Qubits in quantum dot arrays made with all-optical, 300mm wafer lithography

Spin qubits in gate-defined silicon quantum dots are promising qubit candidates due to their small size and relatively long coherence times. To pave the road towards large-scale quantum computing, making use of common CMOS fabrication techniques, like optical lithography and chemical-mechanical polishing is key. Spin qubit devices to date, however, still rely on the flexibility of e-beam lithography.

Here, we present the first, well-controlled qubits made in quantum dot arrays fabricated in a 300mm process line on an isotopically-enriched 28Si MOS substrate. These devices are fully fabricated with optical lithography and chemical-mechanical polishing techniques for patterning, compatible with state-of-the-art industrial fabrication. We demonstrate well-controlled single and double quantum dots with separate tunnel-barrier control in the multi-electron regime. The latter is a prerequisite to perform high-fidelity two-qubit gates. Moreover, we demonstrate charge sensing with a signal-to-noise ratio high enough for single shot readout. With this, we form high-quality qubits in the single-electron regime, comparable to qubits in academic devices.