NSF: Templated Ordered Endohedral Fullerenes as Building Blocks for Quantum Computing

由纳米颗粒组成的复合材料结合在有机基质中，提供了多种可能的应用，从增韧聚合物到化妆品和防晒霜。一些有机材料固有的自组装成更大结构的能力，特别是嵌段共聚物，可以用来实现定义良好和可调的形态。我们打算利用这种控制来实现有机基质内嵌富勒烯物种的分层排序。如果嵌入的纳米结构具有足够明确和强大的量子特性，它们可能能够存储和处理量子信息，从而在基础水平上提供超越经典计算的前景。在我们的结构中实现一个基本的量子逻辑门将需要控制富勒烯之间的相互作用，这反过来又取决于它们在有机矩阵中的排列，因此是对我们项目成功的严格考验。我们建议在控制聚合物纳米复合材料的层次形态的一般背景下，通过利用有机基质中的自组装，实现具有明确形态的自旋活性富勒烯物种的可控排列。为了达到这个目的，我们将使用嵌段共聚物、环糊精和杯芳烃。嵌段共聚物具有明确的纳米相行为，这已经导致它们在通过光刻模板制造纳米图案方面的应用。它们也被研究为能够排序纳米颗粒内含物的系统。为了实现富勒烯的可控排列，它们必须完全集成到基体材料的自组装结构中。我们将采用两种方法：第一种方法是将富勒烯分离成一个确定的相，就像嵌段共聚物中经常出现的那样。第二种方法是将富勒烯二聚体封装在更小的有机单元中，如双环糊精和双杯芳烃，这些有机单元随后会自组装成有序的结构。我们将使用一系列技术来评估这些技术的发展，包括核磁共振（NMR）和低压（LV）和高分辨率（HR）透射电子显微镜（TEM），以及自旋活性富勒烯二聚体分子作为定位探针的电子自旋共振（ESR）。一旦我们的对准策略得到优化，我们将通过使用它来展示相互作用的自旋系统的相干操纵，来展示我们在所得纳米复合材料中实现的精细控制。某些内嵌富勒烯内的电子自旋是量子信息的理想表现，因为它具有极强的鲁棒性和精确操纵的能力。这样的自旋之间的偶极相互作用可以用来证明基本的概念，如纠缠，以及自旋之间的受控非操作。这种相互作用取决于自旋对相对于外加场的方向。使用不对称的富勒烯二聚体，每个富勒烯单元中都有一个可单独寻址的电子自旋，我们将完全控制两个耦合电子/核自旋对的系统，能够包含多达四个或更多量子比特（量子位）。我们打算演示电子自旋之间的量子纠缠，因此一个简单的量子计算，如Deutsch-Josza算法。最后，我们将尝试用寿命较长的核自旋进行同样的演示，在这种情况下，使用电子自旋来分配纠缠。这项雄心勃勃的实验对我们制造功能纳米复合材料定向阵列的能力提出了强烈的要求，从而形成了我们新技术的引人注目的演示。

Composite materials consisting of nanoparticles incorporated within organic matrices offer a diverse range of possible applications, from toughened polymers to cosmetics and sun screens. The inherent ability of some organic materials to self-assemble into larger structures, in particular block copolymers, can be used to achieve well-defined and tuneable morphologies. We intend to exploit this control to achieve hierarchical ordering of endohedral fullerene species within an organic matrix. If the embedded nanostructures have sufficiently well-defined and robust quantum properties, they may be capable of storing and processing quantum information, thus offering the prospect of outperforming classical computation at a fundamental level. The implementation of a basic quantum logic gate in our structures will require control of the interactions between fullerenes, which in turn depend on their alignment within the organic matrix, and thus serves as a demanding test of the success of our project. We propose to achieve controlled alignment of spin-active fullerene species with well defined morphologies, by exploiting self-assembly in organic matrices, within the general context of controlling the hierarchical morphology of polymer nanocomposites. To achieve this, we shall use block copolymers, cyclodextrins and calixarenes. Block copolymers have well-defined nanophase behaviour which has already led to their use in fabricating nanopatterns by lithographic templates. They are also being investigated as systems capable of ordering nanoparticulate inclusions. To achieve controlled alignment of the fullerenes, it is essential that they become fully integrated into the self-assembled structure of the matrix material. We shall follow two approaches: the first is engineering a segregation of the fullerenes into a defined phase, as are often present in block copolymers. The second is to encapsulate fullerene dimers within smaller organic units such as bis-cyclodextrins and bis-calixarenes, which subsequently self-assemble into ordered structures. We shall use a range of techniques to evaluate the development of these techniques, including nuclear magnetic resonance (NMR) and low-voltage (LV) and high resolution (HR) transmission electron microscopy (TEM), and electron spin resonance (ESR) of spin active fullerene dimer molecules acting as alignment probes. Once our alignment strategy has been optimised, we shall demonstrate the exquisite control we have achieved in the resulting nanocomposite by using it to show coherent manipulation of interacting spin systems. The electron spin within certain endohedral fullerenes is an ideal manifestation of quantum information, due to its extremely robust nature and ability to be accurately manipulated. The dipolar interaction between such spins can then be exploited to demonstrate fundamental concepts such as entanglement, and a controlled-NOT operation between spins. Such an interaction is dependent on the orientation of the spin pair with respect to an applied external field. Using an asymmetric fullerene dimer with an individually addressable electron spin trapped in each fullerene unit, we shall have full control over a system of two coupled electron/nuclear spin pairs, capable of embodying up to four or more quantum bits (qubits). We intend to demonstrate quantum entanglement between the electron spins, and consequently a simple quantum computation such as the Deutsch-Josza algorithm. Finally, we shall attempt the same demonstration with the longer lived nuclear spins, in this case using the electron spins to distribute the entanglement. This ambitious experiment places strong demands on our ability to fabricate oriented arrays of functional nanocomposites, and thus forms a compelling demonstration of our new technology.