Controlling Rings of Trapped Ions for Quantum Information Applications

量子计算承诺通过利用量子物理的独特属性来加快计算速度，这些属性决定了量子系统可以同时处于多种状态。例如，在许多现代加密方案所依赖的大数的因式分解中，这种非经典的特性被称为“叠加”，可用于设计处理信息更快的新的计算机算法。困难在于，叠加态是如此脆弱，以至于即使是少量的噪音，例如来自电场的噪音，也可能会消除量子优势。该项目的目标是为量子计算建立一种新的囚禁离子的环状构型。到目前为止，使用囚禁离子作为逻辑比特的量子计算方案依赖于一串线性离子。这种新的环形结构将减少主导噪声源的影响，从而提高量子操作的精度。除了量子计算的好处外，环形还为研究量子力学背后的基础物理方面提供了机会，量子力学是目前最好地描述原子世界的理论。具体地说，由于离子环可以自由旋转，它允许研究大型旋转物体和对称系统中存在的效应。因此，该项目将探索量子信息处理的独特途径，提供对量子力学的新见解，并为学生在这一快速发展的技术领域提供新的可能性。对称离子环提供了机会来研究一些需要平移对称系统和环拓扑的现象，以及实现专门受益于环几何的量子门。然而，为了实现这些研究中的任何一项，对离子的量子态及其集体运动的高度控制是必要的。为此，环不仅要对称，而且要有良好的冷却，并有旋转自由度精确控制。为了达到这些目标，离子将被平面电极配置上方的振荡电场捕获。电极配置经过精心选择，以便将离子捕获在远离衬底对称性破坏缺陷的紧凑环中。为了确定环的对称度，需要冷却到低微开尔文范围内的温度。因此，将重点介绍各种冷却技术，包括在非对称构型中的基态冷却，然后绝热转变为对称环。对量子信息应用特别感兴趣的是旋转(量子)态变化的速率。在这一表征阶段之后，激光将被用来启动受控的旋转，这取决于存储在单个离子中的量子信息。这种相互作用将被用来实现任何有意义的量子计算的密钥操作，即以另一位的状态为条件的单个(QU)位的量子操作。

Quantum computing promises to speed up computations by exploiting the unique properties of quantum physics that dictates that quantum systems can be in multiple states at the same time. This non-classical property, called "superposition", can be used to design new computer algorithms that process information faster, as, for example, in the factorization of large numbers on which many modern encryption schemes rely. The difficulty is that superposition states are so fragile that even small amounts of noise, for example from electric fields, can remove the quantum advantage. The goal of this project is to establish a novel ring configuration of trapped ions for quantum computing. To date quantum computational schemes that employ trapped ions as the logical bits have relied on a linear string of ions. This new ring architecture will reduce the influence of the dominant noise source, thereby increasing the accuracy of the quantum operations. In addition to quantum computation benefits, the ring shape also opens up opportunities to study aspects of the fundamental physics behind quantum mechanics, the theory that currently best describes the atomic world. Specifically, because the ion ring can freely rotate, it allows for the study of effects present in large rotating objects and symmetric systems. Thus, the project will explore unique avenues towards quantum information processing and provide novel insights into quantum mechanics as well as offering students new possibilities in this rapidly-developing field of technology.A symmetric ring of ions offers the opportunity to study a number of phenomena requiring translationally symmetric systems and ring topologies as well as to implement quantum gates that benefit specifically from the ring geometry. However, in order to realize any of these studies, a high degree of control over the quantum state of the ions and their collective motion is necessary. For this, the ring must not only be symmetric but also well cooled and have the rotational degree of freedom precisely controlled. Towards these goals, ions will be trapped with oscillating electric fields above a planar electrode configuration. The electrode configuration is carefully chosen to trap the ions in a compact ring far away from symmetry breaking imperfections of the substrate. To establish the degree of symmetry of the ring, cooling to temperatures in the low microkelvin range will be required. Hence, emphasis will be given to various cooling techniques including ground state cooling in an asymmetric configuration followed by adiabatic transformation into a symmetric ring. Of particular interest for quantum information applications is the rate with which the rotational (quantum) state changes. After this characterization phase, laser light will be used to initiate controlled rotation depending on the quantum information stored in individual ions. This interaction will be used to implement the key operation for any meaningful quantum computing, namely quantum operations of an individual (qu)bit conditioned on the state of another bit.