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Bell tests are of profound statistical nature. Besides physical considerations, the proper understanding of their implications should involve detailed statistical analyses. In this regard, recent works have shown that their consequences and…

Quantum Physics · Physics 2025-06-10 Alfredo Luis

Although it's widely believed that gravity should have a quantum nature like every other force, the conceptual obstacles to constructing a quantum theory of gravity compel us to explore other perspectives. Gravity is not like any other…

General Relativity and Quantum Cosmology · Physics 2024-07-30 Jonathan Oppenheim

This text is an introduction to an operational outlook on Bell inequalities, which has been very fruitful in the past few years. It has lead to the recognition that Bell tests have their own place in applied quantum technologies, because…

Quantum Physics · Physics 2015-06-19 Valerio Scarani

The logical foundations of Bell's inequality are reexamined. We argue that the form of the reality condition that underpins Bell's inequality comes from the requirement of solving the quantum measurement problem. Hence any violation of…

Quantum Physics · Physics 2008-02-19 John V. Corbett , Dipankar Home

In this essay based on 0907.2939, we argue that the emergence of classically connected spacetimes is intimately related to the quantum entanglement of degrees of freedom in a non-perturbative description of quantum gravity. Disentangling…

High Energy Physics - Theory · Physics 2025-07-08 Mark Van Raamsdonk

General relativity is incomplete because it cannot describe quantum effects of space-time. The complete theory of quantum gravity is not yet known and to date no observational evidence exists that space-time is quantized. However, in most…

General Relativity and Quantum Cosmology · Physics 2018-07-17 Sabine Hossenfelder , Ricardo Gallego Torromé

Bell-inequality violations reveal the presence of quantum correlations between two particles that have interacted and then separated. Their generalisation to quantum fields is necessary to study a number of field-theoretic setups, such as…

Quantum Physics · Physics 2022-07-28 Llorenç Espinosa-Portalés , Vincent Vennin

Spacetime inversion symmetries such as parity and time reversal play a central role in physics, but they are usually treated as global symmetries. In quantum gravity there are no global symmetries, so any spacetime inversion symmetries must…

High Energy Physics - Theory · Physics 2025-04-25 Daniel Harlow , Tokiro Numasawa

We investigate the interplay and connections between symmetry properties of equations, the interpretation of coordinates, the construction of observables, and the existence of physical relativity principles in spacetime theories. Using the…

General Relativity and Quantum Cosmology · Physics 2009-06-30 Hans Westman , Sebastiano Sonego

Although time is one of our most intuitive physical concepts, its understanding at the fundamental level is still an open question in physics. For instance, time in quantum mechanics and general relativity are two distinct and incompatible…

Quantum Physics · Physics 2021-01-27 Eduardo O. Dias

General relativity is a background-independent theory of a dynamical classical spacetime geometry. Quantum theory is formulated in a classical spacetime, as an intrinsically probabilistic, contextual theory of non-classical, interfering…

General Relativity and Quantum Cosmology · Physics 2026-04-22 Tristan Hübsch , Djordje Minic

We exploit the reparametrization symmetry of a relativistic free particle to impose a gauge condition which upon quantization implies space-time noncommutativity. We show that there is an algebraic map from this gauge back to the standard…

High Energy Physics - Theory · Physics 2009-11-10 A. Pinzul , A. Stern

We report on a Bell experiment with space-like separation assuming that the measurement time is related to gravity-induced state reduction. Two energy-time entangled photons are sent through optical fibers and directed into unbalanced…

Quantum Physics · Physics 2010-05-12 D. Salart , A. Baas , J. A. W. van Houwelingen , N. Gisin , H. Zbinden

In ordinary, non-relativistic, quantum physics, time enters only as a parameter and not as an observable: a state of a physical system is specified at a given time and then evolved according to the prescribed dynamics. While the state can,…

Quantum Physics · Physics 2013-02-13 Joseph Fitzsimons , Jonathan Jones , Vlatko Vedral

A generic implication of incorporating gravitational effects in the analysis of quantum measurements is the existence of a zero-point length of spacetime. This requires an inherently non-local description of spacetime, beyond the usual one…

General Relativity and Quantum Cosmology · Physics 2023-05-17 Dawood Kothawala

Einstein, Podolsky and Rosen (EPR) showed that it is possible to predict with certainty the value of a property without disturbing the object in question. In contrast, Quantum Mechanics (QM) holds that if different measurement setups cannot…

Quantum Physics · Physics 2024-08-23 Bart Jongejan

This paper provides a systematic analysis of Bell experiments from the relational perspective, demonstrating that the apparent ``nonlocality'' of quantum mechanics stems from a problematic application of relativistic principles rather than…

Quantum Physics · Physics 2025-09-11 Jan van Neerven , Marijn Waaijer

We provide a brief overview into recent tests of gravity, focusing on its foundational spacetime symmetries. In particular, we work with an agnostic, effective field-theory framework, named the Standard-Model Extension, that allows for…

General Relativity and Quantum Cosmology · Physics 2023-05-24 Kellie O'Neal-Ault

In recent years several ideas for experimental searches of effects induced by quantum properties of space-time have been discussed. Some of these ideas concern the role in quantum spacetime of the ordinary Lorentz symmetry of classical flat…

Astrophysics · Physics 2007-05-23 Giovanni Amelino-Camelia

Which nonlocal correlations can be obtained, when a party has access to more than one subsystem? While traditionally nonlocality deals with spacelike separated parties, this question becomes important with quantum technologies that connect…

Quantum Physics · Physics 2023-09-04 Moisés Bermejo Morán , Alejandro Pozas-Kerstjens , Felix Huber