Energy efficient control of semiconductor spin qubits with nanoscale magnets

Conventional electron spin resonance (ESR) [1,2] drive of semiconductor spin qubits relies on generating an oscillating Oersted field that requires substantial power, and limits scalability. Here, we show that an oscillating stray field generated by a nanoscale magnet, whose magnetization is driven by spin-orbit torque, can be at least an order of magnitude more energy efficient than conventional ESR drive, while potentially being more robust (higher coherence times) than spin qubits driven by electric dipole spin resonance (EDSR) [3-5] which are susceptible to charge noise. Our simulations show that by applying relatively smaller RF currents than ESR drive to a heavy metal layer (Pt/W) at the ferromagnetic resonance frequency of Co nanomagnets deposited on top, the spin-orbit torque on the Co nanomagnets can drive their magnetization to large oscillations. We propose high-speed energy-efficient gating of spin qubits using stray field of nanomagnets as a scalable alternative to conventional spin rotation mechanisms.