scholarly journals Relativistic independence bounds nonlocality

2019 ◽  
Vol 5 (4) ◽  
pp. eaav8370 ◽  
Author(s):  
Avishy Carmi ◽  
Eliahu Cohen
Keyword(s):  
Quantum Mechanics ◽  
Quantum Correlations ◽  
Physical Principle ◽  
Quantum Nonlocality ◽  
Measuring Instruments ◽  
Uncertainty Relations ◽  
The Past ◽  
Nonlocal Correlations

If nature allowed nonlocal correlations other than those predicted by quantum mechanics, would that contradict some physical principle? Various approaches have been put forward in the past two decades in an attempt to single out quantum nonlocality. However, none of them can explain the set of quantum correlations arising in the simplest scenarios. Here, it is shown that generalized uncertainty relations, as well as a specific notion of locality, give rise to both familiar and new characterizations of quantum correlations. In particular, we identify a condition, relativistic independence, which states that uncertainty relations are local in the sense that they cannot be influenced by other experimenters’ choices of measuring instruments. We prove that theories with nonlocal correlations stronger than the quantum ones do not satisfy this notion of locality, and therefore, they either violate the underlying generalized uncertainty relations or allow experimenters to nonlocally tamper with the uncertainty relations of their peers.

scholarly journals Causation does not explain contextuality

Quantum ◽  
2018 ◽  
Vol 2 ◽  
pp. 63 ◽  
Author(s):  
Sally Shrapnel ◽  
Fabio Costa
Keyword(s):  
Quantum Mechanics ◽  
Causal Structure ◽  
Quantum Correlations ◽  
Global Constraints ◽  
Local Constraints ◽  
The Past ◽  
Interpretations Of Quantum Mechanics ◽  
The World ◽  
Non Local ◽  
Initial States

Realist interpretations of quantum mechanics presuppose the existence of elements of reality that are independent of the actions used to reveal them. Such a view is challenged by several no-go theorems that show quantum correlations cannot be explained by non-contextual ontological models, where physical properties are assumed to exist prior to and independently of the act of measurement. However, all such contextuality proofs assume a traditional notion of causal structure, where causal influence flows from past to future according to ordinary dynamical laws. This leaves open the question of whether the apparent contextuality of quantum mechanics is simply the signature of some exotic causal structure, where the future might affect the past or distant systems might get correlated due to non-local constraints. Here we show that quantum predictions require a deeper form of contextuality: even allowing for arbitrary causal structure, no model can explain quantum correlations from non-contextual ontological properties of the world, be they initial states, dynamical laws, or global constraints.

QUANTUM MECHANICS AND THE ROLE OF TIME: ARE QUANTUM SYSTEMS MARKOVIAN?

2012 ◽  
Vol 26 (27n28) ◽  
pp. 1243005 ◽  
Author(s):  
THOMAS DURT
Keyword(s):  
Quantum Mechanics ◽  
Quantum Systems ◽  
Quantum Nonlocality ◽  
Border Line ◽  
The Past ◽  
Open Questions ◽  
The Status ◽  
Alternative Theories ◽  
Time In Quantum Mechanics

The predictions of the Quantum Theory have been verified so far with astonishingly high accuracy. Despite of its impressive successes, the theory still presents mysterious features such as the border line between the classical and quantum world, or the deep nature of quantum nonlocality. These open questions motivated in the past several proposals of alternative and/or generalized approaches. We shall discuss in the present paper alternative theories that can be infered from a reconsideration of the status of time in quantum mechanics. Roughly speaking, quantum mechanics is usually formulated as a memory free (Markovian) theory at a fundamental level, but alternative, nonMarkovian, formulations are possible, and some of them can be tested in the laboratory. In our paper we shall give a survey of these alternative proposals, describe related experiments that were realized in the past and also formulate new experimental proposals.

scholarly journals QUANTUM NONLOCAL BOXES EXHIBIT STRONGER DISTILLABILITY

2013 ◽  
Vol 28 (17) ◽  
pp. 1330012
Author(s):  
PETER HØYER ◽  
JIBRAN RASHID
Keyword(s):  
Quantum Correlations ◽  
Status Quo ◽  
Quantum Nonlocality ◽  
Semidefinite Program ◽  
Adaptive Protocol ◽  
Nonlocal Correlations ◽  
The Status ◽  
Strong Motivation ◽  
Repeated Applications ◽  
Nonlocal Box

