Buried nanomagnet realizing high-speed/low-variability silicon spin qubits: implementable in error-correctable large-scale quantum computers

We propose a buried nanomagnet (BNM) realizing highspeed/low-variability silicon spin qubit operation, inspired by buried wiring technology, for the first time. High-speed quantum-gate operation results from large slanting magnetic-field generated by the BNM disposed quite close to a spin qubit, and low-variation of fidelity thanks to the self-aligned fabrication process. Employing TCAD-based simulation, we demonstrate that the BNM realizes 10 times faster Rabi oscillation (faster spin-flip) than previous works and >99% fidelity under certain process variations. Also, the proposed BNM arrangement is implementable for error-correctable large-scale quantum computers employing a 2D-latticed qubit layout. This technology paves the way to practical large-scale quantum computers with silicon.