Spectroscopy of three strongly coupled flux qubits
  We have carried out spectroscopic measurements of a system of three strongly coupled four-junction flux qubits. The samples studied cover a wide range of parameters with the coupling energy between neighboring qubits varying between 0.75 GHz and 6.05 GHz. The observed complicated spectra agree well with eight-level theory. The experiments are relevant for the realization of a tunable coupling between qubits. 
A. O. Niskanen, K. Harrabi, F. Yoshihara, Y. Nakamura and J. S. Tsai