Electron Dynamics in AC-Driven Quantum Dots

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We investigate the dynamics of interacting electrons confined to two types of quantum dot system, when driven by an external AC field. We first consider a system of two electrons confined to a pair of coupled quantum dots by using an effective two-site model of Hubbard-type. Numerically integrating the Schroedinger equation in time reveals that for certain values of the strength and frequency of the field the tunneling between the dots can be destroyed, thus allowing the correlated two-electron states to be manipulated. We then show how Floquet theory can be used to predict the field parameters at which this effect occurs. We then consider the case of confining the electrons to a single two-dimensional quantum dot in the limit of low particle-density. In this system the electrons form strongly correlated states termed Wigner molecules, in which the Coulomb interaction causes them to become highly localised in space. Again using an effective model of Hubbard-type, we investigate how the AC field can drive the dynamics of the Wigner states. As before, we find that the AC field can be used to control the tunneling between various charge configurations, and we relate this to the presence of avoided crossings in the Floquet quasi-energy spectrum. These results hold out the exciting possibility of using AC fields to control the time evolution of entangled states in mesoscopic devices, which has great relevance to the rapidly advancing field of quantum information processing.