53 research outputs found
Time-ordering Dependence of Measurements in Teleportation
We trace back the phenomenon of "delayed-choice entanglement swapping" as it
was realized in a recent experiment to the commutativity of the projection
operators that are involved in the corresponding measurement process. We also
propose an experimental set-up which depends on the order of successive
measurements corresponding to noncommutative projection operators. In this case
entanglement swapping is used to teleport a quantum state from Alice to Bob,
where Bob has now the possibility to examine the noncommutativity within the
quantum history.Comment: 20 pages, 7 figures; v2; formalism of isometries elaborately
discussed, some changes in formulas, figure and reference added; typos
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Entanglement witnesses and geometry of entanglement of two--qutrit states
We construct entanglement witnesses with regard to the geometric structure of
the Hilbert--Schmidt space and investigate the geometry of entanglement. In
particular, for a two--parameter family of two--qutrit states that are part of
the magic simplex we calculate the Hilbert--Schmidt measure of entanglement. We
present a method to detect bound entanglement which is illustrated for a
three--parameter family of states. In this way we discover new regions of bound
entangled states. Furthermore we outline how to use our method to distinguish
entangled from separable states.Comment: 23 pages, 8 figure
Residual entanglement of accelerated fermions is not nonlocal
We analyze the operational meaning of the residual entanglement in
non-inertial fermionic systems in terms of the achievable violation of the
Clauser-Horne-Shimony-Holt (CHSH) inequality. We demonstrate that the quantum
correlations of fermions, which were previously found to survive in the
infinite acceleration limit, cannot be considered to be non-local. The
entanglement shared by an inertial and an accelerated observer cannot be
utilized for the violation of the CHSH inequality in case of high
accelerations. Our results are shown to extend beyond the single mode
approximation commonly used in the literature.Comment: 5 pages, 3 figures; v2: minor changes, reference and section headers
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