallery-mode (WGM) microtoroidal cavity. Two different cases, where the two atoms are coupled symmetrically or asymmetrically to the two WGMs through evanescent fields, are discussed in detail. Considering two types of initial states between the atoms and the symmetric regime, we show that for the initial entangled state, the sudden death and birth, as well as the freezing of the entanglement, can be obtained by adjusting both the scattering strength between the modes and the DDI, differently from the initial product state. Moreover, we note that the atomic entanglement generation is more susceptible to the scattering strength variation between the modes than to the DDI. In addition, for the asymmetric regime, the entanglement generation is strongly dependent on the atomic location and the scattering strength. Similar results are obtained for the case of three atoms coupled to a microtoroidal cavity, even in the presence of losses.