三光子广义GHZ态中三体纠缠和非定域性研究

Tripartite entanglement and nonlocality in three-photon generalized GHZ states

一组具有普适性的新型Bell不等式能够清晰地描述三比特广义GHZ态(Generatized GreenbergerHorne-Zeilinger,GGHZ)非定域性和三体纠缠的关系.利用高能量的飞秒激光参量转换制备了三光子GGHZ纠缠态,采用量子态层析方法计算得到态的保真度为84%.基于制备的高保真度三光子GGHZ态测量了新型Bell算符和Bell不等式,得到了和理论一致的结果,并实验验证了Das提出的理论.实验结果表明新Bell不等式对定域实在论的违背随GGHZ态纠缠度增加而单调增加,GGHZ态的非定域性与三体纠缠程度直接相关.

A set of new Bell inequalities with universality can clearly describe the relationship between the nonlocality and three-body entanglement of three-qbit generalized Greenberger-Horne-Zeilinger（GGHZ）states. Three-photon GGHZ entangled states are prepared by using high-energy femtosecond laser parametric conversion. The state fidelity calculated by quantum state chromatography is 84%. A novel Bell operator and Bell inequality are measured based on the high fidelity three-photon GGHZ state. The results are in agreement with the theory, and the theoretical results proposed by Das are verified by experiments. Experimental results show that the violation to the local realism of the new Bell inequality increases monotonously with the increasing of GGHZ states entanglement degree. The nonlocality of GGHZ states is directly related to the degree of three-body entanglement.