Experimental simulation of spin-1 states by second-order type-II parametric down-conversion

In this paper, by using the second-order parametric down-conversion of the nonlinear crystal, the spin-1 state is simulated by the two-photon polarization entangled modes. Through adjusting the laser pulse power density, the efficiency of second-order parametric down-conversion is enhanced. The intensity of the spin-1 state is 0.5/s. The fidelity of the state is up to F=0.891±0.002, and the contrast is C=17.3. The results provide a new method for Stern-Gerlach measurement on the spin-1 system.     

新形貌二氧化硅材料的制备及光学性质研究

采用物理热蒸发二氧化硅纳米颗粒和三氯化铁催化剂混合粉末的方法,制备了两种新形貌二氧化硅材料,并用扫描电子显微镜、X射线电子能谱和光致发光等手段分别研究了合成材料的结构、组分和光学特质。研究发现,合成的材料的形貌分别为"蘑菇状"和"花朵状",材料垂直于衬底生长,且发射中心波长为510nm稳定的蓝绿光。根据得到的实验结果,分析认为材料的生长机制符合催化剂决定的顶部生长模式,催化剂的不同形貌决定形成了两种不同形貌材料,并通过研究材料生长初期的照片,证明了上述推测的正确性。本研究为合成其它新形貌纳米材料提供了一种新方法。     

高保真偏振EPR纠缠态的制备

通过优化参量下转换产生EPR(Einstein-Podolsky-Rosen)纠缠态的方案,采用符合计数和后选择方法,制备了高保真度的EPR偏振纠缠态.结果表明,EPR纠缠态的保真度达到近0.99,EPR纠缠对的量度达到3 500Hz,克服了纠缠态的保真度和量度不能同时提高的局限,为多光子纠缠态的制备和双光子量子通信提...     

双模真空压缩态在相阻尼情况下的量子纠缠与非定域性

研究了双模真空压缩态在相阻尼情况下的非定域动力学和纠缠特性.在得出该系统密度演化算符的明晰表达式后,我们基于"宇旋算符"而引入合适的Bell算符,从而很好的揭示了该态的非定域性.通过计算其相对熵纠缠度,我们也很好的揭示出其纠缠特性.     

Experimental investigation of the influence of laser intensity on the quality of Einstein-Podolsky-Rosen entangled photons

Using spontaneous parametric down conversion, polarization post selection and coincidence counting technique, the polarization Einstein-Podolsky-Rosen (EPR) entangled states are prepared. Experimental studies on the efficiency, contrast and fidelity with different pump laser intensities are performed systematically. The results show that the pump laser intensity distinctly influences the quality of entangled photons, especially the contrast and the fidelity. On the other hand, the pump efficiency of entangled photons is almost invariable, namely the entangled source brightness increases linearly with the increase of pump laser power.     

非线性Jaynes-Cummings模型纠缠演化和最大纠缠态产生

利用数值计算的方法,研究了Kerr介质腔中的J-C模型二能级原子和单模光场作用过程中信息熵和纠缠演化,得到了Kerr效应对纠缠态纠缠性质的影响。结果表明,Kerr介质对耦合体系的纠缠度有强烈的影响,在合适的Kerr效应下,量子态将长时间保持最大纠缠。     

四比特超纠缠态的鲁棒性研究

利用参量下转换和复合分束器相干叠加的方法制备了四比特超纠缠Greenberger-HorneZeilinger(GHZ)态,测量了纠缠体系的对比度和保真度。通过理论分析Ardehali不等式,得到了四比特纠缠体系的实验可测Ardehali算符。进而利用Ardehali算符在比特反转噪声环境中的期望值和噪声强度的关系,实验研究了四比特超纠缠体系的鲁棒性。结果表明,Ardehali不等式相对于定域实在论结果的违背随噪声强度的增加而下降。     

用超对称幺正变换解具有逆场算符的Jaynes—Cummings模型

对于具有逆场算符的Jaynes-Cummings Hamiltonian，我们发现了它的超对称结构，并应用超对称幺正变换的方法将其对角化，从而得到了它的本征值、本征态，同时也计算了态的演化和跃迁几率。     

Experimental investigation of the CHSH-class inequality and its robustness in noisy environments

Shimony-Holt (CHSH) inequality and investigate the robustness of the CHSH-class inequality in the bit-flip noisy environment. We obtain the experimental results of CHSH inequalityand analog CHSH inequalityas SCHSH=2.64±0.02 and SanalogCHSH=2.76±0.02, respectively, and prove that the analog CHSH inequality is more robust against bit-flip noise than the CHSH inequality. It provides better advantages for the experimental study and application. This work has been supported by the National Natural Science Foundation of China (Nos.11174224, 11404246 and 11447225), and the Natural Science Foundation of Shandong Province (Nos.ZR2013FM001, BS2015DX015 and ZR2014JL029). E-mail:zhaojiaqiang@wfu.edu.cn