The Sudden Death And Revival Of Entanglement In The Atom-Field System

Superposition and entanglement are two basic features that distinguish the quantum world from the classical world. While quantum entanglement is recognized as a major resource. The problem of controlling the evolution of entanglement between atoms (or qubits) that interact with the environment has received a great deal of attention in recent years. The environment may be treated as a reservoir and it is well known that the interaction of an excited atom with the reservoir leads to spontaneous emission which is one of the major sources of decoherence. In light of the experimental investigations, the spontaneous emission leads to irreversible loss of information encoded in the internal states of the system and thus is regarded as the main obstacle in practical implementations of entanglement. A deeper understanding of entanglement decoherence is also expected to lead to new insights into quantum fundamentals, particularly quantum measurement and the quantum-classical transition.We investigate the time evolution of entanglement of various entangled states of a two-qubit system exposed to either squeezed reservoirs. We show that, the sudden-death and revival of entanglement always exists in the general squeezed reservoirs.. The most surprising results is that the each entanglements of various initial states maintains at a same stationry level, shoterly after the revival of entanglement that has been destroyed.