105 research outputs found
\u3ci\u3eMy dreamy manifesto under the starry sky - cometward\u3c/i\u3e
Attention: This manifesto has in itself a magic power and it can finally refute the communist manifesto (1847/48) and its successors in the form of communist states. It burns a peaceful campfire
From contextuality of a single photon to realism of an electromagnetic wave
Violations of Bell inequalities have been an incontestable indicator of
non-classicality since the seminal paper by John Bell. However, recent claims
of Bell inequalities violations with classical light have cast some doubts on
their significance as hallmarks of non-classicality. Here, we challenge those
claims. The crux of the problem is that such classical experiments simulate
quantum probabilities with intensities of classical fields. However, fields
intensities measurements are radically different from single-photon detections,
which are primitives of any genuine Bell experiment. We show that this
fundamental difference between field intensities measurements and single photon
detections shifts the classical bound of relevant Bell inequalities to its
algebraic limit, leaving no place for their violations.Comment: 11 pages, 4 figure
On safe post-selection for Bell tests with ideal detectors: Causal diagram approach
Reasoning about Bell nonlocality from the correlations observed in
post-selected data is always a matter of concern. This is because conditioning
on the outcomes is a source of non-causal correlations, known as a selection
bias, rising doubts whether the conclusion concerns the actual causal process
or maybe it is just an effect of processing the data. Yet, even in the
idealised case without detection inefficiencies, post-selection is an integral
part of experimental designs, not least because it is a part of the
entanglement generation process itself. In this paper we discuss a broad class
of scenarios with post-selection on multiple spatially distributed outcomes. A
simple criterion is worked out, called the all-but-one principle, showing when
the conclusions about nonlocality from breaking Bell inequalities with
post-selected data remain in force. Generality of this result, attained by
adopting the high-level diagrammatic tools of causal inference, provides safe
grounds for systematic reasoning based on the standard form of multipartite
Bell inequalities in a wide array of entanglement generation schemes, without
worrying about the dangers of selection bias. In particular, it can be applied
to post-selection defined by single-particle events in each detection chanel
when the number of particles in the system is conserved.Comment: 16 pages, 9 figure
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