  We review experimental work on the measurement of the quantum state of
optical fields, and the relevant theoretical background. The basic technique of
optical homodyne tomography is described with particular attention paid to the
role played by balanced homodyne detection in this process. We discuss some of
the original single-mode squeezed-state measurements as well as recent
developments including: other field states, multimode measurements, array
detection, and other new homodyne schemes. We also discuss applications of
state measurement techniques to an area of scientific and technological
importance--the ultrafast sampling of time-resolved photon statistics.
