2,641 research outputs found
Relative entropy of entanglement for certain multipartite mixed states
We prove conjectures on the relative entropy of entanglement (REE) for two
families of multipartite qubit states. Thus, analytic expressions of REE for
these families of states can be given. The first family of states are composed
of mixture of some permutation-invariant multi-qubit states. The results
generalized to multi-qudit states are also shown to hold. The second family of
states contain D\"ur's bound entangled states. Along the way, we have discussed
the relation of REE to two other measures: robustness of entanglement and
geometric measure of entanglement, slightly extending previous results.Comment: Single column, 22 pages, 9 figures, comments welcom
Multipartite quantum and classical correlations in symmetric n-qubit mixed states
We discuss how to calculate genuine multipartite quantum and classical
correlations in symmetric, spatially invariant, mixed -qubit density
matrices. We show that the existence of symmetries greatly reduces the amount
of free parameters to be optimized in order to find the optimal measurement
that minimizes the conditional entropy in the discord calculation. We apply
this approach to the states exhibited dynamically during a thermodynamic
protocol to extract maximum work. We also apply the symmetry criterion to a
wide class of physically relevant cases of spatially homogeneous noise over
multipartite entangled states. Exploiting symmetries we are able to calculate
the nonlocal and genuine quantum features of these states and note some
interesting properties.Comment: Close to published Versio
Multidimensional quantum entanglement with large-scale integrated optics
The ability to control multidimensional quantum systems is key for the
investigation of fundamental science and for the development of advanced
quantum technologies. Here we demonstrate a multidimensional integrated quantum
photonic platform able to robustly generate, control and analyze
high-dimensional entanglement. We realize a programmable bipartite entangled
system with dimension up to on a large-scale silicon-photonics
quantum circuit. The device integrates more than 550 photonic components on a
single chip, including 16 identical photon-pair sources. We verify the high
precision, generality and controllability of our multidimensional technology,
and further exploit these abilities to demonstrate key quantum applications
experimentally unexplored before, such as quantum randomness expansion and
self-testing on multidimensional states. Our work provides a prominent
experimental platform for the development of multidimensional quantum
technologies.Comment: Science, (2018
Operational approach to Bell inequalities: applications to qutrits
Bell inequalities can be studied both as constraints in the space of
probability distributions and as expectation values of multipartite operators.
The latter approach is particularly useful when considering outcomes as
eigenvalues of unitary operators. This brings the possibility of exploiting the
complex structure of the coefficients in the Bell operators. We investigate
this avenue of though in the known case of two outcomes, and find new Bell
inequalities for the cases of three outcomes and and parties. We
find their corresponding classical bounds and their maximum violation in the
case of qutrits. We further propose a novel way to generate Bell inequalities
based on a mapping from maximally entangled states to Bell operators and
produce examples for different outcomes and number of parties.Comment: 10 pages, no figures. A sign error in Eq.(10), appearing in the
published version, has been correcte
Measures of entanglement in multipartite bound entangled states
Bound entangled states are states that are entangled but from which no
entanglement can be distilled if all parties are allowed only local operations
and classical communication. However, in creating these states one needs
nonzero entanglement resources to start with. Here, the entanglement of two
distinct multipartite bound entangled states is determined analytically in
terms of a geometric measure of entanglement and a related quantity. The
results are compared with those for the negativity and the relative entropy of
entanglement.Comment: 5 pages, no figure; title change
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