Rydberg excited Calcium Ions for Quantum Interactions

捕获冷离子是实现量子信息处理的最先进的系统之一。在目前的实验中，量子比特的纠缠是通过对离子晶体（集体）运动的量子控制来实现的，以长寿命的内部原子状态为代表。相反，我们提出了一个由理论支持的前所未有的实验计划，其中与里德堡激发离子相关的巨大偶极矩是极强的自旋依赖的远程相互作用的基础，因此，作为量子计算和量子模拟的基本构建块，异常快速的纠缠操作。虽然在短期内需要探索的基本问题是理解里德堡激发和存储在线性保罗阱中的单个和多个离子的动力学，以及用外部电磁场操纵这种动力学的各种方法，但这个项目的长期承诺是一个潜在的可扩展的非常快速的离子阱量子处理器，特别是一个新的有效的自旋模型量子模拟器。对于具有拓扑相的奇异物质的海森堡型相互作用。一个主要的实验挑战是离子里德堡激发对122nm附近相干光源的要求。我们的联盟处于一个非凡而独特的情况下，在一个实验室里，这些相干光源和先进的离子量子计算装置都是可用的，从而使我们能够在相对较短的时间尺度上探索这个极有前途的里德堡离子量子信息处理的新前沿。计划中的实验将基于已建立的离子捕获、量子态探测和激光场操纵技术。提出了一种改进的量子搁置方法，即使在大晶体中对单个离子也能以统一的检测效率检测里德伯态跃迁。首先我们将精确地确定离子里德伯态的能级和原子性质，然后我们将目标对准相邻离子的相互里德伯态相互作用。这种门相互作用，里德堡诱导的量子相变和由此产生的量子态的完整层析成像受益于量子信息处理中高度发达的方案。在未来，超越三年项目的实验范围，快速里德堡离子量子逻辑运算可能与传统的门方案和现代离子阱技术相结合。

Trapped cold ions are among the most advanced systems to implement quantum information processing. In current experiments entanglement of the qubits, represented by long lived internal atomic states, is achieved via quantum control of the (collective) motion of the ion crystal. Instead, we propose an unprecedented experimental program supported by theory, where the huge dipole moments associated with Rydberg excited ions are the basis of extremely strong spin-dependent long range interactions, and thus exceptionally fast entangling operations as basic building blocks for quantum computing and quantum simulation. While in the short term the fundamental questions to be explored are the understanding of Rydberg excitation and dynamics of single and multiple ions stored in linear Paul traps, and the various ways of manipulating this dynamics with external electromagnetic fields, the long term promise of this project is a potentially scalable very fast ion trap quantum processor, and in particular also a novel efficient quantum simulator of spin models, for Heisenberg type interactions to exotic matter with topological phases. A main experimental challenge is the requirement of a coherent light source near 122nm for the ion Rydberg excitation. Our consortium is in the remarkable and unique situation where in a single laboratory both these coherent light sources as well as advanced ion quantum computing setups are available, thus allowing us to explore this extremely promising new frontier of Rydberg ion quantum information processing on a comparatively short time scale. The planned experiments will be based on the well established techniques of ion trapping, quantum state detection and manipulation with laser fields. An adapted quantum shelving method is proposed to detect transitions to Rydberg states with unity detection efficiency on individual ions even in large crystals. Initially we will accurately determine energy levels and atomic properties of ion Rydberg states, and then we aim for mutual Rydberg state interactions of adjacent ions. Such gate interactions, Rydberg induced quantum phase transitions and a full tomography of the resulting quantum state benefit from the highly developed schemes in quantum information processing. In the future, beyond the experimental horizon of the three-year project, fast Rydberg ion quantum logic operations could possibly be combined with the conventional gate schemes and modern ion trap technology.