17_faraday
Faraday Spectroscopy in an Optical Lattice: a continuous probe of atomic dynamics
Greg A. Smith, Souma Chaudhury, and Poul S. Jessen
Optical Sciences Center, University of Arizona, Tucson, AZ 85721
The linear Faraday effect is used to implement a continuous measurement of the spin of a sample of laser cooled atoms trapped in an optical lattice. One of the optical lattice beams serves also as a probe beam, thereby allowing one to monitor the atomic dynamics in real time and with minimal perturbation. A simple theory is developed to predict the measurements sensitivity and associated cost in terms of decoherence caused by scattering of probe photons. Calculated signal-to-noise ratios in measurements of Larmor precession are found to agree with experimental data for a wide range of lattice intensity and detuning. Finally, quantum backaction is estimated by comparing the measurement sensitivity to spin projection noise, and shown to be insignificant in the current experiment. A continuous quantum measurement based on Faraday spectroscopy in optical lattices may open up new possibilities for the study of quantum feedback and classically chaotic quantum systems.