Generation of an Entangled State of Two Multilevel Atoms in Cavity QED

We present a simple scheme to generate a maximally entangled state of two four-level Rydberg atoms with a nonresonant cavity by cavity-assisted collisions. By using this scheme, the maximally entangled state of two N-level (N > 4) Rydberg atoms can also be obtained. During the passage of the atoms through the cavity field, they are only virtually excited. There is no quantum information that will be transferred from the atoms to the cavity in this case.