INTERVIEW | The Next Step for Japan's Quantum Computers with Yasunobu Nakamura

The quantum computer is a next-generation computational structure that is expected to solve societal problems. It uses the unexpected properties and principles of quantum mechanics to perform calculations that are impossible even for today's supercomputers.

Amid intensifying global competition to develop this technology, RIKEN, which is leading Japan's research efforts into quantum computing, put three domestically-produced machines into operation in 2023. What will be their next move in 2024? The Sankei Shimbun and JAPAN Forward asked Dr Yasunobu Nakamura, Director of the RIKEN Center for Quantum Computing.

A Step in the History of Quantum Computers

In March 2023, the RIKEN Center for Quantum Computing publicly released a cloud-based quantum computer. Developed in collaboration with Fujitsu and other companies, it was the first domestically-produced quantum computer. In October, the second unit, which was based on the first, went into operation. While the first machine was primarily for universities and research institutes, the second was aimed at companies that are developing applications for quantum computing.

Companies such as Fujifilm and Tokyo Electron are participating in the joint research project. Their applications include materials development, financial engineering, and data science.

Furthermore, in December, a research team from Osaka University, RIKEN, and others installed and began operation of a third machine at Osaka University.

All three units are based on the superconducting method that Dr Yasunobu Nakamura has been researching for many years. Also, service is being expanded for using the computer through the cloud. Furthermore, this can be extended beyond the laboratory to include industry, laying a foundation to accelerate research and development using the computer while also exploring societal implementations. This initiative, whereby a country maintains a flagship machine and releases it via the cloud to the public, is nearly unprecedented.

A Domestically-Produced Quantum Computer

Dr Nakamura commented on the attention the operation of the domestically-produced machine has attracted. He said, "I am happy that it is drawing attention, but this is just one step in the history of quantum computers. We have been working on improving performance since we began. However, we are considering how to further scale up during 2024. The more important point is to improve the quality."

Boosting the quality means reducing computational errors. Qubits, the basic elements of a quantum computer, are vulnerable to noise and prone to errors in the calculation process. Suppressing errors to derive the correct answer is one of the most important development issues for quantum computers.

Although several months have passed since it was released to the public, users have not expanded beyond those working on research collaborations. Dr Nakamura said, "We are gradually increasing the number of people using the cloud. But we must further improve usability. It will take a little more time to extend the usage (beyond current collaborators)," he said.

*Caption: Nakamura, director of the RIKEN Center for Quantum Computing and professor at the University of Tokyo. December 2023. (© Sankei by Maki Matsuda)*

Examining the Fundamental Physics

In the aim for societal implementation, there is a push to link conventional computers including supercomputers (known as classical computers) with quantum computers. In this regard, Dr Nakamura emphasizes, "Having our own quantum computer is a great advantage."

There are a growing number of commercial quantum computer options in the world. However, they tend to be black boxes, making it difficult to intervene in their inner workings. A machine that is developed and operated in-house can be controlled at the physical level. It can also be better connected to classical computers.

When asked about his goals, Dr Nakamura said, "My short-term goal is to make quantum computers even better. Then, we want to connect this to new discoveries in physics."

The idea for the quantum computer was born from a physical theory. If the level of engineering can be raised to realize these theories, new physics ideas may emerge. "This is how science has progressed," says Dr Nakamura.

Quantum computers are generating enthusiasm due to their significant impact on social and economic activities. Dr Nakamura has the outlook of a physicist working to get to the essence of the science, while also keeping his place in this active field.

(Read the report in Japanese.)

Author: Maki Matsuda