Japan Launches Shunkai Neutral-Atom Quantum Computer

Japan’s Institute for Molecular Science (IMS) has announced the operation of Shunkai, the country’s first full-stack neutral-atom quantum computer. Developed by a team under Professor Kenji Ohmori, the machine initially features approximately 50 qubits and integrates control hardware and software. Hitachi contributed to the software stack, while Infleqtion provided the processor. Future plans, including an expansion to 500 qubits and a 10,000-qubit fault-tolerant target, are part of the Moonshot program timeline, not yet demonstrated capabilities.

Operational particulars

According to the August 24 press release, Shunkai utilizes neutral atoms held in optical tweezers as qubits, controlled by microwaves and laser light, with readout achieved by imaging fluorescence from individual atoms. The current system employs about 50 qubits. IMS labels it “full-stack” because it translates user inputs through various layers into signals executable by the processor, then returns the output.

The announcement didn’t include performance data such as gate fidelity, coherence time, or benchmark figures, nor is there an accompanying paper. Therefore, the “operational” claim signifies that the machine is running and producing output, but doesn’t provide details on its computational efficiency or how it compares to other neutral-atom systems. A 50-qubit count is modest for this modality, as groups like QuEra have already operated neutral-atom arrays with hundreds of qubits.

This project falls under the Cabinet Office and JST Moonshot R&D Program, Goal 6, which aims to develop a fault-tolerant universal quantum computer. IMS also mentioned a planned collaboration with Yaqumo Inc., a company founded by Ohmori, where he serves as an executive advisor. This founder’s stake in a named partner is explicitly stated in the release.

Roadmap versus reality

IMS intends for Shunkai to scale to approximately 500 qubits, then to 10,000 physical qubits with error detection and correction by March 2031. These are targets for the second phase of the Ohmori project, which began in April 2026. Error correction for this system is described as a feature that external users will help develop and demonstrate, indicating it is not currently implemented.

Ohmori commented on this milestone in the release:

“I think it is extremely significant that now we have developed Japan’s first full-stack quantum computer in this cutting-edge modality and started its operation.”

This statement comes from an involved party in the program. The concrete news is the operational 50-qubit machine, which will be partially accessible to external users. The remaining aspects constitute a five-year plan without published data to assess its progress.