Photon emission and absorption of a single ion coupled to an optical   fiber-cavity
  We present a light-matter interface which consists of a single $^{174}$Yb$^+$ ion coupled to an optical fiber-cavity. We observe that photons at 935 nm are mainly emitted into the cavity mode and that correlations between the polarization of the photon and the spin state of the ion are preserved despite the intrinsic coupling into a single-mode fiber. Complementary, when a faint coherent light field is injected into the cavity mode we find enhanced and polarization dependent absorption by the ion. 
M. Steiner, H. M. Meyer, J. Reichel, M. K\"ohl
quant-ph physics.atom-ph