Accurate measurement of relative distance and orientation of two nearby quantum particles is discussed. We are in particular interested in a realistic description requiring as little prior knowledge about the system as possible. Thus, unlike in previous studies, we consider the case of an arbitrary relative orientation of the two atoms. For this, we model the atom with complete Zeeman manifolds, and include parallel as well as orthogonal dipole-dipole couplings between all states of the two atoms. We find that it is possible to determine the distance of the two atoms independent of the orientation, as long as the particles are sufficiently close to each other. Next, we discuss how in addition the alignment of the atoms can be measured. For this, we focus on the two cases of atoms in a two-dimensional waveguide and of atoms on a surface.
Modified One-Axis-Twist Squeezing for Deterministic Orientation Control of Schrödinger Cat States with Unknown Atom-Number Parity
Department of Physics and Astronomy, Northwestern University（西北大学物理与天文学系）；Department of Electrical and Computer Engineering, Northwestern University（西北大学电气与计算机工程系）
Towards the explicit computation of Bohm velocities associated to N-electron wave-functions with arbitrary spin-orientations
多粒子薛定谔方程的直接解对于非常少的电子是无法计算的。为了超越这一限制，作者之一[X. Oriols，Phys. Rev. Lett. 2007，98（066803）]最近提出了一个新的模型来研究电子-电子关联从玻姆轨迹与时间相关的波包解的伪单粒子薛定谔方程。在上述论文中，假设所有电子具有相同的自旋取向，仅考虑轨道交换相互作用。然后，多粒子波函数是单粒子波包的复斯莱特行列式。本文将以前的形式扩展到研究电子具有不同自旋取向的多粒子波函数，用含时波包处理N个不同电子自旋取向的主要困难是必须研究所有可能的N！N！N！自旋状态之间的排列的产物。为了克服这一计算上难以实现的问题，本文将总波函数视为两个多粒子波函数的分离产物，第一个是自旋向上的，第二个是自旋向下的。为了数值证明这种近似，玻姆速度在不同的反对称的总波函数的情况下计算。计算结果证实了我们的近似在大量情况下的准确有效性。
Enhanced atom-by-atom assembly of arbitrary tweezers arrays
我们报告了扩展[Barredo et al.，Science 354，1021（2016）]，我们使用它在光镊中创建超过100个单原子的满载目标阵列，从随机加载的半填充初始阵列开始。我们描述了四种变体的排序算法，（i）允许减少组装所需的移动次数，以及（ii）允许组装任意的非规则目标阵列。最后，我们实验证明了这种增强的汇编程序的各种目标阵列的性能。
