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Witnessing continuous-variable Bell nonlocality is a challenging endeavor, but Bell himself showed how one might demonstrate this nonlocality. Though Bell nearly showed a violation using the CHSH inequality with sign-binned…

Quantum Physics · Physics 2016-01-20 James Schneeloch , Samuel H. Knarr , Daniel J. Lum , John C. Howell

Optimizing the brightness of a spontaneous parametric down conversion (SPDC) source is an important task for many quantum information applications. We investigate the optimal focusing conditions to maximize the number of photons produced in…

Quantum Physics · Physics 2023-09-29 Lorenzo Coccia , Alberto Santamato , Giuseppe Vallone , Paolo Villoresi

Spontaneous parametric down-conversion (SPDC) is a reliable platform for entanglement generation. Routinely, a coherent laser beam is an essential prerequisite for pumping the nonlinear crystal. Here we break this barrier to generate…

Quantum Physics · Physics 2022-11-09 Wuhong Zhang , Diefei Xu , Lixiang Chen

We present theoretical and experimental study of preparing maximally entangled two-photon polarization states, or Bell states, using femtosecond pulse pumped spontaneous parametric down-conversion (SPDC). First, we show how the inherent…

Quantum Physics · Physics 2009-11-07 Yoon-Ho Kim , Maria V. Chekhova , Sergei P. Kulik , Morton H. Rubin , Yanhua Shih

We propose and analyze a protocol for observing a violation of the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality using two spatially separated Bose-Einstein condensates (BECs). To prepare the Bell-correlated state, spin-changing…

A long-standing problem in the foundations of quantum mechanics is to identify a physical principle that explains why algebraically maximal violations of Bell inequalities can generally not be achieved in Nature. One recently proposed…

Quantum Physics · Physics 2026-03-24 Lionel J. Dmello , David Gross

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

Nonlocal quantum realizations, certified by the violation of a Bell inequality, are core resources for device-independent quantum information processing. Although proof-of-principle experiments demonstrating device-independent quantum…

It is well-known that in certain scenarios weakly entangled states can generate stronger nonlocal effects than their maximally entangled counterparts. In this paper, we consider violations of the CHSH Inequality when one party has…

Quantum Physics · Physics 2018-06-13 Daniel Dilley , Eric Chitambar

The famous Clauser-Horne-Shimony-Holt (CHSH) inequality certifies a quantum violation, by a factor $\sqrt{2}$, of correlations predicted by the classical view of the world in the simplest possible nontrivial measurement setup (two systems…

Quantum Physics · Physics 2017-12-25 Ben Li

We study optimal conditions for violation of the Clauser-Horne-Shimony-Holt form of the Bell inequality in the presence of decoherence and measurement errors. We obtain all detector configurations providing the maximal Bell inequality…

Superconductivity · Physics 2017-03-28 Abraham G. Kofman

The only information available about an alleged source of entangled quantum states is the amount $S$ by which the Clauser-Horne-Shimony-Holt (CHSH) inequality is violated: nothing is known about the nature of the system or the measurements…

Quantum Physics · Physics 2009-12-19 C. -E. Bardyn , T. C. H. Liew , S. Massar , M. McKague , V. Scarani

In Bell experiments, one problem is to achieve high enough photodetection to ensure that there is no possibility of describing the results via a local hidden-variable model. Using the Clauser-Horne inequality and a two-photon non-maximally…

Quantum Physics · Physics 2022-03-16 Adan Cabello , Jan-Åke Larsson

In this paper, we investigate the critical efficiency of detectors to observe Bell nonlocality using multiple copies of the maximally entangled two-qubit state carried by a single pair of particles, such as hyperentangled states, and the…

Quantum Physics · Physics 2023-02-09 István Márton , Erika Bene , Tamás Vértesi

Sources of entangled photon pairs are a key component in both fundamental tests of quantum theory and practical applications such as quantum key distribution and quantum computing. In this work, we describe and characterize a source of…

Quantum Physics · Physics 2013-10-03 Terence E. Stuart , Joshua A. Slater , Felix Bussieres , Wolfgang Tittel

The Horodecki criterion provides a necessary and sufficient condition for a two-qubit state to be able to manifest Bell nonlocality via violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality. It requires, however, the assumption that…

Quantum Physics · Physics 2022-01-10 Michael J. W. Hall , Shuming Cheng

Bell inequalities are an important tool in device-independent quantum information processing because their violation can serve as a certificate of relevant quantum properties. Probably the best known example of a Bell inequality is due to…

We analyze Bell inequalities violations in photonic experiments for which the measurement apparatuses are restricted to homodyne measurements. Through numerical optimization of the Clauser-Horne-Shimony-Holt inequality over homodyne…

Quantum Physics · Physics 2024-02-05 Enky Oudot , Gaël Massé , Xavier Valcarce , Antonio Acín

Bell correlations are usually formulated for an ideal spin singlet, for which the Bell--CHSH combination reaches the maximal quantum value \(B=-2\sqrt{2}\), independent of detector separation. Here we derive Bell correlations from a more…

Quantum Physics · Physics 2026-05-26 Ju Gao , Fang Shen

Entanglement does not always require one particle per party. It was predicted some thirty years ago that a single photon traversing a beam splitter could violate a Bell inequality. Although initially debated, single-photon nonlocality was…

Quantum Physics · Physics 2026-04-16 Daniel Kun , Teodor Strömberg , Borivoje Dakić , Philip Walther , Lee A. Rozema