电磁场中施主中心量子点内磁极化子态寿命与qubit退相干  

Magnetopolaron-state lifetime and qubit decoherence in donor-center quantum dots with the electromagnetic field

作　　者：白旭芳[1] 陈磊 额尔敦朝鲁[2] Bai Xu-Fang;Chen Lei;Eerdunchaolu(College of Physics and Electronic Information,Inner Mongolia University for Nationalities,Tongliao 028043,China;Institute of Condensed Matter Physics,Hebei Normal University of Science and Technology,Qinhuangdao 066004,China)

机构地区：[1]内蒙古民族大学物理与电子信息学院,通辽028043 [2]河北科技师范学院凝聚态物理研究所,秦皇岛066004

出　　处：《物理学报》2020年第14期236-244,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51902085);内蒙古自治区自然科学基金(批准号:2019MS01011,2019MS06017);河北省自然科学基金(批准号:E2019407123)资助的课题.

摘　　要：采用Lee-Low-Pines变换和Pekar类型变分法推导出非对称高斯势施主中心量子点中磁极化子的基态和激发态能量和波函数,进而构造了qubit所需的二能级结构.基于费米黄金规则研究了磁极化子基态的衰变.通过研究电磁场下材料的介电常数比、电声耦合常数和温度对非对称高斯势施主中心量子点中磁极化子基态寿命的影响,揭示了材料属性与温度、电磁场等环境因素对量子点qubit退相干的影响,进而揭示了体纵光学声子效应导致量子点qubit退相干的机理.Recently,the measurement scheme of quantum dot qubit decocoherence quantized by the longitudinal optical(LO)phonon spontaneous emission rate has attracted the attention and discussion of many researchers.However,it is not difficult to see that the above-mentioned measurement scheme still has some insufficient and imperfect aspects that are to be studied urgently.Considering from the physical mechanism,the essence of the above scheme is to quantify the decoherence time of qubit by using the excited state decay time or excited state lifetime of the polaron.However,so far,there is little research on how the ground state decay time and ground state lifetime of two-state polaron affect the coherence of qubit.There is no doubt that this is an equally important research topic.This is because,firstly,for the coherence of the quantum state of polaron,both the decay of the excited state and the decay of the ground state will destroy or attenuate the qubit coherence,secondly,the transition rate of the two-state polaron from the ground state to the excited state after absorbing an LO phonon is also a function quantifying the qubit decoherence time of two-state system of which the inverse is called the ground state decay time or the ground state lifetime.It may be called a measure of qubit decoherence time quantized by the ground state decay time or ground state lifetime of polaron.In this article,the ground-state and excited-state energy and wave function of the magnetopolaron in a donor-center quantum dot with asymmetric Gaussian potential are derived by Lee-Low-Pines transformation and Pekar-type variational methodd,and then the two-level structure for a qubit is constructed.The measure of qubit decoherence time of quantum dots quantified by ground state decay time of two-state polaron is established,which is compared with the well-known measure of qubit decoherence time of quantum dots quantified by polaron excited state decay time,and their physical mechanisms are revealed.By studying the influence of dielectric constant

关 键 词：施主中心量子点 非对称高斯势 磁极化子 寿命 退相干 

分 类 号：O471.1[理学—半导体物理]