EPR-Bell Tests with Unsharp Observables and Relativistic Quantum Measurement
P. Busch
备注:
20 pages LaTeX. Contribution to NATO Advanced Research Workshop "Modality, Probability, and Bell's Theorem", Cracow, Poland, 19.-23.8.01
发表信息:
In: Non-locality and Modality, eds. T. Placek, J. Butterfield, Springer-Verlag, NATO Science Series II. Mathematics, Physics and Chemistry - Vol. 64 (2002), pp. 175-193. ISBN: 978-1-4020-0662-3
In this contribution I will review the analysis of the Einstein-Podolsky-Rosen argument, Bell's inequalities and of associated experiments for spins in terms of positive operator valued measures. Specifically, I will explore the relation between the Clauser-Horne-Shimony-Holt inequality and a fundamental \emph{classicality} property of observables -- their \emph{coexistence}. A derivation of Bell's inequalities for unsharp spins will be given which follows a reconstruction by Mittelstaedt and Stachow of the original EPR argument. In this context we discuss the need for a consistent relativistic description of localised measurements, carried out in spacelike separated regions of spacetime on spatially extended, entangled systems.
Bell nonlocality and Einstein-Podolsky-Rosen (EPR) steering are every important quantum correlations of a composite quantum system. Bell nonlocality of a bipartite state is a quantum correlation demonstrated by some local quantum measurements, while EPR steering is another form of quantum correlations, observed firstly by Schrodinger in the context of famous EPR paradox. In this paper, we give some remarks on Bell nonlocality and EPR steering of bipartite states, including mathematical definitions and characterizations of these two quantum correlations, the convexity and closedness of the set …
Federal University of Paraná(联邦巴拉那大学);University of Geneva(日内瓦大学);Lund University(隆德大学);Constructor University(Constructor 大学);Uppsala University(乌普萨拉大学);KTH Royal Institute of Technology and Stockholm University(皇家理工学院和斯德哥尔摩大学)
As a way of saving quantum resources, recycling of Bell nonlocality has been experimentally studied, but restricted to sequential unsharp measurements. However, it has been theoretically shown recently that projective measurements are sufficient for recycling nonlocality [Phys. Rev. Lett. \textbf{129}, 230402 (2022)]. Here, we go beyond unsharp measurement scenarios and experimentally demonstrate the recycling of nonlocal resources with projective measurements. By verifying the violation of Clauser-Horne-Shimony-Holt (CHSH) inequality, we find that three independent parties can recycle the Bel…
We study the Bell inequality in a holographic model of the casually disconnected Einstein-Podolsky-Rosen (EPR) pair. The Clauser-Horne-Shimony-Holt(CHSH) form of Bell inequality is constructed using holographic Schwinger-Keldysh (SK) correlators. We show that the manifestation of quantum correlation in Bell inequality can be holographically reproduced from the classical fluctuations of dual accelerating string in the bulk gravity. The violation of this holographic Bell inequality supports the essential quantum property of this holographic model of an EPR pair.
An explicit model-example is presented to simulate Einstein-Podolsky-Rosen (EPR) experiments without invoking instantaneous influences at a distance. The model-example, together with the interpretation of past experiments by Kwiat and coworkers, uncovers logical inconsistencies in the application of Bell's theorem to actual EPR experiments. The inconsistencies originate from topological-combinatorial assumptions that are both necessary and sufficient to derive all Bell-type inequalities including those of Wigner-d'Espagnat and Clauser-Horne-Shimony-Holt. The model-example circumvents these inc…
In a previous paper tests for entanglement for two mode systems involving identical massive bosons were obtained. In the present paper we consider sufficiency tests for EPR steering in such systems. We find that spin squeezing in any spin component, a Bloch vector test, the Hillery-Zubairy planar spin variance test and squeezing in two mode quadratures all show that the quantum state is EPR steerable. We also find a generalisation of the Hillery-Zubairy planar spin variance test for EPR steering. The relation to previous correlation tests is discussed. This paper is based on a detailed classif…
局域实在论已经被基于贝尔定理的纠缠粒子实验所推翻。Bell,Physics(Long Island City,N.Y.)1,195(1964))。然而,关于问题是局部性还是现实性的争论一直在继续。在这项工作中,我们分析了爱因斯坦-波多尔斯基-罗森思想实验玻姆的版本,用信息论和热力学。从EPR实验中推断非定域性将违背量子力学的非实在性原理。因此,有关量子纠缠的实验不能提供任何证据来指责局域性。
Entanglement, EPR steering, and Bell-nonlocality criteria for multipartite higher-spin systems
我们开发的标准,以检测三类非局域性,已被证明由怀斯曼等人。[物理评论快报。98,140402(2007)]是不等价的:纠缠,EPR转向,和本地隐藏变量理论的失败。我们使用Cavalcanti等人的方法[Phys. Rev. Lett. 99,210405(2007)]的连续变量,以开发非定域性标准的任意自旋观测定义在离散希尔伯特空间。因此,该标准适用于多站点量子,即,系统的固定尺寸d,并采取不等式的形式。我们发现,当量子点数目N足够大时,优化的高关联非最大纠缠态在任意d下都可以违反检验局域隐变量的自旋矩不等式(贝尔不等式).另一方面,纠缠的自旋不等式被违反,从而检测纠缠的状态,为任意的d和N,并与违反,增加与N.我们表明,一个时刻纠缠不等式可以检测任意广义多体格林伯格-霍恩-蔡林格状态的纠缠。因为它们涉及原子系统的自然观测量,所以相关的自旋算符关联应该在被囚禁的超冷原子气体和离子阱中容易观察到。
The De Broglie-Bohm (DeBB)\cite{DeBB} Causal Quantum Mechanics played a crucial role in Bell's discovery \cite{Bell1964} that quantum mechanics violates EPR local reality \cite{EPR1935}, and also in Bell's search for an exact quantum mechanics. The experiments of Aspect et al \cite{Aspect1981} confirm quantum correlations between plane polarizations of two photons and violation of Bell's inequalities by a factor $\sqrt 2 $. I prove that similar experiments with elliptic polarizers can also show quantum violations of Bell's inequality by the same factor. I summarize our construction of a maxima…
In the derivation of local bound of a Bell's inequality, the response functions corresponding to the different outcomes of measurements are fixed by the relevant hidden variables irrespective of the fact if the measurement is unsharp. In the context of a recent result by Spekkens that tells even in an ontological model the unsharp observable cannot be assigned a deterministic response function, we derive a modified local bound of CHSH inequality in unsharp measurement scenario. We consider response function for a given POVM which is determined by the response functions of the relevant projecto…