(From left) Yuetsu Komada, Mitsuhisa Sato and Tamiya Onodera. © 2026 RIKEN
A pioneering project led by RIKEN is underway to develop software to integrate quantum computers with supercomputers efficiently. Leading the project are three figures from the Quantum High-Performance Computing Collaboration Platform Division at the RIKEN Center for Computational Science, in Kobe, Japan.
These lead researchers include Division Director Mikihisa Sato and Deputy Director Yusuke Kodama, both of whom contributed to the development of one of the world's fastest supercomputers, supercomputer Fugaku, and Deputy Director Tamiya Onodera, who joined the division in April 2025 after working at a quantum research lab in Tokyo for global tech giant IBM.
We spoke with all three researchers about their project's goals and key aspects of their research and development:
Parallel growth
By leveraging quantum superposition-which allow quantum computers to process multiple possibilities simultaneously-a new range of quantum computers can process vastly more information than conventional computers, which only handle one data state at a time. This means that quantum computers have the potential to solve problems that are extremely challenging for conventional computers at high speed.
Current quantum computers use a range of strategies and technologies to achieve this feat, including ion traps, superconducting circuits, optics, and silicon-based approaches.
Given their increasingly impressive performance today, some may wonder why quantum computer integration with supercomputers is necessary at all. However, quantum and conventional computers-including supercomputers-excel in fundamentally different areas, so each has unique strengths and weaknesses.
Supercomputers excel at general-purpose tasks, large-scale simulations, and processing massive datasets reliably. Quantum computers, while powerful at solving specific problems, are still experimental and not suited for broad, data-heavy or routine computing tasks.
Mikihisa Sato, division director of the Quantum High-Performance Computing Collaboration Platform Division, adds that while quantum computers can solve problems that supercomputers struggle with, they currently only function usefully when controlled by conventional computers.
"In the future, as quantum computers improve ten-fold or even a hundred-fold, control and communication will require much more help from supercomputer-level computing," he says.
An example of a quantum computer program. The horizontal lines represent each qubit (the figure shows 5 qubits), and the operations indicated by symbols such as H and S are applied sequentially from left to right. The meter symbol at the right end indicates that the qubits are measured and read out as either 0 or 1. © 2026 RIKEN
Options explosion
Supercomputers on the other hand currently struggle in fields where a 'computational explosion' is occurring, explains Sato. For example, choosing 10 binary options yields 210 or 1,024 combinations-which is manageable for conventional computers. But with 20 binary options, the combinations jump to 220 or 1,000,000, and the number of combinations grows exponentially, requiring enormous computation time.
Quantum computers excel in these scenarios. Thus, they are particularly valuable when processing problems with many potential combined options as solutions. This ability is particularly useful to materials development, drug discovery, artificial intelligence, and optimization processes that involve many combinations.
By delegating the most challenging calculations to quantum computers, overall processing efficiency is improved, says Sato.
Currently, leading quantum computers, such as those produced by American technology company IBM, are modest in size. They have just surpassed 100 qubits-with qubits being in some ways analogous to the bits used in conventional computers to store information and perform calculations.
However, unlike bits, which are either 0 or 1, qubits can exist in multiple states at once. This allows quantum computers to process complex problems faster than classical computers in specific scenarios.
However, Sato notes that quantum computers require the input of conventional computers to understand and execute commands. To use an analogy: if a quantum computer is like a piano and its program is the sheet music, the conventional computer is the pianist who plays the keys, he explains.
Thus, as the number of qubits in quantum computers increase to 1,000 or even 10,000, the inclusion of supercomputer-level performance computers will be essential to their effective operation.
Developing software
The RIKEN-led JHPC-quantum (Research and Development of quantum-supercomputers hybrid platform for exploration of uncharted computable capabilities) project aims to develop the fundamental system software needed to link quantum computers and supercomputers.
System software manages basic computer operations and enables other software to function.
A five-year project that launched in November 2023, the project is a collaboration between RIKEN, the University of Tokyo, Osaka University, and SoftBank Corporation, a Japanese tech company focused on telecommunications that is headquartered in Tokyo. SoftBank are responsible for finding ways to apply the project's results to industry.
