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Electron spin manipulation in coupled multiple quantum wells for quantum computing

用于量子计算的耦合多量子阱中的电子自旋操纵

基本信息

批准号：
14550001
负责人：
TAKAHASHI Yutaka
金额：
$ 1.6万
依托单位：
YAMAGATA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550001/
关键词：
Quantum Well 2-Dim Electron Gas Spin Transport Spin Relaxation Spin Injection Spintronics Quantum Computing 半導体量子井戸構造結合2重量子井戸

项目摘要

We have studied electron spin properties in semiconductor heterostructures in view of applying it for quantum computing. A very long spin life time is required for achieving practical quantum computing using electron spins as qubits. We have experimentally investigated the spin relaxation of electrons which are photogenerated in bulk GaAs region with circularly polarized pump beam, focusing on which part of the sample the dominant spin relaxation takes place. We have separated electron dynamics in the sample into three stages : (1) Rapid energy relaxation immediately after photogeneration, (2)Field-driven transport in the bulk GaAs region, (3)Electron capture process from the bulk GaAs band edge into the bottom of quantum wells, and we have prepared the sample with two InGaAs quantum wells which work as spin detectors. Our experimental results show that the spin relaxation in stage (1) is small, and the spin relaxation during the transport is strongly dependent on the field strength, when the electric field is kept small, the spin relaxation during transport is very small. The spin relaxation in the capture stage is large, dominating the whole spin relaxation process in our sample. This finding would cause problems since in many proposed spintronics and quantum computing schemes the spin injection into the quantum well is assumed. We are preparing samples with different well width to further investigate the effects of energy levels in quantum wells to the spin relaxations.In order to implement a Controlled-Not gate in quantum computing using spins, adjacent electrons should be coupled with exchange interactions. We proposed a CN gate utilizing the exchange interaction of electrons in coupled 2-dimensional layers. However, out basic study shows that the exchange interaction is very small between the electrons in adjacent layers. We project a plan to study the alternative method using electron spins in quantum dots.

为了将半导体异质结用于量子计算，我们研究了半导体异质结中的电子自旋性质。使用电子自旋作为量子比特来实现实际的量子计算需要很长的自旋寿命。我们实验研究了用圆极化泵浦光束在块体GaAs区产生的电子的自旋弛豫，重点研究了样品的哪一部分发生了主要的自旋弛豫。我们将样品中的电子动力学分为三个阶段：(1)光生后的快速能量弛豫，(2)体相GaAs区的场驱动输运，(3)从体相GaAs体带边到量子阱底部的电子俘获过程，我们用两个InGaAs量子阱作为自旋探测器来制备样品。我们的实验结果表明，(1)阶段的自旋弛豫很小，输运过程中的自旋弛豫强烈依赖于电场强度，当电场较小时，输运过程中的自旋弛豫很小。俘获阶段的自旋弛豫较大，主导了整个自旋弛豫过程。这一发现会带来问题，因为在许多提出的自旋电子学和量子计算方案中，假设自旋注入到量子井中。我们正在制备不同宽度的样品，以进一步研究量子阱中的能级对自旋弛豫的影响。为了在使用自旋的量子计算中实现可控非门，必须将相邻电子与交换相互作用耦合。我们提出了一种利用耦合二维层中电子交换相互作用的CN门。然而，我们的基础研究表明，相邻层中的电子之间的交换作用很小。我们计划研究利用量子点中的电子自旋的替代方法。