Hybrid paramagnetic-ferromagnetic quantum computer design based on electron spin arrays and a ferromagnetic nanostripe.

Designing an assembly of quantum nano-objects which can interact between themselves and be manipulated by external fields, while staying isolated from their noisy environment is the key for the development of future quantum technologies, such as quantum computers and sensors. Electron spins placed in a magnetic field gradient, interacting by dipolar magnetic couplings and manipulated by microwave pulses represent a possible architecture for a quantum computer. Here, a general design for the practical implementation of such nanodevice is presented and illustrated on the example of electron spins in silicon carbide placed nearby a permalloy ferromagnetic nanostripe. Firstly, the confined spin wave resonance spectrum of the nanostripe and the properties of its magnetic field gradient are calculated. Then, one shows how to avoid microwave driven electron spin decoherence. Finally, one shows that decoherence due to ferromagnetic fluctuations is negligible below room temperature for spins placed far enough from the nanostripe