Quantum information processing with hybrid systems

我们提议研究由超冷原子和离子组成的混合量子系统。冷中性原子和被困离子的相互作用提供了大量有趣的新物理问题。它们涵盖了从超冷量子化学到量子信息处理的新概念，再到真正的量子多体物理。我们计划用超冷原子和离子来探索量子化学的各个方面，以获得对这种混合系统中相互作用的充分理解。我们将研究低能碰撞的机制，并寻找费什巴赫共振来调节原子和离子之间的相互作用强度。此外，我们将研究玻色-爱因斯坦凝聚体和单个离子之间化学反应的集体效应。利用原子-离子混合物的特殊特性，我们将使用混合系统进行量子信息处理。特别是，我们计划用玻色-爱因斯坦凝聚体实现离子的交感基态冷却，为量子信息处理实验做准备。当离子浸入到超冷的中性原子环境中时，退相干的性质将通过调整环境的性质来调整：当离子与一维玻色气体耦合时，预测到耗散量子相变。此外，我们计划在光学晶格中实现由单个离子和中性原子阵列组成的可扩展混合量子处理器。第三个方向是研究量子多体物理中的杂质效应。我们计划研究通过单一杂质或原子量子点的输运，目标是实现单原子晶体管。单原子晶体管将杂质的量子态相干地转移到宏观中性原子电流，从而可以实现单个原子量子位的量子不拆除测量。

We propose to investigate hybrid quantum systems composed of ultracold atoms and ions. The mutual interaction of the cold neutral atoms and the trapped ion offers a wealth of interesting new physical problems. They span from ultracold quantum chemistry over new concepts for quantum information processing to genuine quantum many-body physics. We plan to explore aspects of quantum chemistry with ultracold atoms and ions to obtain a full understanding of the interactions in this hybrid system. We will investigate the regime of low energy collisions and search for Feshbach resonances to tune the interaction strength between atoms and ions. Moreover, we will study collective effects in chemical reactions between a Bose-Einstein condensate and a single ion. Taking advantage of the extraordinary properties of the atom-ion mixture we will perform quantum information processing with hybrid systems. In particular, we plan to realize sympathetic ground state cooling of the ion with a Bose-Einstein condensate to prepare it for experiments in quantum information processing. When the ion is immersed into the ultracold neutral atom environment the nature of the decoherence will be tailored by tuning properties of the environment: A dissipative quantum phase transition is predicted when the ion is coupled to a one-dimensional Bose gas. Moreover, we plan to realize a scalable hybrid quantum processor composed of a single ion and an array of neutral atoms in an optical lattice. The third direction we will pursue is the study of impurity effects in quantum many-body physics. We plan to study transport through a single impurity or atomic quantum dot with the goal of realizing a single atom transistor. A single atom transistor transfers the quantum state of the impurity coherently to a macroscopic neutral atom current and can thus realize quantum non-demolition measurements of individual atomic qubits.