Shunkai: Japan's Full-Stack Neutral-Atom Quantum Computer Runs at Room Temperature

Forum topic · QianXun · 2026-08-24

Summary

Japan has begun operating Shunkai, a full-stack neutral-atom quantum computer that, unlike superconducting machines from IBM or Google, runs at room temperature without a dilution refrigerator. Neutral-atom systems trap individual atoms in vacuum using focused laser optical tweezers, where each suspended atom serves as a qubit, quantum gates are driven by microwave or laser pulses, and results are read out via fluorescence imaging. The project is led by Kenji Ohmori's team at the Institute for Molecular Science (IMS) under Japan's Moonshot R&D Program Goal 6, with Hitachi providing the software stack and US-based Infleqtion supplying the quantum processing unit hardware. Shunkai launches with roughly 50 physical qubits, plans to scale to about 500, and targets 10,000 physical qubits with quantum error detection and correction by March 2031. IMS says the system will be partially opened to external researchers for application development and error-correction work, while spinoff company Yaqumo Inc. drives industrial adoption, positioning Japan alongside IBM, Google, Pasqal, and QuEra in the race toward fault-tolerant quantum computing.

Most quantum computers sit inside dilution refrigerators cooled to roughly 15 millikelvin—about 200 times colder than outer space—because superconducting qubits (the approach used by IBM and Google) are destroyed by thermal noise. Japan's newly operational machine, Shunkai, takes a different route: it is a neutral-atom quantum computer that runs in an ordinary room-temperature lab, because its qubits are held not by metal circuits but by light.

Why neutral atoms don't need a refrigerator

Superconducting qubits are like delicate pendulums in a freezer: any heat scrambles them, requiring kilowatt-scale, human-sized cryostats per machine.
Neutral-atom qubits are like glass beads suspended in vacuum, held by focused laser "optical tweezers." Because they already operate in vacuum and work via light, ambient temperature does not directly disturb them.

How atoms become qubits

1. Highly focused lasers form optical tweezers that individually trap single atoms in vacuum. 2. Atoms are suspended and arranged into arrays—each atom is one qubit. 3. Microwave or laser pulses drive quantum gates. 4. Cameras capture each atom's fluorescence to read out results.

Native advantages of the neutral-atom approach:

Room-temperature operation, no cryogenics
Atoms can be moved to entangle any pair of qubits
Qubit positions can be rearranged per algorithm
Easy scaling (add more tweezers)
Long coherence lifetimes per qubit

What "full-stack" means here

Shunkai integrates the entire chain from user input to computation output:

Software stack: Hitachi
Quantum processing unit (QPU) hardware: Infleqtion (US neutral-atom leader)
Academic lead: Kenji Ohmori's team at IMS, under Japan's Moonshot R&D Program Goal 6 (fault-tolerant universal quantum computing)

This "academia-led + Japanese software + US hardware" assembly reflects Japan's quantum strategy: combine the world's strongest modules rather than build everything in-house.

Roadmap: from 50 to 10,000 qubits

Initial operation: ~50 physical qubits
Near-term expansion: ~500 qubits
By March 2031: 10,000 physical qubits with quantum error detection and correction

Why emphasize *physical* qubits and error correction? Useful computation requires logical qubits—each reliable logical qubit encoded across many error-prone physical qubits. The 2031 fault-tolerance milestone puts Shunkai on the same timeline as IBM and Google.

Open access and industrialization

Shunkai is not just a showcase. IMS states the system will be partially opened to external researchers for:

1. Application development — running real algorithms 2. Quantum error-correction demonstration and refinement on real hardware

Ohmori's team has also incubated Yaqumo Inc. (with Ohmori as founder and executive advisor) to push the machine toward real-world deployment.

How it differs from other recent quantum news

Different modality: neutral atoms (room temperature, optical tweezers), not superconducting circuits or trapped ions
Different country: Japan's first full-stack machine, a national Moonshot Goal 6 project
Different architecture: a cross-border full stack combining Hitachi software and Infleqtion hardware
Different signal: "10,000 qubits + fault tolerance by 2031" written into an official roadmap

Three key terms

> Optical tweezers: highly focused laser light forms an optical potential well that suspends and moves tiny particles such as atoms or cells. A 2018 Nobel Prize in Physics achievement. > > Physical vs. logical qubits: physical qubits are real hardware units that are error-prone; logical qubits are reliable qubits redundantly encoded from many physical ones—the currency of useful computation. > > Quantum error correction (QEC): redundant encoding plus periodic error detection keeps error rates below threshold, making long computations feasible.

References

1. Institute for Molecular Science (IMS), National Institutes of Natural Sciences, press release on the operation of Japan's first full-stack neutral-atom quantum computer "Shunkai." 2. Ohmori K. team, Moonshot R&D Program Goal 6, "Large-scale high-coherence fault-tolerant quantum computers (dynamical atomic arrays)." 3. Infleqtion, participation in Japan's quantum Moonshot (neutral-atom QPU stack). 4. Hitachi, Ltd., announcement of software stack collaboration for Shunkai. 5. Background: neutral-atom quantum computing industry overview (QuEra / Pasqal / Atom Computing / Infleqtion roadmap comparison).