Radio-frequency cascade readout of coupled spin qubits fabricated using a 300~mm wafer process (2408.01241v4)

Abstract: Advanced semiconductor manufacturing offers a promising path to scaling up silicon-based quantum processors by improving yield, uniformity, and integration. Individual spin qubit control and readout have been demonstrated in quantum dots fabricated on 300 mm wafer metal-oxide-semiconductor (MOS) processes, yet quantum processors require two-qubit interactions to operate. Here, we use a 300 mm natural silicon MOS process customised for spin qubits and demonstrate coherent control of two electron spins using the exchange interaction, forming the basis for entangling gates such as $\sqrt{\text{SWAP}}$. We measure gate dephasing times of up to $T_2^{*}\approx500$ ns with a quality factor of 10. For readout, we introduce a novel dispersive readout technique, the radio-frequency electron cascade, that simplifies the qubit unit cell while providing high gain. This method achieves a signal-to-noise ratio of 6 within an integration time of 46 ${\mu}$s, the highest-performing dispersive readout demonstration in a planar MOS process. The combination of sensitive dispersive readout with industrial-grade manufacturing marks a crucial step towards large-scale integration of silicon quantum processors.