RIKEN-Fujitsu 256-qubit superconducting quantum computer
RIKEN-Fujitsu 256-qubit superconducting quantum computer
Register profile — the machine's variant of its architecture
qubit type: transmon
gate mechanism: coupler type not published
connectivity: scalable 3-D connection structure tiling unit cells
control: Keysight control electronics (secondary); perpendicular wiring; implementation density quadrupled inside the same dilution refrigerator
control placement: room-temp
readout: dispersive
gate evidence: no published figure
flags: cryogenic details missing, no published error rates
Technologies by layer — the machine's cell per layer
| 1 Qubit carrier | |
| 2 Encoding | Bare physical qubit (no encoding) · primary ◌ 🔎 Bare two-level subspace — Computational subspace of an anharmonic oscillator; leakage to |2⟩ is the price. |
| 3 Gate mechanism | — undisclosed — exists, nothing published ▨ 🔎 gate mechanism and coupler type not published; no fidelities published |
| 4 Connectivity / transport | Static nearest-neighbour lattice · primary ▥ §Scalable 3D connection structure (4-qubit unit cells arranged in a 3D configuration) ✅ 4-qubit unit cells tiled in a scalable 3-D connection structure; 4× qubits with no redesign of qubit or unit cell |
| 5 Control | Vertical (out-of-plane) signal delivery — VIO, coaxmon, 3D wiring · primary ▥ §High-density implementation (quadrupled density in the same dilution refrigerator; thermal design) ✅ perpendicular wiring with high-density packaging; implementation density quadrupled inside the same dilution refrigerator Room-temperature electronics + per-qubit coax/flex · alternate ▨ 🔎 room-temperature control; Keysight control electronics (secondary) |
| 6 Readout | |
| 7 Code | — none — nothing in this layer ▨ 🔎 no QEC code run (NISQ); QEC stated intent only, no result as of Sep 2026 |
| 8 Decoder | |
| 9 Interconnect | |
| 10 Manufacturing |
evidence: ✅ 2 / 12
Pictures
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