Recent progress in quantum technologies with ultracold atoms has been propelled by spatially fine-tuned control of lasers and diffraction-limited imaging. The state-of-the-art precision of optical alignment to achieve this fine-tuning is reaching the limits of manual control. Here, we show how to automate this process. One of the elementary techniques of manual alignment of optics is cross-walking of laser beams. Here, we generalize this technique to multi-variable cross-walking. Mathematically, this is a variant of the well-known Alternating Minimization (AM) algorithm in convex optimization and is closely related to the Gauss-Seidel algorithm. Therefore, we refer to our multi-variable cross-walking algorithm as the modified AM algorithm. While cross-walking more than two variables manually is challenging, one can do this easily for machine-controlled variables. We apply this algorithm to mechanically align high numerical aperture (NA) objectives and show that we can produce high-quality diffraction-limited tweezers and point spread functions (PSF). After a rudimentary coarse alignment, the algorithm takes about 1 hour to align the optics to produce high-quality tweezers. Moreover, we use the same algorithm to optimize the shape of a deformable mirror along with the mechanical variables and show that it can be used to correct for optical aberrations produced, for example, by glass thickness when producing tweezers and imaging point sources. The shape of the deformable mirror is parametrized using the first 14 non-trivial Zernike polynomials, and the corresponding coefficients are optimized together with the mechanical alignment variables. We show PSF with a Strehl ratio close to 1 and tweezers with a Strehl ratio >0.8. The algorithm demonstrates exceptional robustness, effectively operating in the presence of significant mechanical fluctuations induced by a noisy environment.
我们演示了单个碱土原子在光镊中的单次成像和窄线冷却，特别是被困在$515.2~\text{nm}$光中的锶-88原子。我们实现高保真单原子分辨成像检测光子从宽单重态跃迁，而冷却的窄相互组合线，并将这种技术扩展到高度均匀的二维阵列的$121$镊子。成像过程中的冷却是基于以前未观察到的窄线西西弗斯机制，我们预测这将适用于各种各样的实验情况。此外，我们证明了光分辨边带冷却的单原子接近运动的基态的镊子。在成像过程中损失的精确测定表明，从$^1$ P $_1$到$^1$ D $_2$的分支比比通常引用的大两倍以上，这也是我们的从头计算预测的差异。我们还测量了在$515.2~\text{nm}$镊子中的互组合线的微分极化率，并通过将镊子极化从线性调谐到椭圆来实现魔捕配置。我们目前的计算，与我们的结果一致，预测魔术交叉线偏振在$520(2)~\text{nm}$和交叉独立的偏振在500.65（50）nm。我们的研究结果为基于镊子中单独控制的碱土原子的广泛的新实验途径铺平了道路-从原子物理学的基础实验到量子计算，模拟和计量实施。
Preparation of hundreds of microscopic atomic ensembles in optical tweezer arrays
我们提出了可编程的二维阵列的微观原子系综组成的400多个网站，几乎均匀的填充和小的原子数波动。我们的方法涉及直接投影的光图案从数字图像处理设备具有高的空间分辨率到一个光学煎饼陷阱作为一个水库。这使得可以在单个步骤中以高占用数量和每个镊子的低功率要求装载大的镊子阵列。每个原子系综被限制为$\sim 1\,μ$ m $^3$，具有从20到200个原子的可控占据和（亚）泊松原子数波动。因此，它们非常适合于量子模拟和实现集体编码的里德堡原子量子比特的大阵列，用于量子信息处理。
School of Physics and Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China（中国人民大学物理学院及量子态构建与操控教育部重点实验室）
