Electrically tunable spin qubits in strain-engineered graphene p - n junctions

Strain engineering enables quantum confinement in pristine graphene without degrading its intrinsic mobility and spin coherence. Here, we extend previously proposed strain-induced charge-qubit architectures by incorporating spin degrees of freedom through Rashba spin-orbit coupling and Zeeman fields, enabling spin-qubit operation in single-layer graphene. In a graphene p-n junction, a strain-induced nanobubble generates a pseudomagnetic field that forms double quantum dots with gate-tunable level hybridization. Tight-binding quantum transport simulations and a four-band model reveal two distinct avoided crossings: spin-conserving gaps at zero detuning and spin-flip gaps at finite detuning, the latter increasing with spin-orbit coupling strength while the former decreases. Time-domain simulations confirm detuning-dependent Rabi oscillations corresponding to these two operational regimes. These results demonstrate that strain-induced confinement combined with tunable spin-orbit coupling provides a viable mechanism for coherent spin manipulation in pristine graphene, positioning strained single-layer graphene as a promising platform for scalable spin-based quantum technologies.