45 research outputs found
A Refutation of Bell's Theorem
Bell's Theorem was developed on the basis of considerations involving a
linear combination of spin correlation functions, each of which has a distinct
pair of arguments. The simultaneous presence of these different pairs of
arguments in the same equation can be understood in two radically different
ways: either as `strongly objective,' that is, all correlation functions
pertain to the same set of particle pairs, or as `weakly objective,' that is,
each correlation function pertains to a different set of particle pairs.
It is demonstrated that once this meaning is determined, no discrepancy
appears between local realistic theories and quantum mechanics: the discrepancy
in Bell's Theorem is due only to a meaningless comparison between a local
realistic inequality written within the strongly objective interpretation (thus
relevant to a single set of particle pairs) and a quantum mechanical prediction
derived from a weakly objective interpretation (thus relevant to several
different sets of particle pairs).Comment: RevTex4, 9 pages. Extended and entirely revised version. A talk given
at the Vaxjo conference, Sweden; Nov. 2000. Submited to J. Math. Phy
Violation of Bell Inequalities as a Violation of Fair Sampling in Threshold Detectors
Photomultiplier tubes and avalanche photodiodes, which are commonly used in
quantum optic experiments, are sometimes referred to as threshold detectors
because, in photon counting mode, they cannot discriminate the number of
photoelectrons initially extracted from the absorber in the detector. We argue
that they can be called threshold detectors on more account than that. We point
out that their their functioning principle relies on two thresholds that are
usually thought unimportant individually in the context of EPR-Bell discussion.
We show how the combined effect of these threshold can lead to a significant
sampling selection bias in the detection of pairs of pulses, resulting in an
apparent violation of Bell inequalities.Comment: 11 pages, 8 figures, FPP5 conference, Vaxjo (Sweden) August 200
A Fair Sampling Test for Ekert Protocol
We propose a local scheme to enhance the security of quantum key distribution
in Ekert protocol (E91). Our proposal is a fair sampling test meant to detect
an eavesdropping attempt that would use a biased sample to mimic an apparent
violation of Bell inequalities. The test is local and non disruptive: it can be
unilaterally performed at any time by either Alice or Bob during the production
of the key, and together with the Bell inequality test.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett
Frequency and phase relations of entangled photons observed by a two-photon interference experiment
An entangled photon experiment has been performed with a large variation of
the temperature of the non-linear crystal generating the entangled pair by
spontaneous downconversion. The photon pairs are separated by a nonpolarizing
beamsplitter, and the polarization modes are mixed by half wave plates. The
correlation function of the coincidences is studied as a function of the
temperature. In the presence of a narrow interference filter we observe that
the correlation changes between -1 and +1 about seven times within a
temperature interval of about 30 degrees C. We show that the common simplified
single-mode pair representation of entangled photons is insufficient to
describe the results, but that the biphoton description that includes frequency
and phase details gives close to perfect fit with experimental data for two
different choices of interference filters. We explain the main ideas of the
underlying physics, and give an interpretation of the two-photon amplitude
which provides an intuitive understanding of the effect of changing the
temperature and inserting interference filters.Comment: arXiv admin note: text overlap with arXiv:1309.108