Polarization quantum states of light in nonlinear distributed feedback systems; quantum nondemolition measurements of the Stokes parameters of light and atomic angular momentum

A possibility of the formation of polarization-squeezed light in the case of interaction of two orthogonally polarized modes in a spatio-periodically nonlinear Kerr-like medium is considered. It is shown that the fluctuations of the Stokes parameters of light could be less than their fluctuations in a coherent state at the output of the medium. An analysis shows that the light polarization degree is not fixed in such a nonclassical state of light. We also introduce a new nonlinear parameter of light polarization associated with the fluctuation variances of three Stokes parameters. The value of the parameter is examined for different quantum states of light. A procedure for the quantum nondemolition (QND) measurement of the Stokes parameters of light is described for the first time. We show that the precision measurement of the Stokes parameter depending on phase could be used for the QND measurement of the phase difference of two orthogonally polarized modes. The general description of the measurement procedure under study allows us to propose also a scheme for the QND measurement of angular momentum of atomic systems.