Quantum computing and quantum communication, have been greatly developed in recent years and expected to contribute to quantum internet technologies, including cloud quantum computing and unconditionally secure communication. However, long-distance quantum communication is challenging mainly because of optical fiber losses; quantum repeaters are indispensable for fiber-based transmission because unknown quantum states cannot be amplified with certainty. In this study, we demonstrate a versatile entanglement source in the telecom band for fiber-based quantum internet, which has a narrow linewidth of sub-MHz range, entanglement fidelity of more than 95%, and Bell-state generation even with frequency multimode. Furthermore, after a total distribution length of 20-km in fiber, two-photon correlation is observed with an easily identifiable normalized correlation coefficient, despite the limited bandwidth of the wavelength converter. The presented implementation promises an efficient method for entanglement distribution that is compatible with quantum memory and frequency-multiplexed long-distance quantum communication applications.

近年来，量子计算和量子通信得到了极大的发展，并有望为量子互联网技术做出贡献，包括云量子计算和无条件安全通信。但是，长距离量子通信的挑战主要是由于光纤损耗。量子中继器对于基于光纤的传输是必不可少的，因为无法确定地放大未知的量子态。在这项研究中，我们展示了基于光纤的量子互联网在电信频段中的通用纠缠源，它具有小于MHz范围的窄线宽，超过95％的纠缠保真度，甚至在使用多模频率时也能产生钟形。此外，在光纤总分布长度为20公里之后，尽管波长转换器的带宽有限，但观察到的两个光子相关具有易于识别的归一化相关系数。提出的实现方式有望实现一种有效的纠缠分布方法，该方法与量子存储器和频率复用的长距离量子通信应用兼容。