19_nonlinear
Continuous Weak Measurement and Nonlinear Dynamics in a Cold Spin Ensemble
Greg A. Smith1, Souma Chaudhury1, Andrew Silberfarb2, Ivan H. Deutsch2, and Poul S. Jessen1
1. Optical Sciences Center, University of Arizona, Tucson, AZ 85721
2. Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131
A weak continuous quantum measurement of an atomic spin ensemble can be implemented via Faraday rotation of an off-resonance probe beam, and may be used to create and probe nonclassical spin states and dynamics. We show that the probe light shift leads to nonlinearity in the spin dynamics and limits the useful Faraday measurement window. Removing the nonlinearity allows a non-perturbing measurement on the much longer timescale set by decoherence. The nonlinear spin Hamiltonian is of interest for studies of quantum chaos and real-time quantum state estimation.