Quantum transport simulation of spin qubits in double quantum dots formed at zigzag edges of strained graphene nanoribbons

We propose a spin qubit device based on a strained graphene nanoribbon with zigzag edges. Spin-dependent quantum transport simulations are performed using the non-equilibrium Green's function method, demonstrating that strain induces double quantum dots at the ribbon edges. The strain generates barrier-like potentials along the edges, leading to the localization of spin qubits within the double dots. We evaluate the controllability of the exchange interaction between localized spins via side gate voltages, and find that steep switching of the interaction is achievable. The device architecture enables operation near a flat minimum of the exchange coupling, enhancing robustness against electrical noise. Consequently, a noise-resistant SWAP gate can be realized, with a fidelity comparable to the threshold required for quantum error correction. Our results highlight the potential of strain-engineered graphene nanoribbons for scalable spin-based quantum computing.