Sympathetic EIT laser cooling of motional modes in an ion chain
  We use electromagnetically induced transparency (EIT) laser cooling to cool motional modes of a linear ion chain. As a demonstration, we apply EIT cooling on $^{24}Mg^+$ ions to cool the axial modes of a $^9Be^+$ - $^{24}Mg^+$ ion pair and a $^9Be^+$ - $^{24}Mg^+$ - $^{24}Mg^+$ - $^9Be^+$ ion chain, thereby sympathetically cooling the $^{9}$Be$^{+}$ ions. Compared to previous implementations of conventional Raman sideband cooling, we achieve approximately an order-of-magnitude reduction in the duration required to cool the modes to near the ground state and significant reduction in required laser intensity. 
Y. Lin, J. P. Gaebler, T. R. Tan, R. Bowler, J. D. Jost, D. Leibfried,   D. J. Wineland
physics.atom-ph quant-ph