The energy levels of laterally coupled parabolic double quantum dots are calculated for varying interdot distances. Electron-electron interaction is shown to dominate the spectra: In the diatomic molecule limit of large interdot separation, the two nearly degenerate singlet and triplet ground states are followed by a narrow band of four singlet and four triplet states. The energy spacing between the ground state and the first band of excited states scales directly with the confinement strength of the quantum wells. Similar level separation and band structure are found when the double dot is exposed to a perpendicular magnetic field. Conversely, an electric field parallel to the interdot direction results in a strong level mixing and a narrow transition from a localized state to a covalent diatomic molecular state.

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We investigate the possibility of performing single-electron controlled transport in coupled quantum dots based on magnetic switching. From numerical solution of the time-dependent Schrödinger equation it is shown that certain combinations of static and switched magnetic fields can result in a situation where an initially localized wavefunction can be transferred from one of the dot centres to the other one with unit probability.

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