One hundred years after the birth of quantum mechanics, quantum computers, which harness the mysterious properties of quantum mechanics for information processing, are becoming a reality. Although many challenges remain, quantum computers are steadily evolving, and it is expected that in the near future, they will solve problems beyond the reach of conventional (classica) computers. In this comprehensive report, we present the trajectory from the birth of quantum mechanics to the rise of quantum information science, the development of quantum computers, and the outlook for the future, including both domestic and international trends.

Superconducting qubits are one of the promising hardware candidates for quantum computing, and the operation of quantum processors equipped with more than 1000 qubits have been reported. However, to achieve a meaningful quantum computation that has an advantage over classical computation, further improvement in gate fidelity and more precise control of circuit parameters are required, and many challenges remain in realizing such hardware. In this article, we summarize the current status and challenges of superconducting qubits with a focus on the circuit fabrication process and present our research and development of superconducting qubits using nitride superconductors.

We report on an ion-shuttling experiment which is one of the core technologies in large scale ion-trap quantum computers. By controlling voltages applied to five pairs of electrodes in an on-chip ion trap, we have demonstrated shuttling of a single calcium ion. Besides the experimental result, we introduce discussion of the relation between ion motion and the condition of surface of trap electrodes and discuss the vacuum techniques which are required for scaling up of ion-trap quantum computers.

Silicon quantum computers are still in the early stages of development. It is expected that mature semiconductor technology will be applied in the future, and large-scale integration will progress. In this paper, after explaining the operating principles of silicon qubit devices, the current status of research and development on increasing the fidelity and integration of qubits is introduced. Future challenges and prospects are also discussed.

Majorana particles (or Majorana Zero Modes (MZMs) in solid state materials) emerge in topological superconductors and are attractive for topological quantum computing as well as for fundamental solid state physics study. The topological superconducting states can be designed by inducing superconductivity in topological insulators or semiconductor nanowires. We show a basic idea of topological quantum computing with the MZM, show how it can emerge in the materials, and show our current effort to detect it with the Josephson junction devices.

Cryogenic-CMOS (Cryo-CMOS) technology has attracted a lot of attention for large-scale integrated quantum computers. For an accurate design of cryo-CMOS circuits operating at 4 K, understanding the device performance at cryogenic temperatures is required. However, the performance of cryo-CMOS devices is significantly different from that of CMOS devices operating at room temperature, and it is difficult to reproduce the cryogenic current-voltage characteristics using existing models as is. In recent years, great efforts have been made to obtain a physical understanding of cryo-specific performance. This paper provides an overview of the operation of cryo-CMOS devices and presents recent progress on its physical understanding with a particular focus on the influence of the oxide/Si interface.

In recent years, optical tweezer arrays of neutral atoms have attracted much attention as a platform for implementing quantum computers. The neutral atom quantum computers are a promising candidate for fault-tolerant quantum computation due to their high controllability and scalability based on the technique of reconfigurable optical tweezers array and the use of Rydberg states to realize a two-qubit gate between two distant atoms in the optical tweezers. In this paper, we will give an overview of the neutral atom quantum computer and its technical issues and introduce our research using atoms in an optical tweezer array.

In order to secure the sample to the sample holder and create a structure that serves as a partition between the gas introduction system on the back of the sample and the ultra-high vacuum measurement chamber, a vacuum seal must be completed at the same time as the sample is fixed. We searched and tried sealing methods to perform permeation measurements on samples with several mm size, since standardized products such as international ConFlat flanges cannot be used for the vacuum seals in these size.