Vacuum Fluctuations and Spontaneous Emission in Quantum Optics

Several quantum optics problems in which spontaneous emission and/or vacuum fluctuations play an important role are discussed. These include the spontaneous decay of an atom and the damping of the field in a cavity (both in the presence of ordinary and `squeezed' vacuum), the correlated (spontaneous) emission laser or CEL, and quantum beats in V- and Λ-type three-level atoms.