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

Abstract

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 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, I show how to avoid microwave driven electron spin decoherence. Then, I show that at temperatures requiring only nitrogen gaz cooling, the silicon vacancy decoherence process due to ferromagnetic fluctuations is negligible compared to the one due to a two phonons Raman process, as long as the silicon vacancies spins are placed far enough from the ferromagnetic nanostripe. I then show that a nitrogen cooled hybrid quantum processor with 32 silicon vacancies spins qubits in SiC is theoretically possible. NV centers in diamond, N@C60 molecules, and radical molecules are three other good spin qubits candidates for implementing this hybrid quantum processor.