四波混频原子描述的极限
Limits on the atomic description of four-wave mixing
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中文总结 AI 辅助
该研究实验测试了单原子模型描述原子系综四波混频产生光子对的极限，发现需引入集体效应才能完全解释实验符合率。
中文摘要 AI 辅助
我们对在原子系综中金刚石构型下通过四波混频产生光子对的成熟单原子模型的极限进行了实验测试。使用冷原子源，双光子被产生并通过偏振分析仪检测，该分析仪在实验室坐标系中将发射光分解为水平和垂直分量。驱动第一和第二激发跃迁的泵浦激光分别具有水平和垂直偏振。为了预测所有偏振通道中的单光子计数和符合率，我们使用一个考虑相关超精细态所有塞曼子能级的综合模型直接计算了一阶和二阶关联函数。此外，我们比较了有无磁光阱再泵浦激光时的布居数动力学，揭示了塞曼子能级布居数的显著差异。这促使我们在最终模型中包含两个额外的超精细能级及其相应的塞曼子能级。所得的密度矩阵被用来计算远场电场算符的期望值，并在一定泵浦激光功率范围内与实验测量结果进行比较。在该范围的大部分区域内，与测量的光子计数获得了极好的一致性。对于符合测量，当第一（第二）衰变产生的光子偏振与第一（第二）泵浦光束平行时，发现一致性良好。相反，对于相反的偏振配置，模型始终低估了实验符合率。这些发现表明，需要超出单个原子内部能级动力学的效应，尤其是集体现象，才能完全解释原子系综中四波混频产生的光子符合。
英文摘要
The limits of the well-established single-atom model for describing photon-pair generation via four-wave mixing in a diamond configuration in atomic ensembles are experimentally tested. Using a cold-atom source, biphotons are generated and detected through polarization analyzers that resolve the emitted light into horizontal and vertical components in the laboratory frame. The pump lasers driving the first and second excitation transitions are horizontally and vertically polarized, respectively. To predict single-photon counts and coincidence rates in all polarization channels, the first- and second-order correlation functions are calculated directly using a comprehensive model that accounts for all Zeeman sublevels of the relevant hyperfine states. Furthermore, the population dynamics with and without the re-pump laser of the magneto-optical trap are compared, revealing substantial differences in the populations of the Zeeman sublevels. This motivates the inclusion of two additional hyperfine levels and their corresponding Zeeman sublevels in the final model. The resulting density matrix is used to calculate expectation values of the far-field electric-field operators and compare them with experimental measurements over a range of pump-laser powers. Excellent agreement with the measured photon counts is obtained over most of this range. For the coincidence measurements, good agreement is found when the polarization of the photon generated by the first (second) decay is parallel to that of the first (second) pump beam. In contrast, the model consistently underestimates the experimental coincidence rates for the opposite polarization configuration. These findings indicate that effects beyond the internal level dynamics of individual atoms, most notably collective phenomena, are required to fully account for photon coincidences generated by four-wave mixing in atomic ensembles.
发表机构
- Universidad Nacional Autónoma de México（墨西哥国立自治大学）
- Universidad Autónoma Metropolitana Azcapotzalco（阿兹卡波察尔科自治大学）
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