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Abstract
A numerical tool is developed to calculate the exciton energy and oscillator strength in newly emerged typeII nanowire quantumdots. For a singlequantumdot, the poor overlap of the electron part and the weakly conﬁned hole part of the exciton wavefunction leads to a small oscillator strength compared to typeI systems. To increase the oscillator strength, we propose a doublequantumdot structure featuring a strongly localized exciton wavefunction and a corresponding fourfold relative enhancement of the oscillator strength, paving the way towards eﬃcient optically controlled quantum gate applications in the typeII nanowire system. Next, an optical gating scheme for quantum computing based on typeII doublequantumdots is proposed. The qubit is encoded on the electron spin and the gate operations are performed by stimulated Raman adiabatic passage (STIRAP) using the position degree of freedom in doublequantumdots to form an auxiliary groundstate. Successful STIRAP gating processes require an eﬃcient coupling of both qubit groundstates of the doublequantumdot to the gating auxiliary state and we demonstrate that this can be achieved using a charged exciton state. Crucially, by using typeII quantumdots, the hole is localized between the two spatially separated electrons in the chargedexciton complex, thereby eﬃciently coupling the electron states orbitals. We subsequently exploit the scheme to realize single and twoqubit gates for quantum computation. The conditional operation is performed by using Coulomb coupling to induce a shift of the STIRAP transition frequencies leading to a conditional violation of the STIRAP twophoton resonance. We calculate the ﬁdelity of gates and show their performance is robust against the spin and charge noises.
Original language  English 

Publisher  Technical University of Denmark 

Number of pages  147 
Publication status  Published  2018 
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 1 Finished

Singlephoton quantum information technology
Taherkhani, M., Gregersen, N., Mork, J., Jauho, A., McCutcheon, D., Marquardt, O. & Zinner, N. T.
15/05/2015 → 05/09/2018
Project: PhD