The hypothetical nonlocal box (NLB) proposed by Popescu and Rohrlich allows two spatially separated parties, Alice and Bob, to exhibit stronger than quantum correlations. If the generated correlations are weak, they can sometimes be distilled into a stronger correlation by repeated applications of the NLB. Motivated by the limited distillability of NLBs, we initiate here a study of the distillation of correlations for nonlocal boxes that output quantum states rather than classical bits (qNLBs). We propose a new protocol for distillation and show that it asymptotically distills a class of correlated quantum nonlocal boxes to the value [Formula: see text], whereas in contrast, the optimal non-adaptive parity protocol for classical nonlocal boxes asymptotically distills only to the value 3.0. We show that our protocol is an optimal non-adaptive protocol for 1, 2 and 3 qNLB copies by constructing a matching dual solution for the associated primal semidefinite program (SDP). We conclude that qNLBs are a stronger resource for nonlocality than NLBs. The main premise that develops from this conclusion is that the NLB model is not the strongest resource to investigate the fundamental principles that limit quantum nonlocality. As such, our work provides strong motivation to reconsider the status quo of the principles that are known to limit nonlocal correlations under the framework of qNLBs rather than NLBs.

scholarly journals CLASSICAL, QUANTUM AND SUPERQUANTUM CORRELATIONS

2012 ◽  
Vol 27 (01n03) ◽  
pp. 1345011
Author(s):  
GIANCARLO GHIRARDI ◽  
RAFFAELE ROMANO
Keyword(s):  
Quantum Mechanics ◽  
Quantum Correlations ◽  
Quantum Limit ◽  
Nonlocal Correlations ◽  
Classical Quantum ◽  
Physical Principles

A deeper understanding of the origin of quantum correlations is expected to allow a better comprehension of the physical principles underlying quantum mechanics. In this work, we reconsider the possibility of devising "crypto-nonlocal theories", using a terminology firstly introduced by Leggett. We generalize and simplify the investigations on this subject which can be found in the literature. At their deeper level, such theories allow nonlocal correlations which can overcome the quantum limit.

Relational Blockworld and Quantum Mechanics

2018 ◽  
Author(s):  
Michael Silberstein ◽  
W.M. Stuckey ◽  
Timothy McDevitt
Keyword(s):  
Quantum Mechanics ◽  
Measurement Problem ◽  
Quantum Nonlocality ◽  
Global Constraints ◽  
Quantum Superposition ◽  
Delayed Choice ◽  
Counterfactual Definiteness ◽  
Main Thread ◽  
Block Universe ◽  
Contextual Emergence

The main thread of chapter 4 introduces some of the major mysteries and interpretational issues of quantum mechanics (QM). These mysteries and issues include: quantum superposition, quantum nonlocality, Bell’s inequality, entanglement, delayed choice, the measurement problem, and the lack of counterfactual definiteness. All these mysteries and interpretational issues of QM result from dynamical explanation in the mechanical universe and are dispatched using the authors’ adynamical explanation in the block universe, called Relational Blockworld (RBW). A possible link between RBW and quantum information theory is provided. The metaphysical underpinnings of RBW, such as contextual emergence, spatiotemporal ontological contextuality, and adynamical global constraints, are provided in Philosophy of Physics for Chapter 4. That is also where RBW is situated with respect to retrocausal accounts and it is shown that RBW is a realist, psi-epistemic account of QM. All the relevant formalism for this chapter is provided in Foundational Physics for Chapter 4.

scholarly journals Beyond Causal Explanation: Einstein’s Principle Not Reichenbach’s

Entropy ◽  
2021 ◽  
Vol 23 (1) ◽  
pp. 114
Author(s):  
Michael Silberstein ◽  
William Mark Stuckey ◽  
Timothy McDevitt
Keyword(s):  
Quantum Mechanics ◽  
Quantum Information ◽  
Causal Explanation ◽  
Causal Structure ◽  
Minkowski Spacetime ◽  
Physical Principle ◽  
Causal Principle ◽  
Complete Rejection ◽  
Epr Correlations ◽  
Tsirelson Bound

