The development of fault-tolerant quantum computers that can solve diverse, complex, and large-scale problems is highly anticipated. Achieving this requires both high-fidelity and highly-integrated qubits. Research and development is progressing on various physical systems, and semiconductor qubits are one of the leading candidates. This report provides an overview of the fundamental knowledge of semiconductor qubits. Then, it introduces the global research and development trends related to high fidelity, various efforts toward integration, and research and development of peripheral technologies.

Nearly 40 years after the discovery of high-temperature superconductivity (HTS), a promising application has emerged: compact fusion comprising the use of REBa₂Cu₃O_x (REBCO, RE: rare-earth element) HTS wires. The key technology here is a large and high field HTS magnet, with a supply of REBCO wire extending over several hundred million kilometers. This report presents a review of the technical path toward the mass production of REBCO wires, primarily using the ion beam assisted deposition–pulsed laser deposition (IBAD–PLD) method. Furthermore, the challenges of the wire research and development (R&D) and compact-fusion application prospects are briefly outlined. The effort described in the R&D history should serve as a reference for young researchers, engineers, and entrepreneurs to lead the next generation of industries and economies.

Infrared detectors onboard earth observation satellites are required to have excellent performance. JAXA is studying the Type II superlattice infrared detector as a next-generation infrared detector to replace the HgCdTe detector widely used in conventional earth observation satellites. This paper describes the principle and current development status of the Type II superlattice infrared detector in JAXA.

Synchrotron radiation facilities, which are compared to giant microscopes, are used for cutting-edge research in various fields because the characteristics of the emitted X-rays enable observations with extremely-high resolution that cannot be achieved with laboratory-scale analytical equipment. High-precision optical elements are indispensable to obtain this high resolution, and the author’s company is the only one that provides a stable supply of X-ray total-reflection mirrors with surfaces smoothed to a remarkable accuracy of less than 2 nm. This paper describes the existence of a unique nanofabrication technology behind this global niche top business, its successful practical application and commercialization, and introduces an example of an application development of the new technology.

In this article, nonvolatile memory transistors using Hf-based ferroelectric thin films are described. Ferroelectric-gate transistors, metal–oxide–Si field-effect transistors, are explained using ferroelectric HfO₂ and HfN thin films, which can be formed directly on the Si substrate as a gate insulator. Furthermore, FeNOS-type nonvolatile memory transistors that is the metal–oxide–nitride–oxide–Si-type flash memory with ferroelectric HfO₂ thin films, which achieves precise threshold voltage control using polarization and charge trap characteristics, are explained.

Dirac semimetals have a so-called Dirac cone in their three-dimensional bulk electronic structures. They also have a unique bulk–surface coupled electronic state. Consequently, they have attracted growing attention as a material system for next-generation electronics. In this review, we will explain the fundamental features of Cd₃As₂, a typical Dirac semimetal, and introduce various results ranging from the fabrication of high-quality thin films to the determination of a unique quantum Hall state. We will also summarize future prospects for possible applications.

Non-equilibrium plasmas are characterized by high electron temperatures (tens of thousands of degrees) and low gas temperatures (about room temperature), and thereby, are termed as low-temperature plasmas. High-energy electrons collide with gas atoms and molecules to produce ions, excited species, and reactive species to accelerate chemical reactions, which are used in a wide range of environmental, medical, and agricultural applications, such as sterilization, cancer treatment, and plant disease control. Furthermore, they are used in the applications for materials science involving thin film growth and nanomaterial synthesis. Additionally, high reactivity and controllability can be realized by physically controlling the behavior of electrons and ions by means of electric and magnetic fields. In this review, the methods for physically and chemically controlling plasmas are described, and applied research, utilizing controlled non-equilibrium plasmas, is introduced.

The superconducting diode effect (SDE) is a phenomenon that results in a superconducting state with zero electrical resistance in the forward direction, but a normal conducting state with finite resistance in the reverse direction. The similarity of this effect to the operation of a semiconductor diode, which is one of the building blocks of modern electronic devices. Exploiting the SDE is promising for the development of diodes and rectifiers with ultra-low power consumption. Recently, a method for controlling the zero-field SDE using magnetization has been demonstrated. This opens up new possibilities for using magnetization to control superconductivity. Here, we provide an overview of the SDE and discuss its future prospects.

Defect-structure-type proton conductors are ceramics in which hydrogen ions (protons) dissolve in oxides and diffuse in the crystal. The material has attracted considerable attention as an electrolyte for hydrogen sensors and fuel cells. In this review, the material properties and polarization characteristics of defect-structure-type proton conductors will be described, and the application to hydrogen sensors and fuel cells will be introduced.

NanoTerasu is expected to start operation in April 2024. It is a next-generation synchrotron radiation facility constructed at Tohoku University Aobayama New Campus (Sendai City). Regarding synchrotron radiation facilities, SPring-8 in Hyogo Prefecture, which began operation in 1997, is well known to the general public. After approximately a quarter of a century, the new facility of NanoTerasu was established and will be operated by the government. The accelerator technology that produces light is based on the unique technology of synchrotron radiation science in Japan, which has been refined at SPring-8. However, SPring-8 and NanoTerasu have different uses; SPring-8 has capability in using hard X-rays, whereas the strength of NanoTerasu lies in using soft X-rays. Leveraging this strength, we are aiming to contribute to solving social issues such as the creation of a carbon-neutral society. In this article, our challenges with NanoTerasu are described in detail.

