RIKEN-Fujitsu 64-Qubit Superconducting Quantum Computer

Overview

The 64-qubit superconducting quantum computer from RIKEN and Fujitsu is Japan's flagship domestically built machine of its generation. It was installed at the RIKEN RQC-Fujitsu Collaboration Center in Wako, Saitama, in October 2023 with support from Japan's Ministry of Education, Culture, Sports, Science and Technology, and it became the base for a hybrid quantum-classical platform that the partners offer to companies and research institutions.

The machine matters less for its raw specifications than for the pathway it started. Fujitsu and RIKEN have since built a 256-qubit system, announced in April 2025, and they are working toward a 1,000-qubit machine in 2026 and, in Fujitsu's longer-term plan, a system with more than 10,000 qubits by fiscal 2030.

History and background

RIKEN, Japan's largest comprehensive research institution, built a smaller domestic prototype in March 2023. Fujitsu, which has long experience in supercomputing and electronics, joined RIKEN in a collaboration center to develop a larger system. The 64-qubit computer went into operation in October 2023 and was described as Japan's second domestically built quantum computer.

In April 2025 the partners announced the 256-qubit successor at the same site, built with new high-density implementation techniques, and said it would be offered globally from the first quarter of fiscal 2025. A 256-qubit system was also delivered to Japan's National Institute of Advanced Industrial Science and Technology (AIST) in March 2025. In August 2025 Fujitsu began development of a machine with more than 10,000 qubits for fiscal 2030, and RIKEN's collaboration center has been extended through March 2029.

How it works

The machine uses superconducting transmon qubits, circuits cooled to a few hundredths of a degree above absolute zero in a dilution refrigerator. Microwave pulses carried by coaxial lines control each qubit and read out its state. Qubits are organized in unit cells, small repeated blocks that can be tiled to make larger chips.

The key engineering challenge is density. Packing four times as many qubits into the same refrigerator, as Fujitsu did from 64 to 256, requires careful thermal design so that wiring and electronics do not overheat the coldest stage. The partners report a three-dimensional mounting layout in which qubit chips and the wiring layers are stacked, a method that other superconducting groups also use.

The 64-qubit machine is offered as part of a hybrid platform, meaning that users can combine quantum runs with classical simulation. Fujitsu also supplies one of the world's largest quantum simulators, with 40 qubits, which allows developers to test algorithms before using hardware. This is how most users will interact with the system: through software layers that hide much of the hardware detail.

Connectivity

Unit cells of qubits connected in a two-dimensional pattern; the 256-qubit system reuses the same unit-cell design in four-unit cells

Specifications in detail

Key features

• 64 superconducting qubits, deployed in October 2023 with Japanese government support
• A scalable unit-cell design reused in the 256-qubit successor
• Integrated into a hybrid quantum-classical computing platform
• Delivered with Fujitsu's full-stack software, including a 40-qubit simulator
• Roadmaps to 1,000 qubits (2026) and more than 10,000 qubits (fiscal 2030)

Limitations

• Detailed fidelity and coherence benchmarks are less widely published than those from IBM or Google
• Access is oriented toward Japanese and partner institutions and companies
• Scaling past 1,000 qubits requires multi-chip modules or larger refrigerators
• The 1,000-qubit target for 2026 is a plan, not a delivered result

Timeline

What it is used for

• Hybrid quantum-classical algorithms developed with Fujitsu's simulator and cloud tools
• Research on quantum chemistry and larger molecules
• Error-correction experiments planned for the 256-qubit and larger systems
• A national testbed for Japanese industry and academia

How it compares

• Compared with IBM Heron (156 qubits), the 64-qubit system is smaller, though the 256-qubit successor has more qubits.
• Compared with Origin Wukong (72 qubits), it is a similar-scale domestic national platform in a different country.
• Compared with IQM Garnet (20 qubits), it has more qubits and a similar superconducting approach.

Technical notes

Fujitsu and RIKEN emphasize that their qubits are arranged in repeating unit cells, and that the 256-qubit machine uses the same unit cell as the 64-qubit one, with a high-density three-dimensional mounting layout that quadruples the number of qubits. The partners say the denser design still fits within the same dilution refrigerator, which avoids buying a larger cooling system for each generation.

Why it matters

The machine gives Japan a domestic route to superconducting quantum computing, which matters for national technology policy as well as for science. It also shows how a country can combine government support, a national research institute, and a major electronics company.

The plan to scale from 64 to 256 to 1,000 qubits is also a useful test of the unit-cell approach. If the same cell can be tiled while keeping fidelity high, the design will be a credible alternative to those of the larger US companies.

Frequently asked questions

Keep exploring

• Related processor: IBM Heron (r1, r2, and r3)
• Related processor: Origin Wukong
• Related processor: IQM Garnet

This profile is written for educational purposes and summarizes company announcements, published papers, and vendor specification sheets. Last reviewed: September 30, 2026. Figures marked as company-reported have not all been independently verified, and benchmarks differ between vendors, so compare them with care.

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