Bell and Beyond: Exploring the Limits of Nonlocality

Claudio Garola

Bradley G. Christensen, Yeong-Cherng Liang, Nicolas Brunner +2 more

Nonlocality is arguably among the most counterintuitive phenomena predicted by quantum theory.In recent years, the development of an abstract theory of nonlocality has brought a much deeper understanding of the subject, revealing a rich and complex phenomenon.In the current work, we present a systematic experimental exploration of the limits of quantum nonlocality.Using a versatile and high-fidelity source of pairs of polarization-entangled photons, we explore the boundary of quantum correlations, demonstrate the counterintuitive effect of more nonlocality with less entanglement, present the most nonlocal correlations ever reported, and achieve quantum correlations requiring the use of complex qubits.All of our results are in remarkable agreement with quantum predictions, and thus represent a thorough test of quantum theory.Pursuing such an approach is nevertheless highly desirable, as any deviation may provide evidence of new physics beyond the quantum model.

Bradley Christensen, Yeong-Cherng Liang, Nicolas Brunner +2 more

Nonlocality is arguably among the most counterintuitive phenomena predicted by quantum theory. In recent years, the development of an abstract theory of nonlocality has brought a much deeper understanding of the subject, revealing a rich and complex phenomenon. In the current work, we present a systematic experimental exploration of the limits of quantum nonlocality. Using a versatile and high-fidelity source of pairs of polarization-entangled photons, we explore the boundary of quantum correlations, demonstrate the counterintuitive effect of more nonlocality with less entanglement, present the most nonlocal correlations ever reported, and achieve quantum correlations requiring the use of complex qubits. All of our results are in remarkable agreement with quantum predictions, and thus represent a thorough test of quantum theory. Pursuing such an approach is nevertheless highly desirable, as any deviation may provide evidence of new physics beyond the quantum model.

Federico Laudisa

André Saugo Mazzari

Avishy Y. Carmi, Daniel Moskovich

A central theme in quantum mechanics is nonlocality, which states that a pair of quantum systems which are shown not to be physically interacting may nevertheless be impossible to describe as independent entities. Quantum theory, however, forbids nonlocal correlations beyond a certain limit. Why is nature only so nonlocal and not more? Approaching the question from the direction of statistics and statistical inference, we identify a statistical no-signaling principle which states that no information may pass through a disconnected channel. We show this principle to be equivalent to the Tsirelson bound on nonlocality for the Bell--CHSH inequality.