Our account provides a local, realist and fully non-causal principle explanation for EPR correlations, contextuality, no-signalling, and the Tsirelson bound. Indeed, the account herein is fully consistent with the causal structure of Minkowski spacetime. We argue that retrocausal accounts of quantum mechanics are problematic precisely because they do not fully transcend the assumption that causal or constructive explanation must always be fundamental. Unlike retrocausal accounts, our principle explanation is a complete rejection of Reichenbach’s Principle. Furthermore, we will argue that the basis for our principle account of quantum mechanics is the physical principle sought by quantum information theorists for their reconstructions of quantum mechanics. Finally, we explain why our account is both fully realist and psi-epistemic.

scholarly journals Demonstrating the power of quantum computers, certification of highly entangled measurements and scalable quantum nonlocality

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Elisa Bäumer ◽  
Nicolas Gisin ◽  
Armin Tavakoli
Keyword(s):  
Quantum Computer ◽  
Outcome Measurement ◽  
Bell State ◽  
Bell Inequalities ◽  
Quantum Correlations ◽  
Entanglement Swapping ◽  
Quantum Nonlocality ◽  
Quantum Computers ◽  
Classical Models ◽  
Quantum Phenomena

AbstractIncreasingly sophisticated quantum computers motivate the exploration of their abilities in certifying genuine quantum phenomena. Here, we demonstrate the power of state-of-the-art IBM quantum computers in correlation experiments inspired by quantum networks. Our experiments feature up to 12 qubits and require the implementation of paradigmatic Bell-State Measurements for scalable entanglement-swapping. First, we demonstrate quantum correlations that defy classical models in up to nine-qubit systems while only assuming that the quantum computer operates on qubits. Harvesting these quantum advantages, we are able to certify 82 basis elements as entangled in a 512-outcome measurement. Then, we relax the qubit assumption and consider quantum nonlocality in a scenario with multiple independent entangled states arranged in a star configuration. We report quantum violations of source-independent Bell inequalities for up to ten qubits. Our results demonstrate the ability of quantum computers to outperform classical limitations and certify scalable entangled measurements.

WHITE NOISE ANALYSIS: SOME APPLICATIONS IN COMPLEX SYSTEMS, BIOPHYSICS AND QUANTUM MECHANICS

2012 ◽  
Vol 26 (29) ◽  
pp. 1230014 ◽  
Author(s):  
CHRISTOPHER C. BERNIDO ◽  
M. VICTORIA CARPIO-BERNIDO
Keyword(s):  
Quantum Mechanics ◽  
Probability Density Function ◽  
Complex Systems ◽  
White Noise ◽  
Noise Analysis ◽  
Social Systems ◽  
White Noise Analysis ◽  
The Past ◽  
White Noise Calculus ◽  
With Memory

The white noise calculus originated by T. Hida is presented as a powerful tool in investigating physical and social systems. Combined with Feynman's sum-over-all histories approach, we parameterize paths with memory of the past, and evaluate the corresponding probability density function. We discuss applications of this approach to problems in complex systems and biophysics. Examples in quantum mechanics with boundaries are also given where Markovian paths are considered.

scholarly journals Free Will in Human Behavior and Physics

2020 ◽  
Author(s):  
Vasil Dinev Penchev
Keyword(s):  
Quantum Mechanics ◽  
Quantum Information ◽  
Free Will ◽  
Human Behavior ◽  
Physical World ◽  
Classical Physics ◽  
Quantum Bit ◽  
The Past ◽  
The Mean ◽  
The One

If the concept of “free will” is reduced to that of “choice” all physical world share the latter quality. Anyway the “free will” can be distinguished from the “choice”: The “free will” involves implicitly a certain goal, and the choice is only the mean, by which the aim can be achieved or not by the one who determines the target. Thus, for example, an electron has always a choice but not free will unlike a human possessing both. Consequently, and paradoxically, the determinism of classical physics is more subjective and more anthropomorphic than the indeterminism of quantum mechanics for the former presupposes certain deterministic goal implicitly following the model of human freewill behavior. Quantum mechanics introduces the choice in the fundament of physical world involving a generalized case of choice, which can be called “subjectless”: There is certain choice, which originates from the transition of the future into the past. Thus that kind of choice is shared of all existing and does not need any subject: It can be considered as a low of nature. There are a few theorems in quantum mechanics directly relevant to the topic: two of them are called “free will theorems” by their authors (Conway and Kochen 2006; 2009). Any quantum system either a human or an electron or whatever else has always a choice: Its behavior is not predetermined by its past. This is a physical law. It implies that a form of information, the quantum information underlies all existing for the unit of the quantity of information is an elementary choice: either a bit or a quantum bit (qubit).

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