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.

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.

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.

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.