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摘要: 量子纠缠是量子信息领域的核心资源，目前利用β型硼酸钡（BBO）晶体参量下转换制备的纠缠光子对的亮度较低，它直接制约了量子通信的最远距离，已无法满足星地实用化量子通信的发展需求.利用周期极化KTiOPO4晶体，采用准相位匹配技术设计产生了一种后选择的纠缠源，测得的符合计数达到了16×103s-1 mW-1，极化对比度达到27∶1，在亮度上比基于BBO的量子纠缠光源提高了一个数量级以上.这一高亮度的纠缠源可以广泛应用于量子密钥分发、量子隐形传态以及量子计算等新兴量子信息领域，为实现全球化量子通信提供了有力的保障.
Abstract: Entangled states are key resource for quantum information processing. In linear optics quantum computing，the most widely used entanglement resource is polarization entangled photon pairs generated via type-Ⅱ spontaneous parametric down-conversion. However，the brightness is not sufficient to perform quantum communication experiment between ground and satellite. In this paper we have developed a high-brightness entangled resource based on periodic polarization and quasi-phase marched periodically poled KTiOPO4 crystal. The number of generated entangled pairs is about 1.6×104s-1mW-1 and the visibility is 27∶1. Our source is with about one order of magnitude brighter than previous sources based on β-barium borate crystal. This leads to an immediate possibility for applications in the field of quantum key distribution，quantum teleportation and quantum computation. Particularly it would form a solid basis for future global quantum network.
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