Violation of local realism with freedom of choice

Abstract

Bell's theorem shows that local realistic theories place strong restrictions on observable correlations between different systems, giving rise to Bell's inequality which can be violated in experiments using entangled quantum states. Bell's theorem is based on the assumptions of realism, locality, and the freedom to choose between measurement settings. In experimental tests, "loopholes" arise which allow observed violations to still be explained by local realistic theories. Violating Bell's inequality while simultaneously closing all such loopholes is one of the most significant still open challenges in fundamental physics today. In this paper, we present an experiment that violates Bell's inequality while simultaneously closing the locality loophole and addressing the freedom-of-choice loophole, also closing the latter within a reasonable set of assumptions. We also explain that the locality and freedom-of-choice loopholes can be closed only within non-determinism, i.e. in the context of stochastic local realism.Comment: 12 pages, 3 figures, 2 tables, published online before print: http://www.pnas.org/content/early/2010/10/29/1002780107.abstrac

Bell violation using entangled photons without the fair-sampling assumption

“…The two other main assumptions include "locality" (10,11) and "freedom of choice" (12). Invoking any of these renders an experiment vulnerable to explanation by a local realistic theory.…”

Quantum Locality, Rings a Bell?: Bell’s Inequality Meets Local Reality and True Determinism

“…It is worth mentioning that the original experiments of Aspect [15,16] and the much improved experiment of Weihs [21] to address locality, do not resolve the freedom-of-choice loophole under the factuality scenario. Nor, for that matter, do the more recent experiments of Zeilinger's groups [22][23][24] with ever-increasing space-like separations between subsystems, under the scenario here presented. The reader may also wish to see [25].…”

Requirements for a loophole-free photonic Bell test using imperfect setting generators

“…For example, space-like separation of the pair generation from the setting choices eliminates the pair generation as a possible influence. This has been achieved in the experiments [18][19][20][21]. However, again it is not possible to exclude all possible influences in this way, because these could in principle extend arbitrarily far into the past.…”

“…Space-like separating the two outcome events enforces outcome independence, and space-like separating each party's independent setting choice event from the opposite party's outcome event enforces setting independence. In this way, the locality loophole is considered to have been closed for photons by the experiments [17][18][19][20][21], and with NV centers by the experiment [22].…”