[extropy-chat] Macroscale entanglement
thespike at satx.rr.com
Sat Apr 2 21:24:32 UTC 2005
Has this been mentioned here before?
"Crucial Role of Quantum Entanglement in Bulk Properties of Solids"
Authors: Caslav Brukner, Vlatko Vedral, Anton Zeilinger
Comments: 4 pages, 2 figures
We demonstrate that the magnetic susceptibility of strongly alternating
antiferromagnetic spin-1/2 chains is an entanglement witness. Specifically,
magnetic susceptibility of copper nitrate (CN) measured in 1963 (Berger et
al., Phys. Rev. 132, 1057 (1963)) cannot be described without presence of
entanglement. A detailed analysis of the spin correlations in CN as
obtained from neutron scattering experiments (Xu et al., Phys. Rev. Lett.
84, 4465 (2000)) provides microscopic support for this interpretation. We
present a quantitative analysis resulting in the critical temperature of 5K
in both, completely independent, experiments below which entanglement exists.
"The usual arguments against seeing entanglement on macroscopic scales is
that large objects contain large number of degrees of freedom that can
interact with environment thus inducing decoherence that ultimately lead to
a quantum-to-classical transition. Remarkably, macroscopic entanglement in
solids, that is, entanglement in the thermodynamical limit of infinite
large number of constituents of solids, was theoretically predicted to
exist even at moderately high temperatures [11, 12, 13, 14, 15]. Recently,
it was demonstrated that entanglement can even affect macroscopic
thermodynamical properties of solids [13, 16, 17, 18, 19, 20], such as its
magnetic susceptibility or heat capacity, albeit at very low temperature
(few milikelvin) and only for a special material system - the insulating
magnetic salt LiHoxY1Å|xF4 . This extraordinary result shows that
entanglement can have significant macroscopic effects. Here ... we analyse
experimental results of neutron scattering measurement of CN obtained in
2000  and show that they provide, for the first time, a direct
experimental demonstration of macroscopic entanglement in solids."
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