ABSTRACT
Advances in laser cooling and trapping have made possible a new kind of microscopic atomic physics experiment in which each atom is detected individually and in which the interatomic distances are known and controlled on a sub-micron scale. This chapter shows that the triplet and singlet states represent states in which the dipole moments of the two atoms are either correlated or anticorrelated. Since the two atoms’ wave-functions are identical, so are all their physical observables, including the dipole moments. The chapter describes the theory of superradiant and subradiant spontaneous emission in sufficient detail to understand current experiments. An experiment will in general prepare a partially coherent state described by a density matrix. The chapter discusses a simple physical picture of singlet and triplet states in both wave function and density matrix approaches. It also describes a classical model of the decay rate oscillations, and also shows how the experimental signal depends on the excitation conditions.
