Single flux quantum logic (SFQ) circuits, in which a flux quantum is used as an information carrier, have the possibility for opening the door to a new digital system operated at over 100 GHz clock frequency at extremely low power dissipations. Recently, much progress in basic technologies for designing SFQ circuits and operating circuits with high speeds has been made. With advances in these designing tools, large scale circuits including more than several thousand junctions can be easily operated with the clock frequency of more than several tens of GHz. Network devices are possible applications of SFQ logic circuits because of their high through-put nature and the low power dissipation of the SFQ logic. In this paper, recent developments of SFQ circuit technology and applications of this technology will be reviewed.

The development of MgB₂ tapes and the recent metallic superconductors was reviewed. MgB₂ tapes and wires are developed by the so-called powder-in-tube method. However, their critical current densities, Jc, are still below the practical level. Research and development such as introduction of pinning centers is required for the Jc enhancement. Improvement of practical superconductors, Nb-Ti and Nb₃Sn, is now in progress for realizing new applications such as Large Hadron Collider, high-field NMR system, ITER magnet and cryocooler-cooled magnet. Nb₃Al has gained interest because of its high mechanical tolerance. Recently, Nb₃Al tapes and wires with excellent high field performance were developed by the application of rapid heating, quenching and transformation method.

High-temperature superconductor (HTS) filters can realize both very steep skirt at the band edge and very high isolation at the stop band. The number of resonators of HTS filters can be increased without increasing insertion loss, because of their high unloaded quality factors. By applying HTS filters to the receiver front-end of the mobile telecommunication base station, the undesired signal emitted by other telecommunication systems can be sufficiently attenuated. This means that the guard band can be reduced. Therefore the increases of the frequency utilization and the capacity of the communication system are expected. In this paper, the HTS filter and filter subsystem for the receiver front-end of the mobile telecommunication base station are outlined.

Magnesium diboride (MgB₂) has recently been identified as a superconductor with T_c = 39 K, which is the highest Tc among intermetallic compounds, and has attracted great interest from the viewpoint of potential superconducting electronics applications. In this report, we present low-temperature deposition of MgB₂ thin films and fabrication of Josephson tunnel junctions. MgB₂ thin films were deposited by using a carrousel-type sputtering system without a high-temperature post annealing process. The films had T_c of 28 K at substrate temperature of 252°C and a smooth surface. We also fabricated MgB₂/AlN/NbN tunnel junctions. The junctions have good quasiparticle and Josephson current characteristics.

The clarification of the electromagnetic behavior within high-temperature superconducting (HTS) bulk is very important in order to realize its applications such as to motors, the magnetic levitation system, and bulk magnets. This paper presents the results of a comprehensive study of electromagnetic characteristics of HTS bulk by experiments and numerical simulations based on finite element analyses. We have constructed a magnetic shielding-type superconducting fault current limiter, a two-dimensional magnetic levitating transporter, an active-maglev system composed of a YBCO disk and multiple electromagnets, and a linear actuator with YBCO bulk for secondary (moving part) as model devices to clarify the characteristics of HTS bulk in a realistic operational environment of electrical machines.

Quantum computers have a novel architecture that achieves extremely fast computation. The basic element of a quantum computer is a quantum bit (qubit), and qubits have been physically implemented in a variety of systems. Recently, one qubit operation in a superconducting flux qubit was demonstrated experimentally. However, in that case the qubit states were distinguished by averaging the readout results. We successfully read out flux-qubit states by means of a single-shot measurement, which is important in terms of performing efficient quantum computation. In this paper, we report our experimental results for flux qubits and the significance of the single shot measurement.

This article explains models and methods used for simulating the ion implantation process in ULSI process simulation. The Monte Carlo simulation method is the focus of this study. To obtain reasonable simulation results, not only silicon crystal structure but also its thermal vibration and damaging process must be taken into account. On the other hand, the electronic stopping model and the binary collision approximation in the low energy range have accuracy problems and further improvement is necessary.

Josephson junctions with Josephson effect have shown ultimate performances in applications to high-frequency devices, because of the strong nonlinearity resulting from the macroscopic quantum phenomena in the superconductors. In this paper, we review the Josephson effect and Josephson junctions, and introduce high-frequency response properties and applications.