177 research outputs found
Genuine Multipartite Entanglement in the -Photon Decay of Positronium
The electron-positron annihilation into two photons is a standard technology
in medicine to observe e.g. metabolic processes in human bodies. A new
tomograph will provide the possibility to observe not only direct
annihilations but also the photons from the decay of ortho-positronium
atoms formed in the body. We show in this contribution that the three-photon
state with respect to polarisation degrees of freedom depends on the angles
between the photons and exhibits various specific entanglement features. In
particular genuine multipartite entanglement, a type of entanglement involving
all degrees of freedoms, is subsistent if the positronium was in a definite
spin eigenstate. Remarkably, when all spin eigenstates are mixed equally,
entanglement --and even stronger genuine multipartite entanglement-- survives.
Due to a "\textit{symmetrization}" process, however, -type of
entanglement remains whereas -type of entanglement vanishes. The survival
of particular entanglement properties in the mixing scenario may make it
possible to extract quantum information in form of distinct entanglement
features, e.g., from metabolic processes in human bodies.Comment: 9 pages, 5 figure
Can a spontaneous collapse in flavour oscillations be tested at KLOE?
Why do we never see a table in a superposition of here and there? This
problem gets a solution by so called collapse models assuming the collapse as a
genuinely physical process. Here we consider two specific collapse models and
apply them to systems at high energies, i.e. flavour oscillating neutral meson
systems. We find on one hand a potentially new interpretation of the decay
rates introduced by hand in the standard formalism and on the other hand that
these systems at high energies constrain by experimental data the possible
collapse scenarios.Comment: To appear in the proceedings of the KLOE-2 Workshop on e+e- collision
physics at 1 GeV, 26-28 October 2016, INFN - Laboratori Nazionali di
Frascati, Ital
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