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Local realism is the worldview in which physical properties of objects exist independently of measurement and where physical influences cannot travel faster than the speed of light. Bell's theorem states that this worldview is incompatible…

We propose a practical scheme to use photons from causally disconnected cosmic sources to set the detectors in an experimental test of Bell's inequality. In current experiments, with settings determined by quantum random number generators,…

Quantum Physics · Physics 2014-03-26 Jason Gallicchio , Andrew S. Friedman , David I. Kaiser

We report on an experiment demonstrating entanglement swapping of time-frequency entangled photons. We perform a frequency-resolved Bell-state measurement on the idler photons from two independent entangled photon pairs, which projects the…

Quantum Physics · Physics 2019-10-16 Sofiane Merkouche , Valérian Thiel , Alex O. C. Davis , Brian J. Smith

Certification of quantum nonlocality plays a central role in practical applications like device-independent quantum cryptography and random number generation protocols. These applications entail the challenging problem of certifying quantum…

Quantum Physics · Physics 2021-07-21 S. Gómez , D. Uzcategui , I. Machuca , E. S. Gómez , S. P. Walborn , G. Lima , D. Goyeneche

Opto- and electromechanical systems offer an effective platform to test quantum theory and its predictions at macroscopic scales. To date, all experiments presuppose the validity of quantum mechanics, but could in principle be described by…

Quantum Physics · Physics 2016-02-24 Sebastian G. Hofer , Konrad W. Lehnert , Klemens Hammerer

Nonlocal entanglement between pair-correlated particles is a highly counter-intuitive aspect of quantum mechanics, where measurement on one particle can instantly affect the other, regardless of distance. While the rigorous Bell's…

We propose a simple scheme for complete Bell-state measurement of photons using hyperentangled states - entangled in multiple degrees of freedom. In addition to hyperentanglement, our scheme requires only linear optics and single photon…

Quantum Physics · Physics 2009-11-10 S. P. Walborn , S. Pádua , C. H. Monken

A recent experiment presented, for photons, the first violation of a Bell inequality closing the fair-sampling loophole, i.e., without having to assume that the sample of measured photons fairly represents the entire ensemble. In this note,…

Quantum Physics · Physics 2013-07-25 Johannes Kofler , Sven Ramelow , Marissa Giustina , Anton Zeilinger

Entanglement is a critical resource used in many current quantum information schemes. As such entanglement has been extensively studied in two qubit systems and its entanglement nature has been exhibited by violations of the Bell…

Quantum Physics · Physics 2015-06-26 W. J. Munro , K. Nemoto , A. G. White

In single-particle or intraparticle entanglement, two degrees of freedom of a single particle, e.g., momentum and polarization of a single photon, are entangled. Single-particle entanglement (SPE) provides a source of non classical…

Quantum Physics · Physics 2021-01-04 M. Pasini , N. Leone , S. Mazzucchi , V. Moretti , D. Pastorello , L. Pavesi

We report the generation of polarization-entangled photons, using a quantum dot single photon source, linear optics and photodetectors. Two photons created independently are observed to violate Bell's inequality. The density matrix…

The study of entanglement in particle physics has been gathering pace in the past few years. It is a new field that is providing important results about the possibility of detecting entanglement and testing Bell inequality at colliders for…

High Energy Physics - Phenomenology · Physics 2024-12-20 Alan J. Barr , Marco Fabbrichesi , Roberto Floreanini , Emidio Gabrielli , Luca Marzola

I show that the photon pairs used in experimental tests of quantum non-locality based on Bell's theorem are not in the entangled quantum state. The correct quantum state of the ``entangled'' photon pairs is suggested. Two experiments for…

Quantum Physics · Physics 2007-05-23 Ruo Peng Wang

The question whether Quantum Mechanics describes all aspects of both the micro-world of elementary particles and living organisms adequately is still open. A Bell inequality test without locality and detection loopholes will deliver the…

Quantum Physics · Physics 2010-08-26 M. Stobińska , P. Horodecki , A. Buraczewski , R. W. Chhajlany , R. Horodecki , G. Leuchs

The experimental verification of quantum features, such as entanglement, at large scales is extremely challenging because of environment-induced decoherence. Indeed, measurement techniques for demonstrating the quantumness of multiparticle…

Quantum Physics · Physics 2013-02-26 Enrico Pomarico , Bruno Sanguinetti , Pavel Sekatski , Hugo Zbinden , Nicolas Gisin

We consider a Bell-like inequality performed using various instances of multi-photon entangled states to demonstrate that losses occurring after the unitary transformations used in the nonlocality test can be counteracted by enhancing the…

Quantum Physics · Physics 2012-06-22 Youngrong Lim , Mauro Paternostro , Jinhyoung Lee , Minsu Kang , Hyunseok Jeong

We first devise a scheme to perform a universal entangling gate via controlled collisions between pairs of atomic qubits trapped with optical tweezers. Second, we present a modification to this scheme to allow the preparation of atomic Bell…

Quantum Physics · Physics 2008-12-03 Nathan S. Babcock , Rene Stock , Mark G. Raizen , Barry C. Sanders

By amplifying photonic qubits it is possible to produce states that contain enough photons to be seen with a human eye, potentially bringing quantum effects to macroscopic scales [1]. In this paper we theoretically study quantum states…

Quantum Physics · Physics 2015-03-17 Pavel Sekatski , Bruno Sanguinetti , Enrico Pomarico , Nicolas Gisin , Christoph Simon

Quantum entanglement is the key resource for quantum information processing. Device-independent certification of entangled states is a long standing open question, which arouses the concept of self-testing. The central aim of self-testing…

We show a mechanism that projects a pair of neutral two-level atoms from an initially uncorrelated state to a maximally entangled state while they remain spacelike separated. The atoms begin both excited in a common electromagnetic vacuum,…

Quantum Physics · Physics 2009-11-13 Juan León , Carlos Sabín