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The Influence of the Form Factor on Longitudinal Piezoelectric Acoustic Phonon Decoherence of a Double Quantum Dot Charge Qubit

Author: KangSuYin
Tutor: KongXiaoJun
School: Hebei Normal
Course: Condensed Matter Physics
Keywords: Quantum dot Charge qubit Quality factor Reduced density matrix
CLC: O413
Type: Master's thesis
Year: 2009
Downloads: 26
Quote: 0
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Abstract


A double solid-state quantum dot charge qubit has received a lot of attentions due to its unique properties and a great deal of research work has been done in recent years.In laterally confined double quantum dots,the two electronic ground states separately in the right and left ones may be employed as a two-level quantum system--charge qubit.Based on previous work,we consider the thickness of quantum dots and the different binding potentials for the electron and then study the influence of the interaction between the electron and longitudinal piezoelectric acoustic phonons on decoherence.This paper calculates the quality factor using the reduced density matrix in the Born-Markov approximation.The quality factor can reflect phonon decoherence rates.First of all,the quality factor is calculated in a double cylindrical quantum dot charge qubit.The dependence of the quality factor on the thickness of quantum dots,the tunneling amplitude,lattice temperature,and the radius of quantum dots is discussed.The study finds that the influence of the thickness of quantum dots on phonon decoherence can be ignored for the weak tunneling amplitude.But for the strong tunneling amplitude,the thickness has greater impact on phonon decoherence as the tunneling amplitude increasing.For the larger thickness of quantum dots,the phonon decohenrence rates decrease as the thickness increasing.As for the weak tunneling amplitude,the quality factor may achieve a large value for the strong tunneling amplitude.Therefore,the quantum dots can be considered as two-dimensional model for the weak tunneling amplitude or for the less thickness of quantum dots.If thicker quantum dots are selected in experiment,the thickness should be considered. And selecting thicker quantum dots may effectively supress the interaction between the electron and phonons in experiment.Then,the double quantum dots are regarded as in two-dimensional plane.The quality factor is calculated under considering two-dimensional infinitely deep square potential well for the electron.The study shows that the effect of different binding potentials on phonon decoherence can be neglected for the weak tunneling amplitude.But for the strong one, phonon decohenrence rates will be affected by different binding potential models.Therefore, for the strong tunneling amplitude,different effects which the different binding potential brought need to be considered.

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CLC: > Mathematical sciences and chemical > Physics > Theoretical Physics > Quantum theory
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