ABSTRACT
In this chapter, we will discuss the central topic in the current
quantum optics studies, that is, entanglement. We focus mostly on
the problem of creation of entanglement between two atoms and
address the question how one could create multi-atom entangled
states. The term entanglement, one of themost intriguing properties
of multi-particle systems, was introduced by Schro¨dinger in his
discussions of the foundations of quantum mechanics. It describes
a multi-particle system that has the astonishing property that the
results of a measurement on one particle cannot be specified
independently of the results of measurements on the other particles.
Although entangled systems can be physically separated, they can
no longer be considered as independent, even when they are very
far from one another. Entanglement is not only at the heart of
the distinction between quantum and classical mechanics, but is
now regarded to be a resource central to the development of
quantum technologies ranging from quantum information, quantum
cryptography, teleportation and quantum computation to atomic
and molecular spectroscopy. These practical implementations all
stem from the realization that we may control and manipulate
quantum systems at the level of single atoms and photons to store
information and transfer the information between distant systems
in a controlled way and with high fidelity. This field of study is
a relatively new one, and considerable research activity is taking
place at present. The most active ones are the studies of practical
schemes for creation of entanglement between trapped atoms or
ions [91, 94].
