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Study on optical quantum information processing

光量子信息处理研究

基本信息

批准号：
16204031
负责人：
YAMAMOTO Yoshihisa
金额：
$ 18.8万
依托单位：
National Institute of Informatics
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2007
项目状态：
已结题

项目摘要

Quantum information processing based on weak optical nonlinearity is a promising and practical approach compared to all linear optics quantum information processing, because a required physical resource can be dramatically reduced in this way. In this project we have studied three-level Lamda system provided by donor impurities in semiconductors. A donor impurity in semiconductor captures one un-paired electron at low temperatures and becomes electrically neutral (D^0). Under a dc magnetic field, the bound electron spin states are split by a Zeeman frequency, which constitute a metastable ground states (qubit). Under optical excitation of excitons, the neutral donor captures one exciton and forms a new state, called a donor bound exciton (DoX). The reason why we focused on this system as a source of weak optical nonlinearity is primarily its small inhomogeneous linewidth (~1GHz), which is three-four orders of magnitude smaller than self-assembled quantum dot systems. We mainly studied a donor bound electron/exciton system in GaAs with a density as low as 10^<13> (cm^<-3>). We could demonstrate the coherent population trapping (dark state) experiment, nuclear field induced dephasing effect (T^*_2 ~ few nsec), long T_1 time constant (~4msec), and single Raman pulse induced Rabi oscillation of electron spin states. We have also studied ^<19>F donor impurities in ZnSe matrix and obtained a similar result. These experimental results show that a donor bound electron/ exciton system is a promising candidate as a source of weak optical nonlinearity for quantum information processing.

与全线性光学量子信息处理相比，基于弱光学非线性的量子信息处理是一种有前途和实用的方法，因为这样可以显著减少所需的物理资源。本项目研究了半导体中施主杂质提供的三能级Lamda系统。半导体中的施主杂质在低温下捕获一个未成对电子并成为电中性（D^0）。在直流磁场下，束缚电子自旋态被塞曼频率分裂，构成亚稳基态（量子比特）。在激子的光激发下，中性供体捕获一个激子并形成新的状态，称为供体束缚激子（DoX）。我们之所以关注这个系统作为弱光学非线性的来源，主要是因为它的小的非均匀线宽（~1GHz），比自组装量子点系统小三到四个数量级。我们主要研究了GaAs中的施主束缚电子/激子系统，其密度低至10^<13>（cm^<-3>）。我们可以演示相干布居捕获（暗态）实验、核场诱导的退相效应（T^*_2 ~几纳秒）、长T_1时间常数（~ 4毫秒）和单拉曼脉冲诱导的电子自旋态Rabi振荡。我们还研究了<19>ZnSe基体中的氟施主杂质，得到了类似的结果。这些实验结果表明，施主束缚电子/激子系统是一个很有前途的候选人作为一个源的弱光学非线性量子信息处理。