  We study the pure and thermal states of quantized scalar and tensor
perturbations in various epochs of Universe evolution. We calculate the density
matrix of non-relativistic particles in an environment of these perturbations.
We show that particle's motion can be described by a stochastic equation with a
noise coming from the cosmological environment. We investigate the squeezing of
Gaussian wave packets in different epochs and its impact upon the noise of
quantized cosmological perturbations.
