146 research outputs found
Delayed choice for entanglement swapping
Two observers (Alice and Bob) independently prepare two sets of singlets.
They test one particle of each singlet along an arbitrarily chosen direction
and send the other particle to a third observer, Eve. At a later time, Eve
performs joint tests on pairs of particles (one from Alice and one from Bob).
According to Eve's choice of test and to her results, Alice and Bob can sort
into subsets the samples that they have already tested, and they can verify
that each subset behaves as if it consisted of entangled pairs of distant
particles, that have never communicated in the past, even indirectly via other
particles.Comment: 7 pages, LaTeX, to appear in special issue of J. Modern Optic
What's Wrong with these Observables?
An imprecise measurement of a dynamical variable (such as a spin component)
does not, in general, give the value of another dynamical variable (such as a
spin component along a slightly different direction). The result of the
measurement cannot be interpreted as the value of any observable that has a
classical analogue.Comment: submitted to Foundations of Physic
Opposite momenta lead to opposite directions
When a particle decays into two fragments, the wavefunctions of the latter
are spherical shells with expanding radii. In spite of this spherical symmetry,
the two particles can be detected only in opposite directions.Comment: 3 pages LaTeX, submitted to American Journal of Physic
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