Photonic quantum states generated from atomic ensembles will play important roles in future quantum networks and long-distance quantum communication because their advantages, such as universal identity and narrow spectral bandwidth, are essential for quantum nodes and quantum repeaters based on atomic ensembles. In this study, we report the collectively coherent superposition of biphoton wavefunction emitted from different velocity classes in a Doppler-broadened cascade-type atomic ensemble. We experimentally demonstrate that the three times difference of temporal width of both biphoton temporal waveforms varies dependent on the wavelengths of the signal and idler photons from both 6S_1/2–6P_3/2–6D_5/2 and –8S_1/2 transitions of ¹³³Cs, corresponding to the idler and signal wavelengths of 852 nm–917 nm and 852 nm–795 nm, respectively. Our results help understand the characteristics of biphoton sources from a warm atomic ensemble and can be applied to long-distance quantum networks and practical quantum repeaters based on atom–photon interactions.

中文翻译：

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多普勒展宽原子系综产生的光子对的集体双光子时间波形


由原子系综产生的光子量子态将在未来的量子网络和长距离量子通信中发挥重要作用，因为它们的通用身份和窄光谱带宽等优点对于基于原子系综的量子节点和量子中继器至关重要。在这项研究中，我们报告了多普勒展宽级联型原子系综中不同速度等级发射的​​双光子波函数的集体相干叠加。我们通过实验证明，两个双光子时间波形的时间宽度的三倍差异取决于来自 6S _1/2 –6P _3/2 –6D _5/2和 –8S _1/2跃迁的信号和闲频光子的波长。 ¹³³ Cs，分别对应闲频波长和信号波长 852 nm-917 nm 和 852 nm-795 nm。我们的结果有助于理解来自热原子系综的双光子源的特性，并且可以应用于基于原子-光子相互作用的长距离量子网络和实用量子中继器。