Verification of EPR paradox studied by measuring spin-correlations of two protons in pair

众所周知，爱因斯坦、波多尔斯基和罗森（EPR）断言，就局部实在论（经典物理学家的自然概念）而言，量子力学是不完整的。这有时被称为EPR悖论。贝尔证明了任何局部隐变量理论都会导致一个与量子力学预测相矛盾的不等式，从而使这一论点量化并易于实验验证。我们测量了自旋单重态[^1S_0]中两个质子（p-p）的自旋纠缠，利用贝尔不等式验证了一个隐变量理论。用自旋相关函数表示的结果可以与量子力学和贝尔不等式的预测相比较。在270mev下，用^1H(d, ^2He)n反应生成了高纯度的[^1S_0]态，并用新构造的偏振仪EPOL测量了它们的自旋相关性。该实验的新颖之处在于：a)使用几乎100%效率的“事件准备”探测器来制备无偏样品；b)一个完全接受2π sr的焦平面偏振计，其参考轴是随机的“后选择”。结果在99.3%的置信水平上违背了贝尔不等式。这是第一次在几乎无空穴的实验环境下，对大质量自旋1/2强子对强相互作用的局部隐变量理论（Bell）进行测试。我们还首次测量了不同粒子的自旋相关性，即由270 MeV的^2H(d, pn)pn反应产生的单重态质子-中子对。用epl测量了质子的自旋极化，用新型偏振仪NPOL测量了中子的自旋极化。数据分析正在进行中。1989年，Greenberger， Home和Zeiinger （GHZ）提出了一个有趣的关于三粒子纠缠的新定理。为了测试GHZ，需要对三个粒子进行自旋相关测量。我们成功地构建了一个用于正对电子衰变的三光子偏振计系统。总之，这个项目进行得很顺利，我们取得了很好的成绩。少

It is well-known that Einstein, Podolsky, and Rosen (EPR) asserted that quantum mechanics is incomplete in terms of local realism, a classical physicist's conception of nature. This is sometimes called as the EPR paradox. Bell rendered this argument quantitative and amenable to experimental verification as he showed that any local hidden variable theory will result in an inequality, which can contradict quantum mechanical predictions.We measured the spin entanglement of two protons (p-p) in the spin-singlet state [^1S_0] to test a hidden variable theory by using Bell's inequality. Results in terms of spin correlation function can be compared with predictions by the quantum mechanics as well as by the Bell's inequality. The high purity [^1S_0] state was produced by the ^1H(d, ^2He)n reaction at 270 MeV and their spin correlation was measured by the newly constructed polarimeter EPOL. Novel features of this experiment are a)use of "event-ready" detector of nearly 100% efficiency to prepa … More re an unbiased sample and b)a focal plane polarimeter of full 2π sr acceptance with a random "post-selection" of the reference axes. The result violates the Bell's inequality at a confidence level of 99.3%. This is the first-time test of the local hidden variable theories (Bell) involving strong interacting pair of massive spin 1/2 hadrons, in nearly loophole free experimental setting.We also measured for the first time the spin correlation of unlike particles, namely proton-neutron pairs in the singlet state which were produced by the ^2H(d, pn)pn reaction at 270 MeV. The proton spin-polarization was measured with EPOL and the neutron polarization was measured with newly constructed polarimeter NPOL. Data analysis is in progress.In 1989, Greenberger, Home and Zeiinger (GHZ) formulated an interesting new theorem for three-particle entanglement. To test GHZ a spin-correlation measurement for three particles is required. We have succeeded to constructed a polarimeter system for three photons for the decay of orthopositronium.In summary, this project went so smoothly and we obtained excellent results. Less