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Japan has powered up Shunkai, a new full-stack quantum computer that uses neutral atoms held by lasers rather than superconducting circuits. The system’s designers say it will be opened to outside researchers to test and refine quantum error correction and could ultimately scale to 10,000 qubits by March 2031.
What Shunkai is and how it differs
Shunkai is described by its developers as Japan’s first complete neutral-atom quantum computing stack, including control software, hardware, and user interfaces. That combination is intended to make the machine more accessible to researchers than prototype rigs that require specialist expertise to operate.
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Instead of the ultra-cold circuits used by many quantum systems, Shunkai builds its qubits from individual neutral atoms. Those atoms are captured and positioned inside a vacuum using tightly focused laser beams — often called optical tweezers — then driven with microwaves or light to perform quantum operations. Outputs are read by detecting each atom’s fluorescence with a camera.
Why neutral atoms matter
Neutral-atom systems have two practical advantages. First, they can operate at or near room temperature, avoiding some of the extreme refrigeration required by superconducting chips. Second, the physical layout of the atoms can be reconfigured during a run, letting researchers change which qubits interact and program entanglement between particular pairs.
Those capabilities could ease two central challenges in quantum computing: increasing the number of qubits in a single machine, and managing the high error rates that currently limit useful calculations.
Scaling plan and researcher access
Project leaders say Shunkai will initially run with roughly 50 qubits. The short-term upgrade target is about 500 qubits, with a far more ambitious roadmap beyond that.
- Initial operation: ~50 qubits
- Near-term expansion: ~500 qubits
- Long-term goal: 10,000 physical qubits with error detection and correction by March 2031
The team plans to integrate Shunkai into an existing shared supercomputing facility, creating a hybrid center that pairs quantum hardware with conventional GPUs. Japan’s National Institutes of Natural Sciences said partial access will be granted to external researchers so they can develop applications and work on improving the machine’s error-correction performance.
The technical hurdle: fragile qubits and error rates
Qubits remain extremely sensitive. Even small environmental disturbances can collapse the fragile quantum states that carry information. The article notes typical quantum error rates are on the order of one in 1,000 operations, compared with error rates in classical computing that can be as low as one in a billion or one in a trillion.
That gap is why much of the field focuses on quantum error correction — techniques that encode information redundantly across several qubits so that local errors do not spoil an entire calculation.
Voices from the project
Kenji Ohmori, a professor of photo-molecular science at the Institute for Molecular Science and the project lead, said researchers’ use of Shunkai would “lead to ripple effects on various fields in industry, academia, and government around the world.”
Ohmori also framed the effort in modality terms: “Neutral atom-based quantum computers have recently been rapidly attracting attention around the world as a new modality that could exceed the limits of the superconducting modality,” he said, adding that developing Japan’s first full-stack system in this approach is “extremely significant.”
Where Shunkai would sit in the field
If the team reaches its long-term target, Shunkai would surpass the scale of a 6,100-qubit neutral-atom array demonstrated by Caltech researchers in October 2025. Achieving reliable, error-corrected operation at that size would represent a major step toward machines that can tackle problems beyond the reach of today’s fastest classical supercomputers.
For now, the immediate impact is on experiment design and error-correction research. Opening the system to outside teams will let engineers and scientists test algorithms, hardware improvements, and error-mitigation techniques on a working neutral-atom platform.
