Fidelity of Optically Controlled Single- and Two-Qubit Operations on Coulomb-Coupled Quantum Dots

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We investigate the effect of the Coulomb interaction on the applicability of quantum gates on a system of two Coulomb-coupled quantum dots. We calculate the fidelity for a single- and a two-qubit gate and the creation of Bell states in the system. The influence of radiative damping is also studied. We find that the application of quantum gates based on the Coulomb interaction leads to significant input state-dependent errors which strongly depend on the Coulomb coupling strength. By optimizing the Coulomb matrix elements via the material and the external field parameters, error rates in the range of 10⁻³ can be reached. Radiative dephasing is a more serious problem and typically leads to larger errors on the order of 10⁻² for the considered gates. In the specific case of the generation of a maximally entangled Bell state, error rates in the range of 10⁻³ can be achieved even in the presence of radiative dephasing.