Theory of quantum control of atomic/molecular ensembles by ultrafast electromagnetic fields

量子控制涉及使用定制的电磁场精确操纵量子态的动力学，以达到预期的目标。在最近的实验中，如团簇产生高谐波，以及有机光伏的超快研究，飞秒电磁场被用来驱动、探测或控制原子或分子的集合。这些系综的物理学既不能用少体模型来描述，也不能用整体经典或半经典模型来描述。此外，这些超快光学相互作用都是非线性和非微扰的，这使得它们的理论描述具有挑战性。这一提议探索了量子控制的新前沿，即在超短（几飞秒）时间尺度上控制大量（~5000）原子或分子的密集系综。我们的目标是研究由超快脉冲驱动的密集量子系综的量子动力学，阐明其控制的基本机制，并建立优化控制过程的关键参数。我们将开发和评估量子控制技术，并设计新的协议，以优化现实物理系统中期望的目标，如原子团簇产生高谐波。最终，我们希望我们开发的技术和协议将被超快科学的实验研究人员利用，以更准确地预测和实施控制方案，优化原子和分子过程，如密集系综中的超快散射和高谐波产生。在过去的三年中，我们已经开发了一种理论和计算方法，可以准确地描述量子系综密度范围内的量子动力学，同时在计算成本和时间上是合理的方法。在此基础上，原子团簇中高谐波产生的理论模型，以及描述量子系综中非摄动现象的量子控制所需的数值算法将被开发并在超级计算集群上实现。在NSERC的支持下，我们将在这项工作的基础上开发优化系综所需目标特性的协议，例如，抑制或增强系综脱相或自发发射，或塑造驱动系综发射的辐射光谱。这项工作的新颖之处在于在原子或分子的多体系统中建立了超快量子控制的理论模型，这是一个比以往任何时候都更加复杂的问题。调查线解决了我们对开放控制系统理解的前沿理论/计算问题，与当前和拟议的领先实验有很强的联系。这项发现研究的结果将用于支持我在生物传感器和太阳能电池技术方面的研究项目的应用方面。

Quantum control involves the precise manipulation of the dynamics of quantum states using tailored electromagnetic fields in order to achieve a desired goal. In recent experiments such as high-harmonic generation from clusters, and ultrafast studies of organic photovoltaics, femtosecond electromagnetic fields are used to drive, probe or control ensembles of atoms or molecules. The physics of these ensembles can neither be described by few-body models, nor by bulk classical or semi-classical models. Also, these ultrafast optical interactions are both nonlinear and non-perturbative, making their theoretical description challenging. This proposal explores this new frontier in quantum control, namely, the control of dense ensembles of a large number (~5000) of atoms or molecules over ultrashort (few femtosecond) timescales. Our objectives are to investigate the quantum dynamics of dense quantum ensembles driven by ultrafast pulses, to elucidate the fundamental mechanisms in their control, and to establish the key parameters that optimize the control process. We will develop and evaluate quantum control techniques, and design new protocols for the optimization of desired targets in realistic physical systems such as high-harmonic generation from atomic clusters. Ultimately, we intend that the techniques and protocols that we develop will be exploited by experimental researchers in ultrafast science to more accurately predict and implement control schemes that optimize atomic and molecular processes such as ultrafast scattering and high harmonic generation in dense ensembles. In the past 3 years, we have developed a theoretical and computational methodology that describes the quantum dynamics of quantum ensembles accurately over a range of ensemble densities, while simultaneously being a method that is reasonable in computational cost and time. Building on this, theoretical models of high-harmonic generation in atomic clusters, and numerical algorithms required to describe the quantum control of non-perturbative phenomena in quantum ensembles will be developed and implemented on supercomputing clusters. With NSERC support, we will build on this work to develop protocols for the optimization of desired target properties of the ensemble, for example, to suppress or enhance ensemble dephasing or spontaneous emission, or to shape the spectrum of the radiation emitted from driven ensembles. The novelty of this work is the development of theoretical models of ultrafast quantum control in many-body systems of atoms or molecules, which are problems that are more complex than ever before. The lines of investigation address theoretical/computational problems at the forefront of our understanding of open control systems, with strong ties to current and proposed leading experiments. The results of this discovery research will be used to support the applied aspects of my research program in biosensors and solar cell technology.