Five qubits, one line: RIKEN drives silicon qubits simultaneously
A team at Japan's RIKEN research centre controls five silicon spin qubits through a single shared microwave line – at around 99.9% fidelity even when all of them operate at once.
Archive image · Photo: Kestrel / Wikimedia Commons, CC BY-SA 4.0 (cropped and resized)
Researchers at the RIKEN Center for Emergent Matter Science control five silicon spin qubits through a single shared microwave line. Operated individually, single-qubit gate fidelities are well above 99.99%, with the best qubit approaching 99.999%. The work has been published in Nature Physics.
With up to three qubits running simultaneously, fidelity stays above 99.99% thanks to a new calibration protocol. With all five operating at once it is around 99.9% – close to the practical requirements for fault-tolerant quantum computing. Instead of calibrating every possible combination separately, the team calibrates the qubits in pairs; the main error source was the so-called AC Stark shift.
"This shows that high-fidelity control can be maintained even when several qubits are operated at the same time," says co-first author Leon Camenzind. Remaining losses stem from the higher microwave power needed, but he says improved device design could mitigate them. Project manager Seigo Tarucha names a fault-tolerant quantum computer based on silicon spin qubits as the long-term goal.