Faraday spectroscopy in an optical lattice: a continuous probe of atom dynamics

• Published in: Journal of optics. B, Quantum and semiclassical optics Vol. 5; no. 4; pp. 323 - 329
• Main Authors: Smith, Greg A, Chaudhury, Souma, Jessen, Poul S
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.08.2003; Institute of Physics
• Subjects: Atomic and molecular physics; Atomic properties and interactions with photons; Exact sciences and technology; Optical cooling of atoms; trapping; Photon interactions with atoms; Physics; Optical lattices; Spin; Quantum measure; Faraday effect; Larmor precession; Magneto-optical effects; Signal-to-noise ratio; Laser cooling; Collective process; Experimental study; Atom trapping
• ISSN: 1464-4266; 1741-3575
• DOI: 10.1088/1464-4266/5/4/301

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 measurement sensitivity and associated cost in terms of decoherence caused by the 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 back-action 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.