  A localized free particle is represented by a wave packet and its motion is
discussed in most quantum mechanics textbooks. Implicit in these discussions is
the assumption of zero temperature. We discuss how the effects of finite
temperature and squeezing can be incorporated in an elementary manner. The
results show how the introduction of simple tools and ideas can bring the
reader into contact with topics at the frontiers of research in quantum
mechanics. We discuss the standard quantum limit, which is of interest in the
measurement of small forces, and decoherence of a mixed (``Schrodinger cat'')
state, which has implications for current research in quantum computation,
entanglement, and the quantum-classical interface.
