  We find a one-parameter Gaussian state for an anharmonic oscillator with
quadratic and quartic terms, which depends on the energy expectation value. For
the weak coupling constant, the Gaussian state is a squeezed state of the
vacuum state. However, for the strong coupling constant, the Gaussian state
represents a different kind of condensation of bosonic particles through a
nonlinear Bogoliubov transformation of the vacuum state.
