太赫兹辅助测量铷原子超快量子相干过程的理论研究  

The theoretical study of terahertz-streaking photoionization for ultrafast imaging of density matrix in rubidium atom

作　　者：凌中火 王帅 张金仓[1] 张逸竹[2,3] 阎天民 江玉海 Ling Zhong-Huo;Wang Shuai;Zhang Jin-Cang;Zhang Yi-Zhu;Yan Tian-Min;Jiang Yu-Hai(Materials Genome Institute,Department of Physics,Shanghai University,Shanghai 200444,China;Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201210,China;Center for Terahertz Waves,College of Precision Instrument and Optoelectronics Engineering,Tianjin University,Tianjin 300072,China;University of Chinese Academy of Sciences,Beijing 100049,China;ShanghaiTech University,Shanghai 201210,China)

机构地区：[1]上海大学物理系,材料基因组工程研究院,上海200444 [2]中国科学院上海高等研究院,上海201210 [3]天津大学精密仪器与光电子工程学院,太赫兹研究中心,天津300072 [4]中国科学院大学,北京100049 [5]上海科技大学,上海201210

出　　处：《物理学报》2020年第17期70-76,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11827806,11874368,61675213)资助的课题.

摘　　要：太赫兹辅助光电离瞬态测量方法可以分辨超快量子拍频,同时对复杂量子系统的超快密度矩阵演化进行成像.本文依据这种方法提出了一种具体的实验方案,利用紫外脉冲(脉宽为30 fs)和高强度太赫兹脉冲(峰值场强:约1 MV/cm)组成复合探测电场,探测铷原子5S1/2和5P3/2叠加态振荡周期约为2.6 fs的量子拍频过程,量子体系密度矩阵演化的布居项和相干项投影在光电子动量谱的不同位置,可以对密度矩阵演化实现完全信息测量.本文设计的实验方案不需要阿秒高次谐波或自由电子激光等复杂的先进光源,可以成为探索复杂量子体系超快相干动力学过程的新方案.Terahertz-streaking photoionization can be exploited to resolve ultrafast quantum beating and reconstruct the ultrafast evolution of density matrix.Here,we propose an experimental strategy to implement the method merely with the tabletop femtosecond system and magneto-optical trap reaction microscopy.The probe pulse consists of an ultraviolet pulse with pulse duration of about 30 fs and a strong terahertz pulse with strength of about 2.6 fs in rubidium-atom superposition.The population and coherence terms of the density matrix can be projected into different positions of the photoelectron momentum distribution.The reconstruction algorithm was designed to acquire the ultrafast evolution of density matrix from the time-dependent photoelectron spectrum.The experimental conception can demonstrate the newly proposed transient spectral method only with the commercial femtosecond laser system and magneto-optical trap reaction microscopy,thus preventing the complex laser system,such as extreme ultraviolet free electron lasers and attosecond higher harmonics,allowing a new metrology to explore the coherence dynamics of quantum systems.

关 键 词：超快量子相干动力学 密度矩阵 量子拍频 太赫兹激光 

分 类 号：O562[理学—原子与分子物理] O441.4[理学—物理]