Five silicon spin qubits controlled at once over a shared microwave line
A team from RIKEN, National Taiwan University, ETH Zurich and TU Delft controlled five silicon spin qubits (physical) simultaneously over a shared microwave line, in a study published in Nature Physics, according to Quantum Computing Report. Individually, pi/2 gate fidelities were well above 99.99%, in some cases approaching 99.999%, per the study abstract. With up to three qubits driven at once (250 nanosecond pulses) fidelities stayed above 99.99%, and with all five in parallel (250 and 500 nanoseconds) they reached 99.9%, which the authors describe as a practical threshold for error tolerance. The main accuracy loss was attributed to an AC Stark shift, and first author Yi-Hsien Wu said the mitigation method calibrates between qubit pairs rather than every possible combination.