Consequences of recent loophole-free experiments on a relaxation of measurement independence (original) (raw)

Eberhardt's inequality and recent loophole-free experiments

2016

Recent experiments using innovative optical detectors and techniques have strongly increased the capacity of testing the violation of the Bell's inequalities in the Nature. Most of them have used the Eberhardt's inequality (EI) to close the"detection"loophole. Closing the"locality"loophole has been attempted by space-like separated detections and fast and random changes in the setting of the bases of observation. Also, pulsed pumping and time stamped data to close the"time-coincidence"loophole, and sophisticated statistical methods to close the"memory"loophole, have been used. In this paper, the meaning of the EI is reviewed. A simple hidden-variables theory based on a relaxation of the condition of"measurement independence", which was devised long ago for the Clauser-Horne-Shimony and Holt inequality, is adapted to the EI case. It is used here to evaluate the significance of the results of the new experiments, which are brie...

The EPR-B Paradox Resolution. Bell inequalities revisited

Journal of Physics: Conference Series, 2019

One of the Bell’s assumptions in the original derivation of his inequalities was the hypothesis of locality, i.e., the absence of the influence of two remote measuring instruments on one another. That is why violations of these inequalities observed in experiments are often interpreted as a manifestation of the nonlocal nature of quantum mechanics, or a refutation of a local realism. It is well known that the Bell’s inequality was derived in its traditional form, without resorting to the hypothesis of locality and without the introduction of hidden variables, the only assumption being that the probability distributions are nonnegative. This can therefore be regarded as a rigorous proof that the hypothesis of locality and the hypothesis of existence of the hidden variables not relevant to violations of Bell’s inequalities. The physical meaning of the obtained results is examined. Physical nature of the violation of the Bell inequalities is explained under new EPR-B nonlocality postul...

A loophole-free Bell's inequality experiment

1994

Abstract The proof of Nature's nonlocality through Bell-type experiments is a topic of longstanding interest. Nevertheless, no experiments performed thus far have avoided the so-called'detection loophole,'arising from low detector efficiencies and angular-correlation difficulties. In fact, most, if not all, of the systems employed to date can never close this loophole, even with perfect detectors. In addition, another loophole involving the non-rapid, non-random switching of various parameter settings exists in all past experiments.

Experimental violation of a Bell’s inequality in time with weak measurement

Nature Physics, 2010

The violation of Bell inequalities with two entangled and spatially separated quantum two-level systems (TLSs) is often considered as the most prominent demonstration that nature does not obey local realism. Under different but related assumptions of macrorealism-which macroscopic systems plausibly fulfil-Leggett and Garg derived a similar inequality for a single degree of freedom undergoing coherent oscillations and being measured at successive times. Here, we test such a 'Bell's inequality in time', which should be violated by a quantum TLS. Our TLS is a superconducting quantum circuit in which Rabi oscillations are continuously driven while it is continuously and weakly measured. The time correlations present at the detector output agree with quantum-mechanical predictions and violate the Leggett-Garg inequality by five standard deviations.

Observations of Bell Inequality Violations with Causal Isolation between Source and Detectors

Entropy

We report the experimental observations of Bell inequality violations (BIV) in entangled photons causally separated by a rotating mirror. A Foucault mirror gating geometry is used to causally isolate the entangled photon source and detectors. We report an observed BIV of CHSH-S=2.30±0.07>2.00. This result rules out theories that explain correlations with traveling communication between source and detectors, including super-luminal and instantaneous communication.

Time-resolved measurement of Bell inequalities and the coincidence loophole

Physical Review A, 2012

We report an Einstein-Podolsky-Rosen-Bohm experiment with a pulsed source of entangled pairs of photons, recording the time of arrival of the pulses and of the detection of each single photon. This allows varying the parameters of the analysis (as the size of the time coincidence window) at will after the experiment has ended. Among other results, we present the measurement of the time variation of the Clauser-Horne-Shimony-Holt parameter during the pulse. The obtained results close (or at least impose new and tight restrictions to) the last loophole that remains open in the tests of quantum mechanics vs local realism (the so-called coincidence loophole).

The Bell inequalities and the joint measurement of incompatible observables

Foundations of Physics Letters, 1992

On the basis of a theory of the joint nonideal (or inaccurate) measurement of incompatible observables an experiment is proposed in which all four observables that are involved in the Bell inequalities are measured jointly. It is demonstrated that the difference between violation and satisfaction ofthe Bell inequalities can be accounted for in a local way.

On Epr Paradox, Bell's Inequalities and Experiments that Prove Nothing

Old and New Concepts of Physics, 2008

This article shows that the there is no paradox. Violation of Bell's inequalities should not be identified with a proof of non locality in quantum mechanics. A number of past experiments is reviewed, and it is concluded that the experimental results should be re-evaluated. The results of the experiments with atomic cascade are shown not to contradict the local realism. The article points out flaws in the experiments with down-converted photons. The experiments with neutron interferometer on measuring the "contextuality" and Bell-like inequalities are analyzed, and it is shown that the experimental results can be explained without such notions. Alternative experiment is proposed to prove the validity of local realism.

Optical tests of Bell’s inequalities not resting upon the absurd fair sampling assumption,(2004)

A simple local hidden-variables model is exhibited which reproduces the results of all performed tests of Bell´s inequalities involving optical photon pairs. For the old atomic-cascade experiments, like As-pect´s, the model agrees with quantum mechanics even for ideal setups. For more recent experiments, using parametric down-converted photons, the agreement occurs only for actual experiments, involving low efficiency detectors. Arguments are given against the fair sampling assumption, currently combined with the results of the experiments in order to claim a contradiction with local realism. New tests are proposed which are able to discriminate between quantum mechanics and a restricted, but appealing, family of local hidden-variables models. Such tests require detectors with efficiencies just above 20%.

Bell's inequality for a single measurement within EPR paradox

The essence of the EPR paradox on an example of measuring polarization of photon pairs or of spin 1/2 particles is demonstrated. The common view of the two photons or particles state radiated by a source is presented. The simplest Bell's inequalities for a specific hidden parameter are derived. An experiment to study whether a photon and a particle with their polarizations are preexistent before measurements or not is considered.