Decoherence phenomena are pervasive in the arena of nanostructures but
perhaps even more so in the study of the fundamentals of quantum mechanics and
quantum computation. Since there has been little overlap between the studies in
both arenas, this is an attempt to bridge the gap. Topics stressed include (a)
wave packet spreading in a dissipative environment, a key element in all
arenas, (b) the definition of a quantitative measure of decoherence, (c) the
near zero and zero temperature limit, and (d) the key role played by initial
conditions: system and environment entangled at all times so that one must use
the density matrix (or Wigner distribution) for the complete system or
initially decoupled system and environment so that use of a reduced density
matrix or reduced Wigner distribution is feasible. Our approach utilizes
generalized quantum Langevin equations and Wigner distributions