ABSTRACT
This chapter describes a very elegant way of accounting for the symmetry of the states and the operators of systems of many identical particles and illustrates its use in a few simple calculations. It presents operators in identical particle systems that remove particles from and add particles to the system. This formal similarity is the reason the creation and annihilation operator formalism is called second quantization; one-particle wave functions appear to have become operators which create and annihilate particles, while single particle expectation values appear to have become operators for physical quantities. The Hanbury-Brown and Twiss experiment provides a simple way of observing this tendency of bosons to clump together. Basically, the experiment measures the probability of observing two photons simultaneously at different points in a beam of incoherent light. The actual measuring apparatus uses a half silvered mirror, to split the beam into some identical beams; this avoids the problem of one detector casting a shadow on the other.
