Silicon spin qubits reach 99.99% fidelity bringing larger quantum processors into reach.
Researchers working with a five-qubit silicon spin array report gate fidelities above 99.99% for individual qubits and for up to three operated together, using a calibration method that mitigates drive-induced frequency shifts.
Researchers working with a five-qubit silicon spin array report that they kept quantum gate fidelities above 99.99% for each qubit on its own and for up to three qubits running at the same time. The results are described in a research paper.
Silicon spin qubits are regarded as a promising route to scalable quantum computing because they are compatible with industrial semiconductor manufacturing. Building a larger processor requires high-fidelity operations on many qubits in parallel. In silicon devices that has been a major challenge, because fidelities typically fall when several qubits are controlled simultaneously.
The team identified the dominant cause of that decline in their device: a.c.-Stark shifts induced by the microwave drive. To address it, they introduced a mitigation protocol based solely on pairwise phase calibrations, which the authors describe as scalable. They paired it with tailored control pulses delivered over a shared control line.
With this approach, the primitive X and Y gates reached fidelities well above 99.99% for each qubit individually, and some approached 99.999%. Those fidelities stayed above 99.99% when up to three qubits were operated simultaneously.
When all five qubits ran in parallel, fidelities remained above 99.9%. The authors describe that figure as the widely targeted fault-tolerant threshold. The 99.99% level was therefore reported for individual operation and for up to three qubits, not for the full five-qubit case.
The authors conclude that keeping control high-fidelity during simultaneous operation means shared control lines can support the development of large-scale semiconductor quantum processors. The reported work was carried out on a five-qubit array, and the abstract does not give results for larger devices.
Note: The headline implies 99.99% fidelity across the processor. The page reports above 99.99% for individual qubits and for up to three at once, and above 99.9% when all five operated in parallel.
At a Glance
- The device was a five-qubit silicon spin array.
- Microwave-drive-induced a.c.-Stark shifts were identified as the dominant source of fidelity loss in parallel operation.
- Single-qubit X and Y gate fidelities were well above 99.99%, with some approaching 99.999%.
- Fidelities stayed above 99.99% with up to three qubits operating simultaneously.
- Parallel five-qubit operation kept fidelities above the 99.9% fault-tolerant threshold.
Sources
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