Non-signalling boxes (NS) are theoretical resources defined by the principle of no-faster-than-light communication. They generalize quantum correlations, and some of them are known to collapse communication complexity (CC). However, this collapse is strongly believed to be unachievable in Nature, so its study provides intuition on which theories are unrealistic. In the present letter, we find a better sufficient condition for a nonlocal box to collapse CC, thus extending the known collapsing region. In some slices of NS, we show this condition coincides with an area outside of an ellipse.
Understanding the structure of nonlocal correlations is important in many fields ranging from fundamental questions of physics to device-independent cryptography. We present a protocol that can convert extremal two-party--two-input nonlocal no-signaling boxes of any type into any other extremal two-party--two-input nonlocal no-signaling box perfectly. Our results are exact, and even though the number of required boxes cannot be determined in advance, their expected number is finite. Our protocol is adaptive and demonstrates for the first time the usefulness of using no-signaling boxes in diffe…
Exploring Bell Nonlocality with Extremal Non-Signaling Boxes
Instituto Superior Técnico(里斯本高等技术学院);Instituto de Telecomunicações(电信研究所);Q*Bird BV(Q*Bird有限公司);INL – International Iberian Nanotechnology Laboratory(伊比利亚纳米技术国际实验室);Sorbonne Université, CNRS, LIP6(索邦大学,法国国家科学研究中心,LIP6实验室);Zuse Institute Berlin(柏林祖斯研究所);Universidad de Sevilla(塞维利亚大学);Instituto Carlos I de Física Teórica y Computacional, Universidad de Sevilla(塞维利亚大学卡洛斯一世理论与计算物理研究所);Inria, ENS de Lyon, UCBL, LIP(法国国家信息与自动化研究所,里昂高等师范学院,里昂第一大学,LIP实验室)
Three-input Majority Function as the Unique Optimal Function for the Bias Amplification using Nonlocal Boxes
[Phys. Rev. Lett. 96,250401(2006)]表明,CHSH概率大于$\frac{3+\sqrt{6}}6$的共享非局部盒产生微不足道的通信复杂度。与量子力学可达到的最大CHSH概率$\frac{2+\sqrt{2}}4$之间仍然存在差距。这是一个有趣的开放式问题,以确定确切的阈值为微不足道的通信复杂性。Escherard等人的思想是基于3输入多数函数的递归偏置放大。其他函数的选择是否表现出更强的偏置放大作用并不明显。我们表明,3-输入多数函数是唯一的最优,所以不能提高阈值$\frac{3+\sqrt{6}}6$的Escherard等人。的偏置放大。在这项工作中,用于计算用于偏置放大的函数的协议被限制为非自适应协议或特定的自适应协议的启发Pawnesowski等人。的信息因果关系方案[Nature 461,1101(2009)]。首先,我们展示了一个新的自适应协议的灵感Pawkenowski等人。的协议,并表明新的自适应协议是优于任何非自适应协议。最后,我们表明,3-输入多数函数是唯一的最佳偏置放大,如果我们应用新的自适应协议的每一步的偏置放大。
We carry out a thought experiment in an imaginary world. Our world is both local and realistic, yet it violates a Bell inequality more than does quantum theory. This serves to debunk the myth that equates local realism with local hidden variables in the simplest possible manner. Along the way, we reinterpret the celebrated 1935 argument of Einstein, Podolsky and Rosen, and come to the conclusion that they were right in their questioning the completeness of the Copenhagen version of quantum theory, provided one believes in a local-realistic universe. Throughout our journey, we strive to explain…