Realization of GHZ States and the GHZ Test via Cavity QED for a Cavity   Prepared in a Superposition of Zero and One Fock States
  In this article we discuss the realization of atomic GHZ states involving three-level atoms in a cascade and in a lambda configuration and we show explicitly how to use this state to perform the GHZ test in which it is possible to decide between local realism theories and quantum mechanics. The experimental realizations proposed makes use the interaction of Rydberg atoms with a cavity prepared in a state which is a superposition of zero and one Fock states. 
E. S. Guerra