Probing High Frequency Noise with Macroscopic Resonant Tunneling
  We have developed a method for extracting the high-frequency noise spectral density of an rf-SQUID flux qubit from macroscopic resonant tunneling (MRT) rate measurements. The extracted noise spectral density is consistent with that of an ohmic environment up to frequencies ~ 4 GHz. We have also derived an expression for the MRT lineshape expected for a noise spectral density consisting of such a broadband ohmic component and an additional strongly peaked low-frequency component. This hybrid model provides an excellent fit to experimental data across a range of tunneling amplitudes and temperatures. 
T. Lanting, M.H.S. Amin, M.W. Johnson, F. Altomare, A.J. Berkley, S.   Gildert, R. Harris, J. Johansson, P. Bunyk, E. Ladizi...
cond-mat.supr-con