  Quantum theory of self-phase and cross-phase modulation of ultrashort light
pulses in the Kerr medium is developed with taking into account the response
time of an electronic nonlinearity. The correspondent algebra of time-dependent
Bose-operators is elaborated. It is established that the spectral region of the
pulse, where the quadrature fluctuations level is lower than the shot-noise
one, depends on the value of the nonlinear phase shift, the intensity of
another pulse, and the relaxation time of the nonlinearity. It is shown that
the frequency of the pulse spectrum at which the suppression of fluctuations is
maximum can be controlled by adjusting the other pulse intensity.
