  The propagation of a pair of quantized fields inside a medium of three-level
atoms in $\Lambda$ configuration is analyzed. We calculate the stationary
quadrature noise spectrum of the field after propagating through the medium in
the case where the field has a general (but small) noise spectrum and the atoms
are in a coherent population trapping state and show electromagnetically
induced transparency (EIT). Although the mean values of the field remain
unaltered as the field propagates, there is an oscillatory interchange of noise
properties between the probe and pump fields. Also, as the field propagates,
there is an oscillatory creation and annihilation of correlations between the
probe and pump quadratures. We further study the field propagation of squeezed
states when there is two-photon resonance, but the field has a detuning
$\delta$ from atomic resonance. We show that the field propagation is very
sensitive to $\delta$. The propagation in this case can be explained as a
combination of a frequency dependent rotation of maximum squeezed quadrature
with an interchange of noise properties between pump and probe fields. It is
also shown that the effect of the Doppler width in a squeezed state propagation
is considerable.
