Excitation with entangled photon pairs may lead to an increase in the efficiency of two-photon absorption at low photon flux. The corresponding process, entangled two-photon absorption (E2PA), has been investigated in numerous theoretical and experimental studies. However, significant ambiguity and inconsistency remain in the literature about the absolute values of E2PA cross sections. Here, we use a fluorescence-based registration scheme to experimentally determine upper bounds on the cross sections for six fluorophores. These bounds are up to 4 orders of magnitude lower than the smallest published cross section. For two samples that have been studied by others, Rhodamine 6G and 9R-S, we measure upper bounds 4 and 5 orders of magnitude lower than the previously reported cross sections.

中文翻译：

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在常见的荧光团中纠缠的两个光子吸收截面上设置边界

纠缠光子对的激发可能导致低光子通量下双光子吸收效率的提高。纠缠双光子吸收（E2PA）的相应过程已在许多理论和实验研究中进行了研究。但是，关于E2PA横截面的绝对值，文献中仍然存在明显的歧义和不一致之处。在这里，我们使用基于荧光的配准方案来实验确定六个荧光团的横截面上限。这些边界比最小的已发布横截面低4个数量级。对于其他人研究过的两个样品，若丹明6G和9R-S，我们测量的上限比以前报告的横截面低4和5个数量级。