The coherent manipulation of a double quantum dot system by an external driving field is analyzed. Using a controlled rotation method a general superposition state of the lower states is formed. Several interaction schemes are discussed and analytic results are presented. These are found to agree very well with the results of numerical simulations.

The donor binding energies associated with the ground state and a few excited states, are computed as a function of the dot size and the impurity position within two and three dimensional GaAs quantum dots. The calculation has been done using the Potential Morphing Method -a recently developed numerical method for the solution of time independent Schrödinger equation. The agreement with both perturbation and variational methods is very good, as regards the dependence of the binding energies on the dot size as well as on the location of the impurity within the quantum dot.Finally, we have shown that this method works well in all confinement limits -from weak to strong confinement.

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In this work we study the potential for coherent manipulation of an asymmetric double quantum dot structure by the use of adiabatic methods. These methods are the Stimulated Raman Adiabatic Passage (STIRAP) and its modification the fractional STIRAP. We show that such a method can be used for complete electron transfer between the two lower states of the quantum dots. In addition, with fractional STIRAP a coherent superposition of the two lower states of the quantum dots can be created.1 Introduction The interaction of electrons confined in double quantum dot structures with electromagnetic driving fields has attracted much attention in the past decade [1][2][3][4]. Several interesting phenomena have been recognized when the quantum dot structure contains one or two electrons. Examples include controlled transfer of electrons between the two quantum dots [1,3] and creation of maximally entangled states in two-electron quantum dot systems [2,4]. These effects are of central interest in the topical area of quantum computation as quantum dots are artificially created structures with potential scalability, so they are one of the most important candidates for realizing solid state quantum computation.In this work we study the potential for coherent manipulation of an asymmetric double quantum dot structure [3,4] by the use of adiabatic methods. These methods are the Stimulated Raman Adiabatic Passage (STIRAP) [5] and its modification the fractional STIRAP [6]. In STIRAP two electromagnetic pulses are applied in the quantum dot structure in a counter-intuitive sequence [5]. These pulses are also partially overlapping. We show that such a method can be used for complete electron transfer between the two lower levels of the quantum dots. In fractional STIRAP, in addition to the previous procedure, the pulses are also switched-off simultaneously [6]. In this case a coherent superposition of the two lower levels of the quantum dots can be created. We note that several studies in the past five years have applied STIRAP and fractional STIRAP for the control of the dynamics of semiconductor nanostructures [7]. The results of the present paper is a direct application of STIRAP in a double quantum dot structure. The results of this paper can be also directly applied to the asymmetric quantum dot structures of Ref. [3].

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