Energy levels of the one and two electrons in a Silicon Quantum Dot*

Spin qubits based on electrons confined in silicon quantum dots are promising candidates for universal quantum computation due to their long coherence time and high-fidelity qubit manipulation. The energy levels in a quantum dot are strongly dependent on its size and the coulomb interactions between the electrons. In silicon, the presence of the nearly degenerate valley states provides an additional complexity to the electron spectrum and dynamics. Here we study the effects of the valley-orbit coupling and the change in its value due to interface roughness on the energy spectrum in the spin blockade regime. We have included the valley-orbit coupling in the excited orbital states and studied their impact on the energy levels of a single- and two-electron quantum dot. Our results shed new lights on the controllability and detectability of silicon-based spin qubit for its application in quantum information processing.