02.70.+a Theories alternative to quantum mechanics

Postquantum Steering

Date: 
2015-05-11 - 2015-11-04
Author(s): 

Ana Belén Sainz, Nicolas Brunner, Daniel Cavalcanti, Paul Skrzypczyk, Tamás Vértesi

Reference: 

Phys. Rev. Lett. 115, 190403

The discovery of postquantum nonlocality, i.e., the existence of nonlocal correlations that are stronger than any quantum correlations but nevertheless consistent with the no-signaling principle, has deepened our understanding of the foundations of quantum theory.

Almost quantum correlations

Date: 
2014-06-20 - 2015-02-20
Author(s): 

Miguel Navascués, Yelena Guryanova, Matty J. Hoban, Antonio Acín

Reference: 

Nature Communications 6, Article number: 6288

Quantum theory is not only successfully tested in laboratories every day but also constitutes a robust theoretical framework: small variations usually lead to implausible consequences, such as faster-than-light communication. It has even been argued that quantum theory may be special among possible theories.

Ideal negative measurements in quantum walks disprove theories based on classical trajectories

Date: 
2015-01-20
Author(s): 

Carsten Robens, Wolfgang Alt, Dieter Meschede, Clive Emary, Andrea Alberti

Reference: 

Phys. Rev. X 5, 011003 (2015)

We report on a stringent test of the nonclassicality of the motion of a massive quantum particle, which propagates on a discrete lattice. Measuring temporal correlations of the position of single atoms performing a quantum walk, we observe a $6\sigma$ violation of the Leggett-Garg inequality. Our results rigorously excludes (i.e., falsifies) any explanation of quantum transport based on classical, well-defined trajectories.

Monogamies of correlations and amplification of randomness

Date: 
2013-08-12 - 2013-12-05
Author(s): 

R. Augusiak, M. Demianowicz, M. Pawłowski, J. Tura, A. Acín

Reference: 

arXiv:1307.6390 [quant-ph]

Physical principles constrain the way nonlocal correlations can be distributed among parties in a Bell experiment. Here, we show that in any no-signalling theory the amount of violation of a certain class of Bell inequalities tightly bounds the knowledge that an external observer can gain about outcomes of any single measurement performed by the parties.

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