Interpretation of the Experiments on Bell's Inequality

The conceptual scheme of the optical polarization experiments on Bell's inequality is discussed. By invoking the distinction between the concepts of state preparation and measumment in quantum mechanics, it is argued that Bell's theorem is not applicable to this class of experiments in the way it is generally done. Consequently, by considering the specific features of the measurements performed hitherto, it is also shown that a local approach can yield the same theoretical prediction as the nonlocal quantum interpretation, even in the absence of other experimental loopholes.     

Violations of Bell's Inequality in Synchronized Hyperchaos

Motivated by a parallel between quantum cryptography and chaos synchronization cryptography, we construct a Bell's inequality for a pair of synchronously coupled variable-order Generalized Rossler Systems, with arbitrarily binarized final states. In the infinite-order limit, although dynamical parameters cannot be extracted from the coupling signal in finite time, the inequality is violated, as with entangled quantum states. The violations are weaker than in quantum theory, vanishing as the differences between corresponding parameters of the coupled systems become small. The fact that Bell's inequality can be violated for a pair of classical systems that are not discernibly connected supports the possibility of a realist interpretation of quantum mechanics.     

Quantum entanglement and quantum nonlocality for N-photon entangled states

Quantum entanglement and quantum nonlocality of N-photon entangled states |psi_{N m}rangle=C_m[cosgamma|N-mrangle₁|mrangle₂ +e^{iθ_m}singamma|mrangle₁|N-mrangle₂] and their superpositions are studied. We point out that the relativephase θ_m affects the quantum nonlocality but not the quantumentanglement for the state |psi_{N m}rangle. We show thatquantum nonlocality can be controlled and manipulated by adjustingthe state parameters of |psi_{N m}rangle, superpositioncoefficients, and the azimuthal angles of the Bell operator. Wealso show that the violation of the Bell inequality can reach itsmaximal value under certain conditions. It is found that quantumsuperpositions based on |psi_{N m}rangle can increase theamount of entanglement, and give more ways to reach the maximalviolation of the Bell inequality.     

Simplified Scheme for Test of Quantum Nonlocality Without Using Bell Inequality

A simplified scheme is proposed for the test of quantum nonlocality of the type described by Hardy [Phys.Rev.Left.71 (1993) 1665].In the scheme two appropriately prepared atoms are simultaneously sent through a cavity and dispersively interact with the cavity field.Then state-selective measurements are performed on these atoms,which may reveal quantum nonlocality without using Bell inequality.We also propose a simple scheme for the generation of multi-atom entangled states.``     

Entanglement of a Single Spin-1 Object: An Example of Ubiquitous Entanglement

Using a single spin-1 object as an example, we discuss a recent approach to quantum entanglement. [A.A. Klyachko and A.S. Shumovsky, J. Phys: Conf. Series 36, 87 (2006), E-print quant-ph/0512213]. The key idea of the approach consists in presetting of basic observables in the very definition of quantum system. Specification of basic observables defines the dynamic symmetry of the system. Entangled states of the system are then interpreted as states with maximal amount of uncertainty of all basic observables. The approach gives purely physical picture of entanglement. In particular, it separates principle physical properties of entanglement from inessential. Within the model example under consideration, we show relativity of entanglement with respect to dynamic symmetry and argue existence of single-particle entanglement. A number of physical examples are considered.      

Comparison between local Kolmogorovian models and Bell's inequality

The conditions on the relative frequencies of coincidence between the measurements on two physical systems are deduced, in the particular case of four different directions, from Kolmogorovian probability and the Gutkowski and Valdes-Franco computational method. These conditions are compared with those imposed by Bell's inequality. It is proved that Bell's inequality is a necessary but not a sufficient condition for local Kolmogorovian probability. The further assumptions to be added to Bell's inequality, in order to prove the equivalence with local Kolmogorovian probability, are studied. The connection with the results obtained by other authors on the subject is discussed.     

