High-Fidelity N-qubit Quantum Controlled-Not Gates on Quantum-Dot Spins

Realizing high-fidelity n -qubit quantum controlled-not gates is of critical significance. Applying quantum-dot (QD) spins as qubits, an ( n − 1)-qubit control 1-qubit not gate and a 1-qubit control ( n − 1)-qubit not gate is constructed. By utilizing the balanced condition, even under the condition of weak coupling, the circuit including the wave-form correctors and the balanced reflection condition of the cavity may effectively reduce the noise resulting from the unequal reflectance, so that the fidelity of each quantum gate operation can be increased to unity in theory. The operational complexity is further reduced, considering that low-Q cavities are used. In addition, the control gate of m -qubit control ( n − m )-qubit can also be performed with a similar device diagram, only by changing the numbers of the control qubits and target qubits. These n -qubit controlled-not gates can help construct simpler quantum computing circuits that can be widely applied in quantum information processing.