Graphene is a carbon-based, atomically thin, two-dimensional material that exhibits remarkable optical and electronic properties that have not been demonstrated by conventional bulk materials. In particular, its broadband photodetection capability, high carrier mobility, and low environmental impact are advantageous for infrared (IR) sensor applications. This paper discusses the prospects and challenges of graphene-based optical sensors. In addition, the photodetection mechanism of graphene-based optical sensors is explained. Subsequently, a promising optical-sensor performance-enhancing method of photogating is discussed. Finally, graphene-photogated diodes (GPDs), which exhibit high responsivity and low dark current, and graphene-based IR image sensors using an array format of such GPDs are reviewed.

Thermal energy is generated by all activities that consume energy and dissipate into the environment. However, for the proper function and performance of logic semiconductors, power semiconductors, optical devices, and living organisms, it is important to manage heat appropriately. Accurate understanding of thermal transport requires a deep understanding of the behavior of phonons, which are heat carriers. Phonons are more difficult to track and control than photons or electrons, but the exploration of their unique physics and development of control technologies are progressing steadily. Various applications have been introduced, owing to the understanding and control of thermal phonons, based on the fundamentals of thermal phonon transport at the nanoscale.

In recent years, the rapid advancements in machine learning have significantly influenced its broader application within society. Concurrently, the prospects of utilizing the computational strengths of quantum computers for machine learning have been a focal point since the 2010s. As quantum hardware continues to evolve, a notable shift is occurring toward developing algorithms specifically for current and near-future quantum systems. This article presents a concise overview of machine learning assisted by quantum computing.

The radio radiation protection guidelines and evaluation methods for the human safety assessment of wireless power transmission using microwaves are described. Microwave power transmission has been institutionalized among wireless power transmissions, and human safety evaluation is required for its operation. This paper introduces radio radiation protection guidelines, their evaluation procedures, and trends in their international standardization.

Owing to its high carrier mobility and weak interaction with phonons, graphene demonstrates remarkable carrier dynamics in the terahertz (THz) range. Our recent experimental results for the active spatial control of graphene plasmons and ultrafast optical-to-electrical conversion processes in graphene photodetectors are presented herein, in addition to an explanation of the on-chip THz spectroscopy method developed for the time-domain measurement of ultrafast electrical currents excited at the photodetector.

Inorganic nanoparticles made of inorganic materials are difficult to arrange in an ordered manner and form higher-order structures by themselves. However, surface modification with DNA, which has selective binding properties, as a guiding molecule can control the interaction and binding between nanoparticles to assemble them into desired crystal structures. In this report, the author presents recent work on determining the structural conditions for DNA-functionalized nanoparticle superlattices that can maintain crystalline symmetry not only in the hydrated state but also after drying by precisely characterizing crystallinity using small-angle X-ray scattering.

This paper reviews our recent research about the formation and optical characteristics of GaN:Eu/GaN nanowires (NWs) by organometallic vapor phase epitaxy for application in GaN-based red LEDs. Two types of GaN:Eu/GaN NWs with different configurations are introduced, core–shell and axial geometries. The configuration of GaN:Eu layers on GaN core NWs can be controlled by changing the growth conditions, and affects the properties of Eu luminescence in the GaN NWs. Next, the fabrication process of the NW LEDs towards future possible realization of flexible devices is established, including an etch-back process of the PDMS membranes to expose the top p-GaN contact layers. Finally, a prototype of p-GaN/GaN:Eu/n-GaN NW LEDs on sapphire substrates is fabricated to determine the device characteristics. Sharp red luminescence at room temperature from Eu³⁺ ions is observed under current injection.

Using molecular beam epitaxial crystal growth, we synthesized large-capacity, high-quality compound semiconductor GaAs-based nanowires on a 2-inch silicon substrate. In addition, we explored novel nanowire materials through the growth of GaInNAsBi compounds, crystal polymorphism including stable zincblende and metastable hexagonal structures, and material conversion by oxidation. These materials show various potential applications as a light source in the near-infrared band or white light, and exhibit nonlinear optical effects.

We present the size effects on the electrical and optical properties of high Hall mobility transparent conductive oxide (TCO) films, where the size effects were characterized by the disorder parameter. First, we deposited amorphous W-doped In₂O₃ (IWO) films with thicknesses ranging from 5 to 10 nm on glass substrates using reactive plasma deposition with dc-arc discharge. Then, we obtained polycrystalline IWO films by solid-phase crystallization, and elucidated the dominant factors determining the states of the carrier electrons and their carrier transport of the films. Decreasing the thickness from 10 to 5 nm, while retaining the carrier concentration, leading to a 2D-like films with induced a lattice disorder, resulting in reduced Hall mobility. A theoretically obtained electron–phonon coupling factor, which is found to be governed by the Debye temperature, carrier concentration, and disorder parameter, provided the cause of the above carrier transport behavior. In addition, based on the above electron–phonon coupling factor, we propose theoretical predictions of materials design to achieve high carrier transport ultra-thin TCO films.

Most electrolytes increase the surface tension of water. According to thermodynamics, this leads to a repulsive force between the gas–liquid interface and the ions. The thermodynamic properties and the computational theory of surface tension are first introduced. Subsequently, a quantitative comparison of ion adsorption for individual ion species is presented based on a theoretical analysis of experimental data. The analysis of experimental data on surface tension and contact angle at the oil–water interface and hydrophobic solid–liquid interface also reveals the universal nature of the interaction between ions and hydrophobic interfaces.

Optical observation of ultrathin crystals on substrates is important in research on layered materials. Ultrathin crystals are conventionally visualized using the optical interference effect in thermally-grown silicon substrates. Herein, a visualization technique that focuses on the optical properties of the substrate was developed. This method allows recognition of a monolayer and reliable identification of the number of layers in hexagonal boron nitride crystals. Furthermore, the difference in the thickness of the monolayer in a thick crystal was visualized, enabling the selection of mechanically exfoliated crystals.