We study a holographic model of an EPR pair at the boundary of bulk gravity, and use Bell inequality as a sharp test of entanglement. By revealing how Bell inequality is violated by gravity in the bulk, our study sheds light on the entanglement of the original ER=EPR conjecture.
Quantum Entanglement presents a paradox: measurements appear to influence distant systems instantaneously, violating the relativistic speed limit c. Standard interpretations accept "Non-Locality" as a fundamental feature of nature. Causal Latency Theory (CLT) proposes an alternative: Boundary Locality. We posit that 3D space is a holographic projection of a valid 2D Causal Horizon for fundamental forces. Entangled particles are not spatially connected links in the bulk, but distinct projections of the same addressable bit on the Horizon. We demonstrate that while information propagation through the bulk vacuum incurs a latency Δt=L/c, the path along the horizon surface is a null geodesic where proper time Δτ=0. This reinterprets Bell Inequality violations not as superluminal signaling, but as geometric shortcuts via the boundary. We validate this via simulation, predicting that entanglement fidelity will degrade as local acceleration (and the associated Rindler Horizon) intersects the correlation length. We propose the Centrifuge Bell Experiment and the Cosmic Switch satellite test to detect the anisotropy of quantum correlations relative to the Causal Rest Frame.
In the long-standing quest to reconcile gravity with quantum mechanics, profound connections have been unveiled between concepts traditionally pertaining to a quantum information theory, such as entanglement, and constitutive features of gravity, like holography. Developing and promoting these connections from the conceptual to the operational level unlock access to a powerful set of tools which can be pivotal toward the formulation of a consistent theory of quantum gravity. Here, we review recent progress on the role and applications of quantum informational methods, in particular tensor networks, for quantum gravity models. We focus on spin network states dual to finite regions of space, represented as entanglement graphs in the group field theory approach to quantum gravity, and illustrate how techniques from random tensor networks can be exploited to investigate their holographic properties. In particular, spin network states can be interpreted as maps from bulk to boundary, whose holographic behavior increases with the inhomogeneity of their geometric data (up to becoming proper quantum channels). The entanglement entropy of boundary states, which are obtained by feeding such maps with suitable bulk states, is then proved to follow a bulk area law with corrections due to the entanglement of the bulk state. We further review how exceeding a certain threshold of bulk entanglement leads to the emergence of a black hole-like region, revealing intriguing perspectives for quantum cosmology.
Bell's theorem revealed the fundamental incompatibility between the predictions of quantum mechanics and local realism. Bell inequality violations have since demonstrated quantum nonlocality using photons and internal states of massive particles, but never using their motional states. Here we report the first Bell inequality violation in the motional states of massive particles. Using momentum-entangled pairs of metastable helium atoms manipulated by matter-wave interferometry, we measure a Clauser-Horne-Shimony-Holt (CHSH) Bell parameter of S=2.52±0.17, violating the CHSH-Bell inequality (S≤2). Our work completes a long-standing objective in quantum atom optics by extending Bell tests from internal quantum variables to the external degrees of freedom of massive particles, opening a new regime for exploring quantum nonlocality in matter waves and for investigating the interplay between quantum mechanics and gravity.
Bell inequalities are intended to formulate mathematically the argument of the thought-experiment proposed by Einstein, Podolsky and Rosen (EPR) in the Einstein-Bohr Debate. Devised to test Bell inequalities against quantum mechanics for resolving the Einstein-Bohr debate, Bell experiments are purportedly modern versions of the EPR experiment. However, there exists a fatal logical flaw in Bell experiments. Because of the logical flaw, Bell experiments differ essentially from the EPR experiment, and quantum correlation in the EPR experiment is not "quantum entanglement" in Bell experiments; the latter is not physically meaningful. In addition to the logical flaw in Bell experiments, a physical constraint imposed on measuring individual quantum objects is violated by all Bell inequalities, which makes Bell inequalities physically meaningless. Unlike Bell experiments, the EPR experiment will not violate any physical constraint, and the EPR argument has no logical flaw. Consequently, the experimental invalidation of Bell inequalities is not evidence for falsifying the two fundamental hypotheses for scientific research, i.e., locality and realism, underlying the EPR experiment, and by no means can Bell experiments resolve the Einstein-Bohr debate. Stemming from abandoning either locality or realism or both, the so-called new applications of quantum mechanics, including various quantum information technologies, are all ineligible and doomed to failure, for they attempt to exploit physically meaningless "quantum superposition" or "quantum entanglement", treating them as physical resources "out there" in the real world.
EPR showed that two particles emitted from a source can be entangled by a shared wavefunction where two non-commuting observables (position, momentum) can be simultaneously real, leading to a contradiction with quantum mechanics (two non-commuting variables can not be simultaneously real). John Bell derived an inequality where any local hidden variables prediction is bounded and quantum mechanics can violate the inequality. Bell tests on correlated photon pairs showed a clear violation of the Bell inequality and agreement with quantum mechanics. This study revealed that the Bell inequality holds at any individual instances in a given system but it does not hold over the entire population. The Bell inequality is not an incompatibility criterion for local hidden variables vs quantum mechanics rather it is a criterion for an individual nature vs population dynamics. The nonlocality prediction given by wavefunction is a system approximation and local causality (photon polarization) provides a complete description of the Bell tests. The paper concludes with great satisfaction that the measurement of two correlated photons at a distance was a local cause (photon-filter interaction did not violate the special theory of relativity).
We discuss a few tests of the ER=EPR proposal. We consider certain conceptual issues as well as explicit physical examples that could be experimentally realized. In particular, we discuss the role of the Bell bounds, the large N limit, as well as the consistency of certain theoretical assumptions underlying the ER=EPR proposal. As explicit tests of the ER=EPR proposal we consider limits coming from the entropy-energy relation and certain limits coming from measurements of the speed of light as well as measurements of effective weights of entangled states. We also discuss various caveats of such experimental tests of the ER=EPR proposal.