Spin Squeezing and Quantum Entanglement in interaction of two excited two-level atoms with a single mode coherent radiation

In the present paper, we study the relation between spin squeezing and entanglement in two two-level atoms interacting with a single mode coherent field. We use the negativity criterion for the measurement of entanglement and obtain results considering atoms in excited states initially. We conclude that our recently reported criterion for spin squeezing is suitable for characterizing entanglement of composite systems.