Heating of trapped ions from the quantum ground state
  We have investigated motional heating of laser-cooled 9Be+ ions held in radio-frequency (Paul) traps. We have measured heating rates in a variety of traps with different geometries, electrode materials, and characteristic sizes. The results show that heating is due to electric-field noise from the trap electrodes which exerts a stochastic fluctuating force on the ion. The scaling of the heating rate with trap size is much stronger than that expected from a spatially uniform noise source on the electrodes (such as Johnson noise from external circuits), indicating that a microscopic uncorrelated noise source on the electrodes (such as fluctuating patch-potential fields) is a more likely candidate for the source of heating. 
Q. A. Turchette, D. Kielpinski, B. E. King, D. Leibfried, D. M.   Meekhof, C. J. Myatt, M. A. Rowe, C. A. Sackett, C. S. Woo...