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Journal of Physics Condensed Matter

Electron transport in a double quantum dot controlled by magnetic switching

V. Popsueva, Morten Førre, J. P. Hansen, L Kocbach

Published Apr 18, 2007• 4 citations
Publisher

Abstract

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.

DOI
10.1088/0953-8984/19/19/196204

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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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Abstract We studied the dynamics of a pair of single-electron double quantum dots (DQDs) under longitudinal and transverse static magnetic fields and time-dependent harmonic modulation of their interaction couplings. We propose to modulate the tunnel coupling between the QDs to produce one-qubit gates and the exchange coupling between DQDs to generate entangling gates, the set of operations required for quantum computing. We developed analytical approximations to set the conditions to control the qubits and applied them to numerical calculations to test the accuracy and robustness of the analytical model. The results shows that the unitary evolution of the two-electron state performs the designed operations even under conditions shifted from the ideal ones.
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We theoretically investigate the coherent transfer of one electron between the ground states of a double coupled quantum dot structure. The coherent transfer of the electron is externally controlled by applied electromagnetic fields with on- or close-resonance driving frequencies and various shapes and duration. We derive the analytical expressions for the parameters of the external fields by approximating the quantum dot system as a three-level Λ-type system. The analytical solutions are compared with numerical results and good agreement is found. The control methods developed here are applicable in symmetric and asymmetric quantum dot nanostructures.
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A single electron spin in a double quantum dot in a magnetic field is considered in terms of a four-level system. By describing the electron motion between the potential minima via spin-conserving tunneling and spin flip caused by a spin–orbit coupling, we inversely engineer faster-than-adiabatic state manipulation operations based on the geometry of four-dimensional rotations. In particular, we show how to transport a qubit among the quantum dots performing simultaneously required spin rotations.