Spin Echoes and Coherent Nonlinear Optics in Semiconductors

*非技术摘要*电子的特征是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，人们可以开发出比目前任何经典计算机都能更快地解决某些问题的量子计算机。这个单独的研究项目研究半导体中的电子自旋如何与周围的核自旋相互作用。实验研究将以使用持续时间为皮秒量级的激光脉冲为基础。由于电子自旋和核自旋之间的相互作用可能会阻碍量子计算机中电子自旋的正常功能，该项目的一个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。该项目开展的研究将为半导体物理、纳米技术和信息科学与技术方面的研究生和本科生提供出色的培训，为他们在学术界、行业或政府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*这个单独的研究人员项目寻求提高我们控制半导体中电子自旋的基本消相干过程的能力。该项目将研究半导体中定域电子和二维电子气的光学自旋回波和相干非线性光学过程。高纯n型GaAs中的施主束缚电子和调制掺杂的CdTe量子阱中的电子气将分别作为定域电子和二维电子气的模型系统。由电子自旋与周围核自旋池的耦合引起的自旋退相干将用光学自旋回波来研究，并特别强调对非马尔科夫自旋退相干过程的理解。我们将用动态去耦合技术来探索由于耦合到核自旋池而造成的自旋相干损失的恢复。我们将用双脉冲和三脉冲差分吸收技术来解决从根本上改变二维电子气中相干光学过程的多体库仑相互作用的问题。该项目的研究为研究生和本科生提供半导体物理、纳米技术和量子信息方面的培训。该项目得到了材料研究和物理系的支持。

****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.