We present experiments on polarization gradient cooling of Ca$^+$ multi-ion Coulomb crystals in a linear Paul trap. Polarization gradient cooling of the collective modes of motion whose eigenvectors have overlap with the symmetry axis of the trap is achieved by two counter-propagating laser beams with mutually orthogonal linear polarizations that are blue-detuned from the S$_{1/2}$ to P$_{1/2}$ transition. We demonstrate cooling of linear chains of up to 51 ions and 2D-crystals in zig-zag configuration with 22 ions. The cooling results are compared with numerical simulations and the predictions of a simple model of cooling in a moving polarization gradient.

中文翻译：

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一维和二维离子库仑晶体的极化梯度冷却

我们展示了线性保罗陷阱中 Ca$^+$ 多离子库仑晶体的极化梯度冷却实验。其特征向量与陷阱的对称轴重叠的集体运动模式的偏振梯度冷却是通过两个反向传播的激光束实现的，这些激光束具有相互正交的线性偏振，这些激光束从 S$_{1/2}$ 蓝色失谐到 P$_{1/2}$ 的过渡。我们展示了多达 51 个离子的线性链和具有 22 个离子的锯齿形配置的 2D 晶体的冷却。冷却结果与数值模拟和移动极化梯度中冷却的简单模型的预测进行了比较。