Five Silicon Qubits Share One Control Line and Keep Their Accuracy

Researchers at the RIKEN Center for Emergent Matter Science and collaborators have driven five silicon spin qubits through one shared microwave line and kept single-qubit operations accurate while several of the qubits ran at the same time.

The paper appeared Oct. 15, 2026, in Nature Physics. Silicon spin qubits hold information in the spin of a single trapped electron and can be made in the same factories as ordinary computer chips. But the authors write that their accuracy normally falls off as soon as several are controlled in parallel, and that operating many qubits accurately at once is a requirement for scaling up a processor.

They found the main cause to be the AC Stark shift: the microwave control signals themselves move a qubit's energy levels and shift the phase of its quantum state. Their remedy calibrates that shift between pairs of qubits, rather than running a separate calibration for every possible combination of them.

Fidelity measures how accurately a quantum operation is performed. The authors report gate fidelities well above 99.99% for each qubit driven on its own, with some approaching 99.999%. With up to three qubits driven at the same time, fidelities stayed above 99.99%. With all five driven in parallel, they remained above 99.9%, the level widely targeted for machines that can correct their own errors.

RIKEN's release attributes the remaining loss during parallel operation to the higher microwave power that driving several qubits at once requires. Leon Camenzind, a research scientist at RIKEN and a co-first author, said in the release: "This is a limitation, but further improvements to device design could help mitigate this source of error."

The paper argues that shared control lines can support the development of large-scale semiconductor quantum processors. RIKEN says Yi-Hsien Wu, the paper's first author, carried out the experiments as part of his PhD research.