Shared Microwave Control Keeps Silicon Qubits Accurate
Researchers at RIKEN and collaborators demonstrated parallel control of five silicon spin qubits using one shared microwave line. They traced a key control-error source and created a calibration method that preserved high gate fidelity, with individual qubits exceeding 99.99% and up to three simultaneous qubits staying above that level. When all five operated together, fidelity was about 99.9%, suggesting a route toward scalable silicon quantum processors.
Silicon spin qubits store quantum information in the spin of an electron confined within silicon. Because microwave pulses steer these spins, operating many qubits together demands precise, parallel control. The RIKEN team and collaborators used one shared microwave line for five such qubits and reported in Nature Physics that individual gate fidelities exceeded 99.99%, with the best nearing 99.999%.
They linked a main parallel-control error to the AC Stark shift, which alters a qubit’s effective energy levels and phase. Instead of calibrating every possible qubit combination, their protocol used pairwise calibrations. Three simultaneous qubits stayed above 99.99%, while all five together reached about 99.9%, supporting shared control lines as a possible scaling route.
If shared microwave control proves scalable, it could affect quantum researchers and semiconductor manufacturers by aligning larger silicon quantum processors with established chipmaking methods. That may lower barriers to building more capable machines, potentially benefiting fields that rely on complex computation. Real-world impact would depend on further engineering, error correction, and whether the approach holds as qubit counts grow.