RIKEN runs five silicon spin qubits on one microwave line at fault-tolerant fidelity

Researchers at RIKEN operated five silicon spin qubits in parallel on a single microwave line while holding fault-tolerant fidelity. Three-qubit operation exceeded 99.99% single-qubit gate fidelity, and four of five qubits topped 99.9% in full parallel operation. The study was published in Nature Physics on October 15, 2026.

• Three-qubit operation exceeded 99.99% single-qubit gate fidelity
• Four of five qubits topped 99.9% in parallel operation
• Pairwise calibration needs 20 measurements, not 32 combinations
• Best qubit Q3 reached 99.9987% fidelity