Strong correlation effects in a capacitively coupled double quantum-dot setup were previously shown to provide the possibility of both entangling spin-charge degrees of freedom and realizing efficient spin-filtering operations by static gate-voltage manipulations. Motivated by the use of such a device for quantum computing, we study the influence of electromagnetic noise on a general spin-orbital Kondo model and investigate the conditions for observing coherent, unitary transport crucial to warrant efficient spin manipulations. We find a rich phase diagram where low-energy properties sensitively depend on the impedance of the external environment and geometric parameters of the system. Relevant energy scales related to the Kondo temperature are also computed in a renormalization-group treatment, allowing us to assess the robustness of the device against environmental effects. These are minimized at low bias voltage and for highly symmetric devices concerning the geometry.

• Received 8 August 2007

DOI:https://doi.org/10.1103/PhysRevB.77.045309