Researchers at RIKEN, Japan’s national research institute, say they have controlled five silicon spin qubits at the same time through a single shared control line while keeping errors low. The work is a lab result about a basic building block, not a working quantum computer.
The findings are described in a RIKEN press release published on 16 October 2026, and in a paper by Yi-Hsien Wu, Leon Camenzind and colleagues in Nature Physics.
Why it matters
Quantum computers store information in qubits. Silicon spin qubits use the spin of single electrons trapped in silicon chips, and are attractive because they could, in principle, be made with techniques similar to those used for ordinary computer chips.
To be useful, a quantum computer needs to operate many qubits at once without errors creeping in. But RIKEN says that sending microwave control signals to several qubits at the same time “can introduce errors that reduce computational accuracy.”
What the team did
The researchers used “a five-qubit silicon array controlled through a single shared microwave line.” They found that the main source of errors during simultaneous operation is the AC Stark shift, an effect of the microwave signals that shifts a qubit’s energy levels and the phase of its quantum state.
To fix it, they developed “a scalable mitigation protocol based on phase calibrations.” “Rather than requiring an entirely separate calibration procedure for every possible combination of qubits, our method uses calibrations between pairs of qubits to compensate for the unwanted phase shifts,” said Yi-Hsien Wu, the first author. Calibrating pairs rather than every combination matters because the number of combinations grows quickly as more qubits are added.
The results
Fidelity measures how accurately a quantum operation is carried out. According to RIKEN:
- One qubit at a time: single-qubit gate fidelities were “well above 99.99%” on each of the five qubits, “with the best approaching 99.999%.”
- Up to three at once: fidelities stayed “above 99.99%.”
- All five at once: fidelities “remained at approximately 99.9%,” which RIKEN calls “a level close to the practical requirements of fault-tolerant quantum computing.”
These are single-qubit gates, operations on individual qubits. The work does not report two-qubit gates, which link qubits together and are also needed for computing.
What still goes wrong
RIKEN says the remaining errors with all five qubits running come from “drive-induced decoherence caused by the increased microwave power needed for simultaneous operation.” Unlike the phase shifts, this is a loss of the qubits’ fragile quantum state, which the new calibration cannot fix.
“This is a limitation, but further improvements to device design could help mitigate this source of error,” said Camenzind, a RIKEN research scientist who supervised the experiments.
The bigger goal
“This shows that high-fidelity control can be maintained even when several qubits are operated at the same time and represents an important step toward scaling up silicon-based quantum processors,” Camenzind said.
“Our long-term goal is to build a fault-tolerant quantum computer based on silicon spin qubits, and reliable parallel control is an essential step toward that goal,” added Seigo Tarucha, who leads a silicon quantum computing project under Japan’s JST Moonshot Goal 6 programme.
What’s still unknown
It is not yet shown whether the method works with many more qubits, or alongside two-qubit gates at similar accuracy. TSN has not read the full paper; the figures above are as reported by RIKEN.
What to watch
Watch for larger silicon arrays, results combining parallel single-qubit and two-qubit gates, and device designs that reduce microwave heating.
What this means
- Parallel control works better. Five qubits ran together at about 99.9% fidelity.
- A known error, tamed. Pairwise phase calibrations fixed the main source of errors.
- Early stage. Single-qubit gates only, on five qubits, in a lab.
Sources
- RIKEN, press release on simultaneous high-fidelity control of silicon spin qubits, 16 October 2026
- Wu, Camenzind et al., “Simultaneous High-Fidelity Single-Qubit Gates in a Spin Qubit Array”, Nature Physics, 2026
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