We investigate the performance of a certain nonclassicality identifier, expressed via integrated second-order intensity moments of optical fields, in revealing bipartite entanglement of quantum-optical frequency combs (QOFCs), which are generated in both spontaneous and stimulated parametric down-conversion processes. We show that, by utilizing that nonclassicality identifier, one can well identify the entanglement of the QOFC directly from the experimentally measured intensity moments without invoking any state reconstruction techniques or homodyne detection. Moreover, we demonstrate that the stimulated generation of the QOFC improves the entanglement detection of these fields with the nonclassicality identifier. Additionally, we show that the nonclassicality identifier can be expressed in a factorized form of detectors quantum efficiencies and the number of modes, if the QOFC consists of many copies of the same two-mode twin beam. As an example, we apply the nonclassicality identifier to two specific types of QOFC, where: (i) the QOFC consists of many independent two-mode twin beams with non-overlapped spatial frequency modes, and (ii) the QOFC contains entangled spatial frequency modes which are completely overlapped, i.e., each mode is entangled with all the remaining modes in the system. We show that, in both cases, the nonclassicality identifier can reveal bipartite entanglement of the QOFC including noise, and that it becomes even more sensitive for the stimulated processes.
Versatile control of $^9$Be$^+$ ions using a spectrally tailored UV frequency comb
我们演示了光学频率梳直接实现的$^9$ Be $^+$离子的量子控制。基于对不同磁场条件下$^9$ Be $^+$中相关过程的数值模拟，我们证明了控制梳状结构光谱特性的广泛适用性。我们介绍了一种新的技术，用于选择性和有效地产生光谱定制的窄带宽光学频率梳近313 nm。我们实验证明内部状态控制和内部运动态耦合的$^9$的$^+$离子实施的受激拉曼操作使用光谱优化的光学频率梳。我们的脉冲激光方法是在潘宁陷阱中实现量子逻辑和量子信息实验的关键一步。
