A Valley Hot-Spot Driven Singlet-Triplet Qubit in a Silicon MOS DQD*

Electron spins in silicon quantum dots (QDs) have gained traction as a promising qubit platform due to the controllability of qubit-qubit interactions and the availability of mature silicon microelectronics fabrication techniques. However, confining electrons to QDs at the Si/SiO₂ interface has recently been shown to produce stronger than expected spin-orbit (SO) physics. Here, we present a novel operating mode of a singlet-triplet qubit that exploits an inter-valley SO interaction to drive high-orthogonality, electrical-only qubit control. We employ this interaction to produce a high-performance qubit with operational S-T₀ rotation frequencies exceeding 200 MHz and a quality factor, Q = f x T₂^*, near 20. Utilizing SO effects to drive qubits offers the advantage of all-electrical control, avoiding the need for micromagnets or on-chip microwave strip-lines, and allows for a characterization of the MOS platform without the added fabrication complexity of additional nano-fabricated metal layers.