So far, two types of quantum computers have been deployed. The Reimei, which is an ion trap type of quantum computer, was developed by Quantinuum-a global quantum computing company formed through the merger of Honeywell's quantum division, known for its advanced hardware, and Cambridge Quantum, a UK-based company specializing in quantum software and algorithms. Reimei was introduced in February 2025 at RIKEN's Wako campus, and it uses tiny, charged atoms (called ions) held in place by electric fields and controlled with lasers to perform calculations.
The second is IBM's superconducting-type IBM Quantum System Two, known as ibm_kobe, introduced in June at RIKEN's Kobe campus. This system uses ultra-cold electrical circuits that allow electricity to flow without resistance, enabling quantum operations.
The project is looking at both types of quantum computers because it is still unclear which technology will become mainstream, explains division deputy director Tamiya Onodera. Focusing both ensures software compatibility regardless of future developments. "Superconducting quantum computer types will likely achieve more than 10,000 qubits, but no one really knows which technology will reach one million qubits," he says.
The two systems are currently being tested by 12 user groups, including researchers and institutions, to explore how they can be used in fields like science, medicine, and technology. "From now on, actual evaluations will be conducted using the programming environment on the system software we have developed," says Kodama.
IBM Quantum System Two (pictured), installed at RIKEN's Kobe campus, uses superconducting qubits cooled to near absolute zero to perform quantum operations. © 2026 RIKEN
A pioneering effort
Globally, there is a growing movement to introduce quantum computers to computer centers traditionally focused on supercomputers, where they are often assigned specific calculations. This project, however, enables direct contact between the quantum computer and supercomputer via a program, allowing only key parts to be computed quantum mechanically.
"Our project is the only one globally attempting large-scale, tightly integrated collaboration between quantum computers and supercomputers," says Sato. "In that respect, we are ahead of other efforts around the world."
The goal is to demonstrate that collaborating quantum computers with supercomputers is more effective than using supercomputers alone.
"There are many discussions about what quantum computers will be able to do in 10 years. But there are very few answers to 'What can they do now?' Through this project, we want to clearly show how useful today's quantum computers are," says Sato.
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About the authors
Mitsuhisa Sato, Division Director
Mitsuhisa Sato has been the division director of the Quantum-HPC Hybrid Computing Platform Division in RIKEN Center for Computational Science (R-CCS) in Kobe since 2023. He received his PhD in information science from the University of Tokyo in 1990. From 2014 to 2020, he worked as the team leader of the architecture development team on the FLAGSHIP 2020 project to develop the Japanese supercomputer, Fugaku. He was appointed deputy director of R-CCS, a position he held from 2018 to 2022. Since 2023, he has been a professor at Juntendo University in Tokyo and a professor emeritus of the University of Tsukuba in Tsukuba.
Tamiya Onodera, Deputy Division Director
Tamiya Onodera has been a deputy division director of Quantum-HPC Hybrid Platform Division at the RIKEN Center for Computational Science (R-CCS) since April, 2025. Prior to RIKEN, he managed the Quantum Computing group at IBM Research - Tokyo. With more than 35 years of experience in the IT industry, his research interests include programming languages, middleware and software stacks for quantum computers. He currently serves as secretary of the Special Interest Group on Quantum Software of Information Processing Society of Japan (IPSJ). Tamiya is a distinguished scientist of the Association for Computing Machinery (ACM), and a fellow of the Japan Society for Software Science and Technology (JSSST).
Yuetsu Kodama, Deputy Division Director
Yuetsu Kodama has been a deputy division director at the RIKEN Center for Computational Science (R-CCS) in Kobe since 2024, leading the Quantum-HPC Hybrid Platform Division. He has been a senior scientist at RIKEN R-CCS since 2015. He received a PhD in engineering from the University of Tokyo in 2003. He was a professor at the University of Tsukuba between 2011 and 2015, a senior researcher at AIST (National Institute of Advanced Industrial Science and Technology) between 2000 and 2011 and a senior researcher at a former electrotechnical research body, ETL (Electrotechnical Laboratory) between 1988 and 1999. He has been engaged in the research on parallel computer architecture. He is a member of IEEE Computer Society, Institute of Electronics, Information and Communication Engineers and Information Processing Society of Japan.
