Active Stabilization of Ion Trap Radiofrequency Potentials
  We actively stabilize the harmonic oscillation frequency of a laser-cooled atomic ion confined in a rf Paul trap by sampling and rectifying the high voltage rf applied to the trap electrodes. We are able to stabilize the 1 MHz atomic oscillation frequency to better than 10 Hz, or 10 ppm. This represents a suppression of ambient noise on the rf circuit by 34 dB. This technique could impact the sensitivity of ion trap mass spectrometry and the fidelity of quantum operations in ion trap quantum information applications. 
K. G. Johnson and J. D. Wong-Campos and A. Restelli and K. A. Landsman   and B. Neyenhuis and J. Mizrahi and C. Monroe
physics.atom-ph physics.optics quant-ph