Faraday rotation of a tightly focussed beam from a single trapped atom
  Faraday rotation of a laser field induced by a single atom is demonstrated by tightly focussing a linearly polarized laser beam onto a laser-cooled ion held in a harmonic Paul trap. The polarization rotation signal is further used to measure the phase-shift associated with electromagnetically-induced-transparency and to demonstrate read-out of the internal state on the qubit transition with a detection fidelity of 98 $\pm$ 1%. These results have direct implications for single atom magnetometery and dispersive read-out of atomic superpositions. 
G. H\'etet, L. Slodi\v{c}ka, N. R\"ock and R. Blatt
physics.atom-ph quant-ph