Geometric control of concurrence and quantum gate operations in triangular triple quantum dots

As an important index to measure the degree of entanglement in quantum systems, concurrence plays an important role in practical research. In this paper, we study the concurrence between two qubits in triangular triple quantum dot structure. Through calculation and simulation, it is found that concurrence is mainly affected by the interdot coupling strength t, Coulomb interaction U, temperature T, and electrode coupling Γ. Through comparative studies with parallel triple quantum dot structures, we demonstrate that the triangular geometry exhibits significantly enhanced concurrence under identical conditions. In addition, under the condition that concurrence exceeds 0.9, the functional relationship between t and U is obtained through simulation, which provides theoretical support for quantum dot regulation under high entanglement. Finally, we demonstrate the feasibility of implementing a three-qubit quantum gate, using the Toffoli gate as a representative example, under the condition that the triangular triple quantum dot system maintains high entanglement.