Radio-Frequency Method for Investigation of Quantum Properties of   Superconducting Structures
  We implement the impedance measurement technique (IMT) for characterization of interferometer-type superconducting qubits. In the framework of this method, the interferometer loop is inductively coupled to a high-quality tank circuit. We show that the IMT is a powerful tool to study a response of externally controlled two-level system to different types of excitations. Conclusive information about qubits is obtained from the read-out of the tank properties. 
E. Il'ichev, A.Yu. Smirnov, M. Grajcar, A. Izmalkov, D. Born, N.   Oukhanski, Th. Wagner, W. Krech, H.-G. Meyer, A.M. Zagoskin