Most quantum computers sit inside dilution refrigerators near absolute zero (~15 millikelvin, roughly 200 times colder than outer space), because heat is noise and noise destroys fragile quantum states. Japan's newly commissioned machine, Shunkai, runs in a room-temperature laboratory — because what traps its atoms is not metal, but light.
Why quantum computers are usually so cold
Mainstream superconducting machines (IBM, Google) need massive, kilowatt-consuming cryostats, making scaling an engineering nightmare. The neutral-atom approach avoids refrigeration entirely: atoms are suspended in vacuum and held by laser "optical tweezers," so ambient temperature does not directly disturb them.
How neutral atoms become qubits
1. Highly focused lasers form optical tweezers that individually trap single atoms in vacuum. 2. Atoms are levitated and arranged into arrays; each atom is one qubit. 3. Microwave or laser pulses drive quantum gates. 4. Cameras read out fluorescence from each atom to extract results.
Native advantages of the neutral-atom route:
- Room-temperature operation, no cryostat
- Moving atoms enables entanglement between any two qubits
- Qubit positions can be rearranged flexibly per algorithm
- Easy scaling — add more optical tweezers
- Long qubit coherence lifetimes
- Software stack: Hitachi
- Quantum processing unit (QPU) hardware: Infleqtion (US neutral-atom leader)
- Academic lead: Kenji Ohmori's team at the Institute for Molecular Science (IMS), under Japan's Moonshot R&D Program Goal 6 (fault-tolerant universal quantum computing)
- Initial: ~50 physical qubits
- Near-term expansion: ~500 qubits
- By March 2031: 10,000 physical qubits with quantum error detection and correction
- Different route: neutral atoms (room temperature, optical tweezers) — not superconducting or trapped-ion
- Different country: Japan's first full-stack machine, a Moonshot Goal 6 national project
- Different architecture: transnational full-stack combining Hitachi software with Infleqtion hardware
- Different signal: "10,000 qubits + fault tolerance by 2031" written into an official roadmap
What "full-stack" means
Shunkai is not just hardware; it integrates the entire chain from user input to computed output:
This "academia-led + Japanese software + US hardware" combination reflects Japan's quantum strategy: assemble the world's strongest modules into its own full-stack machine. The name Shunkai honors Edo-period astronomer Harumi Shibukawa, creator of Japan's first indigenous calendar.
Roadmap: from 50 to 10,000
Useful quantum computing requires logical qubits — many error-prone physical qubits encoded into one reliable one. The 2031 fault-tolerance milestone places Shunkai on the same timeline race as IBM and Google.
Open access and industrialization
Shunkai is not a showpiece. IMS states the system will be partially opened to external researchers for:
1. Application development — running real algorithms 2. Quantum error-correction demonstrations and improvements on real hardware
Ohmori's team has also incubated Yaqumo Inc. (Ohmori as founder and executive advisor) to push the machine toward real-world deployment.
How it differs from other recent quantum news
Quick glossary
> Optical tweezers: tightly focused laser light forming a potential well that levitates and moves tiny particles (atoms, cells); recognized by the 2018 Nobel Prize in Physics. > > Physical vs logical qubits: physical qubits are real, error-prone hardware units; logical qubits are redundantly encoded "reliable qubits" — the currency of useful computation. > > Quantum error correction (QEC): redundant encoding plus periodic error detection to push error rates below threshold, making long algorithms feasible.
References
1. Institute for Molecular Science (IMS) / NINS press release on the commissioning of Shunkai, Japan's first full-stack neutral-atom quantum computer. 2. Ohmori K. team, Moonshot R&D Program Goal 6: large-scale, high-coherence fault-tolerant quantum computers (dynamic atom arrays). 3. Infleqtion announcements on the Japan quantum Moonshot collaboration (neutral-atom QPU stack). 4. Hitachi, Ltd. announcements on the Shunkai software stack. 5. Background: 2026 industry overview of neutral-atom quantum computing (QuEra / Pasqal / Atom Computing / Infleqtion route comparison).