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.

We analyze the influence of noise on magnetic properties of a superconducting loop which contains three Josephson junctions. This circuit is a classical analog of a persistent current (flux) qubit. A loop supercurrent induced by external magnetic field at the presence of thermal fluctuations is calculated. In order to get connection with experiment we calculate the impedance of the low-frequency tank circuit which is inductively coupled with a loop of interest. We compare obtained results with the results in quantum mode - when the three junction loop exhibits quantum tunneling of the magnetic flux. We demonstrate that the tank-loop impedance in the classical and quantum modes have different temperature dependence and can be easily distinguished experimentally.

The detailed theory for the system of a superconducting qubit coupled to the transmission line resonator is presented. We describe the system by solving analytically and numerically the master equation for the density matrix, which includes dissipative Lindblad term. We calculate the transmission coefficient, which provides the way to probe the dressed states of the qubit. The theoretical results are related to the experiment with the intermediate coupling between the qubit and the resonator, when the coupling energy is of the same order as the qubit relaxation rate.

We study the dynamics of a qubit-resonator system, when the resonator is driven by two signals. The interaction of the qubit with the high-amplitude driving we consider in terms of the qubit dressed states. Interaction of the dressed qubit with the second probing signal can essentially change the amplitude of this signal. We calculate the transmission amplitude of the probe signal through the resonator as a function of the qubit's energy and the driving frequency detuning. The regions of increase and attenuation of the transmitted signal are calculated and demonstrated graphically. We present the influence of the signal parameters on the value of the amplification, and discuss the values of the qubit-resonator system parameters for an optimal amplification and attenuation of the weak probe signal.

We present two possible methods for the fabrication of sub-micron sized Josephson junctions, namely the shadow-evaporation technique and the cross-type technology. Their importance for the field of modern super-conducting technology is discussed. As examples we present measurement results of a two-qubit sample and a prototype of a microwave detector fabricated each by one of the described methods. We review potential applications of superconducting quantum circuits based on the developed methods.

Technological processes for the fabrication of low- and high-Tc Josephson junctions, aimed for certain appli-cations, are described. On the one hand, the integration of low-Tc superconductor digital electronics with superconducting sensor arrays enables input signal processing with quantum limited resolution at millikelvin temperatures. We describe this mixed signal superconductor technology for analogue sensor readout and signal multiplexing for operating temperatures down to 300 mK. On the other hand, by making use of modern high-Tc Josephson junction technology, sensitive magnetometers, which require a modest cooling power, can be developed. Examples of the application of the mentioned processes are shown.