AAWSAP DIRD, The Space Communication Implications of Quantum Entanglement and Nonlocality, March 2010

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Appendix: Glossary
Basis: In quantum mechanics, a choice of an observable quantity that may be
complementary to another variable, so that both cannot be measured at the same time.
An example is the choice of measuring position, which prevents the simultaneous
measurement of momentum. In EPR experiments, one must choose a polarization basis
(for example, linear polarization that may be either vertical or horizontal). Since both
circular polarization and 45° left/right polarization are linear superpositions of
vertical/horizontal polarization, they may not be measured simultaneously. In quantum
mechanics, the measurement causes the wave function to collapse to a particular basis
value, excluding other possible values.
Bell's Theorem: A mathematical proof by John S. Bell (Reference 8) demonstrating
that in a polarization-based EPR experiment, the fal loff of correlations as the basis
angle of a polarization measurement is changed is qualitatively different, as predicted
by local hidden-variable theories and by standard quantum mechanics. In particular,
local hidden-variable theories predict a linear falloff, while quantum mechanics predicts
a quadratic falloff. This difference in predictions is represented as an inequality in
measurement intensity ratios that all local hidden variable theories must satisfy, while
quantum mechanics does not. Tests of these predictions have been found to agree with
quantum mechanics and to falsify local hidden-variable theories.
Bilking Paradox: A type of back-in-time communication paradox in which an
inconsistent causal loop is created. A well-known example is the Grandmother Paradox,
a time-travel scenario from science fiction in which a time traveler travels to the past
and kills his grandmother before she had children. The question then arises, How could
he have been born if his grandmother had no children? Several works in the physics
literature (Reference 17, 18) have concluded that such trans-temporal bilking is
impossible, that nature will not permit inconsistent timelike loops, and that it is more
likely that some apparatus will fail than that a "bilk" of nature could be achieved .
Causality: The observation, which is regarded as a law of physics, that a cause must
precede its effects as viewed in any and all reference frames. Sometimes referred to as
"Cause and Effect" or "the Law of Cause and Effect."
Correlations: The mathematical connection between two variables or two measured
quantities. As an example, in an EPR measurement, the basis polarization of one
photon is selected, the basis polarization of the twin entangled photon is varied, and
the coincidence counting rate versus varied angle is measured to establish the
correlation between the two polarizations.
Coherence: Describes whether two waves (for example, those arriving at a pair of slits
or at a detector) have a definite phase relation (in which case they are completely
coherent), have a random phase relation (in which case they are completely
incoherent), or have something in between.
Coherence-Entanglement Complementarity: The theoretical expectation and
experimental observation (Reference 15) that perfect coherence and perfect
entanglement cannot be achieved for an entangled pair of photons at the same time.
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