All-Optical Quantum Computing with Femtosecond Coherent Control of Excitons in Semiconductor Quantum Dots

*非技术摘要*量子力学的力量将使量子计算机一旦实现，就可以执行远远超出经典计算机能力的任务。破解强加密就是这种任务的一个例子，这是关系到国家安全的一个重要话题。然而，量子信息比经典信息更不稳定，也更难处理，到目前为止，量子计算方法最多只能处理几个量子比特。这一个人研究人员奖支持一项实验研究计划，该计划旨在展示纳米尺寸的半导体量子点中的量子门。量子点由多层半导体制成，其行为就像人造原子，其量子状态可以通过一系列非常快的激光脉冲来控制。该项目将研究量子电路的基本元素。实验将集中在量子点中量子态的最佳控制和测量，挥发性量子信息损失(退相干)的误差率，量子点处理量子信息的最大速度，以及两位门所需的点之间的耦合机制。这项研究将涉及研究生和本科生，因此在超快光学、纳米科学和量子工程等重要领域具有很强的教育意义。这一个人研究人员奖支持一个实验研究计划，该计划探索半导体量子点中激子态的飞秒相干量子控制，作为可扩展量子计算的潜在平台。通过飞秒激光脉冲的傅里叶域脉冲整形得到多色光脉冲序列来控制量子点。该实验计划将研究具有纳秒相干时间的强受限高质量单个和耦合InGaAs和AlGaAs量子点，在退相干发生之前可能允许数千次量子操作。该项目的第一部分将集中于单个量子点，并探索控制和测量其量子态的新方法。这些实验将探索量子操作中退相干的来源，例如激发诱导的极化子晶格失真和声子发射。该项目的第二部分将专注于可伸缩性，旨在演示位于不同量子点中的比特的量子门控。该项目将研究生和本科生的研究和教育融为一体，并在超快光学、纳米科学和量子工程等重要领域提供实践经验。

*****NON-TECHNICAL ABSTRACT*****The power of quantum mechanics will allow quantum computers, once realized, to perform tasks that are well beyond the power of classical computers. An example of such a task is the breaking of strong encryption, an important topic for national security. Quantum information, however, is much more volatile and difficult to handle than classical information, and approaches for quantum computation demonstrated so far can handle a few quantum bits at best. This individual investigator award supports an experimental research program to demonstrate quantum gating in semiconductor quantum dots of nanometer size. Quantum dots are made from layers of semiconductors and behave like artificial atoms whose quantum states can be controlled by sequences of very fast laser pulses. The project will investigate the basic elements for quantum circuits. The experiments will concentrate on optimum control and measurement of the quantum states in quantum dots, the rate of errors from loss of the volatile quantum information (decoherence), the maximum speed with which the dots can process quantum information, and coupling mechanisms between dots necessary for two-bit gates. The research will involve graduate and undergraduate students and therefore have a strong educational component in important fields such as ultrafast optics, nanoscience and quantum engineering.***** TECHNICAL ABSTRACT*****This individual investigator award supports an experimental research program that explores femtosecond coherent quantum control of excitonic states in semiconductor quantum dots as a potential platform for scalable quantum computing. The quantum dots are controlled with multi-color optical pulse sequences derived by Fourier domain pulse shaping of femtosecond laser pulses. The experimental program will investigate strongly confined high-quality single and coupled InGaAs and AlGaAs quantum dots that have nanosecond coherence times, allowing potentially thousands of quantum operations before decoherence occurs. The first part of the project will concentrate on single quantum dots and explore new methods of controlling and measuring their quantum states. The experiments will explore the sources of decoherence during quantum operations, such as excitation-induced polaronic lattice distortion with phonon emission. The second part of the project will concentrate on scalability and aims to demonstrate quantum gating of bits located in separate quantum dots. This project integrates research and education of graduate and undergraduate students, and provides hands-on experience in important fields such as ultrafast optics, nanoscience, and quantum engineering.