  A time-evolution of quantum meson fields is investigated in a linear sigma
model by means of the time-dependent variational approach with a squeezed
state. The chiral condensate, which is a mean field of the quantum meson
fields, and quantum fluctuations around it are treated self-consistently in
this approach. The attention is payed to the description of the relaxation
process of the chiral condensate, where the energy stored in the mean field
configuration flows to the fluctuation modes. It is shown that the quantum
fluctuations play an important role to describe this relaxation process.
