Spin Echoes and Coherent Nonlinear Optics in Semiconductors

****非技术摘要****电子的特征在于它们的自旋和电荷性质。电子可以通过自旋产生磁场并与之相互作用。通过利用电子的自旋特性，人们可以开发出量子计算机，它可以比现有的任何经典计算机更快地解决某些问题。这个个人研究项目研究电子自旋如何与半导体中周围的核自旋相互作用。实验研究将基于使用持续时间为几皮秒的激光脉冲。由于电子和核自旋之间的相互作用可以阻止量子计算机中电子自旋的正常功能，因此该项目的主要目标是使用超快激光脉冲将电子自旋与周围的核自旋解耦或隔离。本课程的研究将为研究生和本科生提供半导体物理、纳米技术和信息科学与技术方面的优秀培训，为他们在学术界、工业界或政府部门的职业生涯做好准备。该项目得到了材料研究部和物理部的支持。****技术摘要****这个个人研究项目旨在提高我们控制半导体中电子自旋的基本退相干过程的能力。该项目将研究半导体中局域电子和二维电子气体的光学自旋回波和相干非线性光学过程。高纯n型砷化镓中的供体束缚电子和调制掺杂CdTe量子阱中的电子气体将分别作为局域电子和二维电子气体的模型系统。电子自旋与周围核自旋池耦合产生的自旋退相干将通过光学自旋回波进行研究，并特别强调对非马尔可夫自旋退相干过程的理解。由于核自旋槽的耦合而丢失的自旋相干性的恢复将用动态解耦技术进行探讨。多体库仑相互作用如何从根本上改变二维电子气体中的相干光学过程的问题将通过双脉冲和三脉冲微分吸收技术来解决。在这个项目中进行的研究为半导体物理、纳米技术和量子信息的研究生和本科生提供培训。该项目得到了材料研究部和物理部的支持。

****NON-TECHNICAL ABSTRACT****Electrons are characterized by their spin as well as charge properties. An electron can generate and interact with a magnetic field through its spin. By taking advantage of spin properties of electrons, one can develop quantum computers that can solve certain problems much faster than any of current classical computers. This individual investigator project studies how electron spins interact with the surrounding nuclear spins in a semiconductor. Experimental studies will be based on the use of laser pulses with durations of order picoseconds. Since interactions between electron and nuclear spins can prevent the proper function of electron spins in a quantum computer, a primary objective of this project is to decouple or isolate electron spins from the surrounding nuclear spins with the use of ultrafast laser pulses. Research conducted in this program will provide excellent training for graduate and undergraduate students in semiconductor physics, nanotechnology, and information science and technology, preparing them for careers in academe, industry, or government. The project receives support from the Divisions of Materials Research and Physics.**** TECHNICAL ABSTRACT****This individual investigator project seeks to advance our ability to control fundamental decoherence processes of electron spins in semiconductors. The project will study optical spin echoes and coherent nonlinear optical processes of localized electrons and two-dimensional electron gas in semiconductors. Donor bound electrons in high purity n-type GaAs and electron gas in modulation doped CdTe quantum wells will be used as model systems of localized electrons and two-dimensional electron gas, respectively. Spin decoherence arising from the coupling of an electron spin to the surrounding nuclear spin bath will be investigated with optical spin echoes and with a particular emphasis on the understanding of non-Markovian spin decoherence processes. Restoration of spin coherence lost due to the coupling to the nuclear spin bath will be explored with dynamical decoupling techniques. The issue of how many-body Coulomb interactions fundamentally modify coherent optical processes in a two-dimensional electron gas will be addressed with both two-pulse and three-pulse differential absorption techniques. Research conducted in this program provides training for graduate and undergraduate students in semiconductor physics, nanotechnology, and quantum information. The project receives support from the Divisions of Materials Research and Physics.