Scientists at RIKEN have achieved an important step forward in controlling silicon qubits. They managed to maintain high operation fidelity when several qubits operate simultaneously through a single shared microwave control line.
The researchers worked with five silicon spin qubits. They identified a key source of control errors and developed a calibration protocol that compensates for them. The results were published in Nature Physics.
When tested individually, the fidelity of single-qubit operations exceeded 99,99%, and in the best cases approached 99,999%. With the new protocol, this level was maintained during the simultaneous operation of up to three qubits.
When all five qubits operated together, the fidelity remained around 99,9% — close to the requirements of fault-tolerant quantum computing. "This shows that high-fidelity control can be maintained even when several qubits operate simultaneously and represents an important step toward scaling silicon quantum processors," noted Leon Camenzind, a research fellow at RIKEN and co-author of the study.
The silicon platform is attractive because it relies on already well-established chip manufacturing technologies. The success with parallel control through a single line reduces the complexity of scaling and brings the practical use of such systems closer.
How far it will be possible to advance further will be shown by the next series of experiments, but the current result already changes the understanding of the capabilities of silicon qubits.
