Towards deciphering the optimal field - system interaction in femtosecond adaptive control of molecular dynamics

光脉冲的整形与反馈相结合以改变其形状以获得最佳结果，为控制分子提供了一个实验旋钮。这种控制可以导致反应产率的提高，这是其他方法不可能实现的。研究包括三个方面：(1)确定控制三原子系统(如CO2)三个基本振动模的最佳光脉冲；(2)测量光脉冲的光谱和时间特性，得到预期的结果；(3)从理论上理解光脉冲与分子系统的相互作用。在将要进行的一系列实验中，将通过所谓的“自适应”反馈获得形状最佳的光脉冲(持续时间以飞秒为单位)。在与光脉冲相互作用之后，分子系统的最新成像通过运行遗传或进化算法的计算机来引起对下一个光脉冲的改变，该遗传或进化算法“学习”如何改变光脉冲的每种模式的幅度，以获得更接近期望的结果。这项工作的结果可能有助于分子控制领域的变革，因为它们的影响将超出待研究的小系统。这种方法可以用于从更大的系统中提取与分子间和分子内运动和动力学相关的重要信息。控制分子振动模式的努力将是能够使用光谱中红外范围的超短成形光脉冲来创建和操纵分子量子比特的关键之一。量子比特类似于传统计算机的比特，是量子计算机的基本单位，量子计算机是一种潜在的强大计算机器，科学家们还不知道如何建造它。这项工作可能有助于更好地理解这一问题的一种可能的解决方案。最后，这项工作的结果可以为环境管理和国家安全关切的问题提供新的方法。该项目正在马里兰大学实施，将成为研究生和本科生以及博士后的培训基地。该项目的跨学科性质涉及具有物理、化学和工程背景的学生。正在进行一项特别的努力，以吸引代表不足的群体的调查人员加入我们的计划。

The shaping of light pulses coupled with feedback to alter their shape for optimum results, provides an experimental knob to control molecules. Such control can lead to improvement of the yield of a reaction in a way that is not possible by other means. The research has three aspects: (1) determining the optimal light pulse to control the three fundamental vibrational modes of a 3-atom system (e.g., CO2), (2) measuring the spectrum and time characteristics of the light pulse which gives the desired results, and (3) understanding theoretically the interaction between the light pulse and the molecular system. In the series of experiments to be done, the optimally shaped light pulses (with durations measured in femtoseconds) will be obtained via so called "adaptive" feedback. State-of-the-art imaging of the molecular system following interaction with a light pulse causes changes to the next light pulse via a computer running genetic or evolutionary algorithms which "learn" how to alter the amplitude of each mode of the light pulse to obtain a result closer to that which is desired. This process continues until the desired outcome is achieved.The results of this work may contribute to transforming the field of molecular control because they will have an impact beyond the small systems to be studied. The approach could be used for extracting important information associated with inter- and intra-molecular motion and dynamics from much larger systems. Efforts to control vibrational modes of molecules will be one key to enabling the use of ultra-short, shaped pulses of light in the mid infrared range of the spectrum for the creation and manipulation of molecular qubits. A qubit, analogous to the bit of a conventional computer, is the fundamental unit of "quantum computer", which is a potentially powerful computing machine which scientists do not yet know how to build. This work may contribute to better understanding of one possible solution to this problem. Finally, the results of this work could enable new approaches to problems of concern to environmental stewardship and National Security. This project is being carried out at the University of Maryland and will be a training ground for graduate and undergraduate students as well as postdocs. The cross disciplinary nature of the program involves students with physics, chemistry and engineering backgrounds. A special effort is being made to attract investigators from underrepresented groups into our program.