  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.
