ABSTRACT
The coupling of two or more quantum mechanical states representing two different quantum mechanical systems leads to a new class of quantum mechanical states called entangled states. In this case, a two level atom, coupled to a single mode quantized electromagnetic field, results in the dressed state. The Dressed State is an example of Entangled States. This state exhibits a quantum correlation between the two entities, atom and field. The interaction energy of the atom and the quantized field can be written, in the dipolar interaction case, in the same way as in the semi classical theory. The emission of a photon by an atom creates an electromagnetic field that can act with the atom itself. An atom in the excited state, in the absence of a field, decays exponentially with time. This is Wigner Weisskopf model for spontaneous emission.
