非对称偏振三维纠缠态的预警制备

在量子信息处理过程中,量子纠缠态扮演着极为重要的角色,其特殊的物理性质,使得量子信息具有经典信息所没有的许多新的特征,为信息传输和信息处理提供了新的物理资源.针对非对称偏振三维纠缠态的制备,基于交叉相位调制技术,以纠缠光子对和两个单光子比特作为初态,通过单光子与相干光的相互作用以及双光子干涉来实现.如果通过三个非计数单光子探测器来预警制备三维最大纠缠态,其概率为3/64.而如果采用特殊的分段式光子探测器,其概率可以提高到3/8,达到理论极限值.该方案在理论上是可行的,效率相对较高,而且预警式的制备为其后续在量子信息过程中的使用提供了很大的灵活性.

Heralded generation of asymmetric polarized entangled qutrits

In quantum information processing, quantum entanglement plays a very important role with special physical property, which makes the quantum information have many new characteristics that the classical information do not have, and provides a new physical resource in the transmission and processing of information. Compared with classical bit, quantum entanglement, especially the high dimensional quantum entanglement （i.e., entangled qudit）, has a large information storage space and good security confidentiality, which means stronger nonlocality and much more powerful capability in quantum information processing. In this sense, here we focus on the topic of polarized entangled qudit generation, especially the asymmetric entangled qutrit generation, which hasn＇t been discussed before. The initial states could be an entangled photon pair and two single photons. Using two qubus beams as ancilla, and based on the cross phase modulation, the initial quantum states could be projected into different subspaces, which include the desired one. Finally, through the bi-photon Hong-Ou-Mandel interference, the asymmetric entangled qutrit could be generated. This scheme is heralded by the detection results of three ideal photon number non-resolving detectors （PNNDs）. If neither of the three ideal PNNDs registers photons, the generation is successful; otherwise, any click appearing on one of the three ideal PNNDs means the failure of the generation. The corresponding success probability of maximally entangled qutrit generation is 3/64, which is relatively small. However, the success probability could be increased to 3/8 by using the special photon detectors, associated with the quantum non- demolition detectors （QNDs） replacing the ideal PNNDs. The more efficient scheme is still heralded, so the generated entangled qutrit could be used flexibly in the quantum information processing.