2022年诺贝尔物理学奖的科学内涵辨识

2022年的诺贝尔物理学奖,被一些人误解为证明了量子纠缠现象。实际上,包括爱因斯坦本人都承认量子纠缠,关键在于如何诠释。今年诺贝尔物理学奖的价值在于这几位物理学家以无可争辩的实验事实,证明了基于定域隐变量的贝尔不等式是不对的。目前的一些介绍文字,没有认真解释量子力学在理论上是如何批驳贝尔不等式的,同时虽对量子纠缠的物理价值多有阐述,但对其哲学意义却鲜有评述,对社会上滥用纠缠概念缺少直接批判和阐释。文章希望在这两方面有所补充。     

广义GHZ态的纠缠与非定域性

对GHZ态与W态叠加的三粒子广义GHZ态,用Svetlichny不等式,给出了其非定域性的解析表达式.用数值计算方法讨论了纠缠与非定域性之间的关系.关键词：广义GHZ态剩余纠缠Svetlichny不等式非定域性     

Comments on “determinism,realism, and Stapp's 1985 proof of nonlocality”

An earlier argument by the author, that Stapp's 1985 proof of quantum locality contains an implicit element of realism, is elaborated. Refuted thereby is Clifton's criticism that the author's argument was based on a misinterpretation of counterfactual analysis.     

An Intermediate-Energy Experimental Test of Bell's Inequalty with Recoil Polarimeters

To date there has been only one test for local reality which used fermions. Lamehi-Rachti and Mittig measured correlated protons with a recoil polarimeter at Saclay. We discuss this experiment and survey the published criticism. We then propose an experiment involving a 500 MeV electron beam on a ³He target. The two protons in the ³He nucleus originally have their spins anti-aligned. The spins of the ejected protons can be measured with a recoil polarimeter and the correlation function obtained, which will be a good test of Local Reality and Bell's inequality.     

Quantum discord dynamics of two qubits in single-mode cavities

The dynamics of quantum discord for two identical qubits in two independent single-mode cavities and a common single-mode cavity are discussed. For the initial Bell state with correlated spins, while the entanglement sudden death can occur, the quantum discord vanishes only at discrete moments in the independent cavities and never vanishes in the common cavity. Interestingly, quantum discord and entanglement show opposite behavior in the common cavity, unlike in the independent cavities. For the initial Bell state with anti-correlated spins, quantum discord and entanglement behave in the same way for both independent cavities and a common cavity. It is found that the detunings always stabilize the quantum discord.     

Entanglement in 2DEG systems: towards a detection loophole-free test of Bell's inequality

We make use of the intrinsic noiseless and lossless aspect of an electron source in a 2DEG system to implement a new test of Bell's inequality. The generated entanglement can be tested by two-particle interferometry. Preparation and detection schemes of two complete sets of Bell states are given. A novel type of Bell's inequality is then derived in terms of noise correlation measurements. The characteristics of the electron source are essential to exhibit a violation. This electron system could close the detection efficiency loophole.     

Identification of All Hardy-Type Correlations for Two Photons or Particles with Spin 1/2

By using an alternative, equivalent form of the CHSH inequality and making extensive use of the experimentally testable property of physical locality we determine the 64 different Bell-type inequalities (each one involving four joint probabilities) into which Hardy's nonlocality theorem can be cast. This allows one to identify all the two-qubit correlations which can exhibit Hardy-type nonlocality.     

三光子GHZ态中不同Bell型不等式的实验研究

实验研究了Bell不等式、Mermin不等式和Svetlichny不等式在GHZ态中对定域实在论结果的破坏. 采用目标态密度矩阵的方法给出了实验制备的GHZ态的保真度, 得到了三个不等式在GHZ态中的测量值. 实验结果表明, 三个Bell型不等式在同一个状态下对定域实在论结果破坏程度不同, 在量子密钥分配中可以选择合适的非定域性描述方式考察所用信道的安全性.     

A scheme to realize time-bin entanglement between two photons that never interacted

We propose a scheme of entangling two photons from two separated sources. Our proposal which is inspired by the time-bin entanglement developed recently, provides a novel alternative for revealing contradiction between quantum nonlocality and local realism based on two independent single photon sources.