Optically Driven Both Classical and Quantum Unary, Binary, and Ternary Logic Gates on Co-Decorated Graphene Nanoflakes

Nanospintronics holds great potential for providing high-speed, low-power, and high-density logic and memory elements in future computational devices. Here, using ab initio many-body theory, we suggest a nanoscale framework for building quantum computation elements, based on individual magnetic atoms deposited on graphene nanoflakes. We show the great possibilities of this proposal by exemplarily presenting four quantum gates, namely, the unary Pauli-X, Pauli-Y, Pauli-Z, and Hadamard gates, as well as the universal classical ternary Toffoli gate, which preserves information entropy and is therefore fully reversible and minimally energy consuming. All our gates operate within the subpicosecond time scale and reach fidelities well above 90%. We demonstrate the ability to control the spin direction and localization, as well as to create superposition states and to control the quantum phase of states, which are indispensable ingredients of quantum computers. Additionally, being optically driven, their predicted operating speed by far beats that of modern quantum computers.

Automated summary

Nanospintronics has the potential to provide high-speed, low-power, and high-density logic and memory elements for future computational devices. A nanoscale framework for building quantum computation elements based on individual magnetic atoms deposited on graphene nanoflakes is proposed using ab initio many-body theory. The proposal demonstrates the possibilities of constructing four quantum gates and a universal classical ternary Toffoli gate with subpicosecond operation time and fidelities above 90%. The ability to control spin direction and localization, create superposition states, and control quantum phase is shown, along with the significantly higher operating speed compared to modern quantum computers due to optical driving.