Appl Opt. 2023 Mar 20;62(9):2273-2277. doi: 10.1364/AO.484456.
Telecommunication wavelength-entangled photon sources (EPS) are indispensable systems for a fiber-based quantum network. We developed a Sagnac-type spontaneous parametric down conversion system adopting a Fresnel rhomb as a wideband and reasonable retarder. This novelty, to the best of our knowledge, enables the generation of a highly nondegenerate two-photon entanglement comprising the telecommunication wavelength (1550 nm) and quantum memory wavelength (606 nm for Pr:YSO) with only one nonlinear crystal. Quantum state tomography was performed to evaluate the degree of entanglement, and the fidelity with a Bell state |+⟩ with a maximum of 94.4% was obtained. Therefore, this paper shows the potential of nondegenerate EPSs that are compatible with both telecommunication wavelength and quantum-memory wavelength to be installed in quantum repeater architecture.
用于光纤量子网络的电信波长纠缠光子源（EPS）是不可或缺的系统。我们开发了一种 Sagnac 型自发参量下转换系统，采用菲涅耳菱形作为宽带和合理的延迟器。据我们所知，这种新颖性使得能够仅使用一个非线性晶体生成包含电信波长（1550nm）和量子存储波长（对于 Pr:YSO 为 606nm）的高度非简并双光子纠缠。通过量子态层析成像来评估纠缠程度，并获得与最大保真度为 94.4%的贝尔态 |+⟩的最大保真度。因此，本文展示了与电信波长和量子存储波长兼容的非简并 EPS 安装在量子中继器架构中的潜力。
