Enabling technologies for rare-earth ion quantum memories

电介质晶体中稀土离子的特性使其在现代光学技术中不可或缺。最近，它们也被发现是量子信息处理和量子通信中许多应用的非常有趣的候选者：核自旋亚能级的长寿命允许量子信息存储几秒钟，而光学跃迁允许快速灵活的操作，并直接连接到“飞行量子比特”和远程单元。实现这一潜力需要选择合适的材料和发展适当的控制技术。在这个项目中，我们将对几种可能的候选材料进行表征，并确定它们的光学和自旋哈密顿参数。利用这些结果，我们将开发实验和理论技术来存储材料中的光量子态，将它们转移到核自旋自由度，并将存储的量子比特保存更长时间。我们将使用激光和射频磁场的组合来实现所需的控制操作。这些操作将针对精度和鲁棒性进行优化，即它们将对控制参数（如激光频率和射频场振幅）的不必要变化不敏感。为此，我们将借鉴相关领域取得的成果，特别是液态核磁共振。该项目的成果有望在量子信息处理和通信领域，以及时间分辨磁共振和高分辨激光光谱学领域产生回报。

The properties of rare-earth ions in dielectric crystals have made them indispensable in modern optical technologies. Recently, they have also been discovered as very interesting candidates for a number of applications in quantum information processing and quantum communication: the long lifetimes of nuclear spin sublevels allow storage of quantum information for several seconds, while the optical transitions allow fast and flexible manipulation and direct interfacing to ’flying qubits’ and remote units. Realization of this potential requires the selection of a suitable material and the development of the appropriate control techniques. In this project, we will characterize several possible candidate materials and determine their optical and spin Hamiltonian parameters. Using these results, we will develop experimental and theoretical techniques for storing optical quantum states in the material, transferring them to nuclear spin degrees of freedom, and preserving the stored qubits for extended time periods. We will use a combination of laser and radio-frequency magnetic fields for implementing the required control operations. These operations will be optimized for precision and robustness, i.e. they will be insensitive to unwanted variations of control parameters like laser frequency and radio-frequency field amplitude. For this purpose, we will draw on the results achieved in related fields, especially liquid-state nuclear magnetic resonance. The results of this project are expected to have payoffs for the field of quantum information processing and communication, but also for time-resolved magnetic resonance and high resolution laser spectroscopy.