Magneto-optical (Faraday) rotation is a process in which the plane of light polarization rotates as light propagates through a medium along the direction of a magnetic field. In atomic vapors where ground state atomic polarization relaxes very slowly (relaxation rates º 1 Hz), there arise ultranarrow, light-power-dependent (nonlinear) features in the magnetic field dependence of Faraday rotation. The shot-noise-limited sensitivity of a magnetometer based on nonlinear Faraday rotation can exceed 10 11 G Ô Hz, corresponding to a sensitivity of 10 6 Hz Ô Hz to Zeeman sublevel shifts. Here we discuss recent progress in magnetometry based on nonlinear optical rotation and consider the application of these methods to searches for fundamental-symmetry-violating interactions.

Recent and ongoing experiments testing various fundamental discrete symmetries are discussed, including search for parity nonconservation in dysprosium and ytterbium, investigation of possibilities of searches for parity and time-reversal invariance violation in samarium, and a test of permutation properties of photons in a two-photon transition in barium. EUGENE COMMINS AND ATOMIC TESTS OF DISCRETE SYMMETRIES Professor Eugene Commins is a pioneer in a very tough business-testing fundamental symmetries of Nature with table-top atomic physics. A typical experiment of this kind takes anywhere from 8 to 15 years (and in some cases, even longer), which is a time scale not particularly well matched to that of funding agencies, or the time expected for a graduate student to complete his or her thesis. Unfortunately, not many experiments discover something unexpected, or even set limits for "new physics" at a desired level. Nevertheless, when such a result is eventually achieved, it is often of a scientific value that is hard to overestimate. Professor Commins has succeeded in bringing several experiments of this kind to fruition, starting from the first measurement of atomic parity violation in a highly forbidden atomic transition [1, 2, 3], and culminating in the most stringent limit on the P,T-violating dipole moment of the electron (discussed in B. C. Regan's contribution elsewhere in these Proceedings). In this paper, we review some of the recent and ongoing atomic tests of fundamental symmetries carried out at Berkeley by Eugene's colleagues, former students and "grandstudents." Eugene has participated in much of this work either directly, or as an unlimited source of practical advice and theoretical expertise.