AC Stark shift noise in QND measurement arising from quantum   fluctuations of light polarization
  In a recent letter [Auzinsh {\it{et. al.}} (physics/0403097)] we have analyzed the noise properties of an idealized atomic magnetometer that utilizes spin squeezing induced by a continuous quantum nondemolition measurement. Such a magnetometer measures spin precession of $N$ atomic spins by detecting optical rotation of far-detuned probe light. Here we consider maximally squeezed probe light, and carry out a detailed derivation of the contribution to the noise in a magnetometric measurement due to the differential AC Stark shift between Zeeman sublevels arising from quantum fluctuations of the probe polarization. 
M. Auzinsh, D. Budker, D. F. Kimball, S. M. Rochester, J. E.   Stalnaker, A. O. Sushkov, V. V. Yashchuk