2,662 research outputs found
Is composite noise necessary for sudden death of entanglement?
The finite time disentanglement or entanglement sudden death, when only one
part of the composite system is subjected to a single noise, is examined. While
it is shown that entanglement sudden death can occur when a part of the
entangled mixed state is subjected to either amplitude noise or phase noise,
local action of either of them does not cause entanglement sudden death in pure
entangled states. In contrast, depolarizing noise is shown to have an abilitiy
to cause sudden death of entanglement even in pure entangled states, when only
one part of the state is exposed to it. The result is illustrated through the
action of different noisy environments individually on a single qubit of the
so-called X class of states and an arbitrary two-qubit pure state.Comment: 6 pages, 4 figures; Version 3: Accepted for publication in the
Results in Physics: Comments welcom
Quantumness of correlations and entanglement
Generalized measurement schemes on one part of bipartite states, which would
leave the set of all separable states insensitive are explored here to
understand quantumness of correlations in a more general perspecitve. This is
done by employing linear maps associated with generalized projective
measurements. A generalized measurement corresponds to a quantum operation
mapping a density matrix to another density matrix, preserving its positivity,
hermiticity and traceclass. The Positive Operator Valued Measure (POVM) --
employed earlier in the literature to optimize the measures of
classical/quatnum correlations -- correspond to completely positive (CP) maps.
The other class, the not completely positive (NCP) maps, are investigated here,
in the context of measurements, for the first time. It is shown that that such
NCP projective maps provide a new clue to the understanding the quantumness of
correlations in a general setting. Especially, the separability-classicality
dichotomy gets resolved only when both the classes of projective maps (CP and
NCP) are incorporated as optimizing measurements. An explicit example of a
separable state -- exhibiting non-zero quantumn discord when possible
optimizing measurements are restricted to POVMs -- is re-examined with this
extended scheme incorporating NCP projective maps to elucidate the power of
this approach.Comment: 14 pages, no figures, revision version, Accepted for publication in
the Special Issue of the International Journal of Quantum Information devoted
to "Quantum Correlations: entanglement and beyond
Review Manavari Manitarkal Novel
Suryakanthan's novel 'Manavari manitarkal' won the Ilakkiya cintaṉai and Akhilan Novel Memorial Prize. Novels are generally the records of the creators' own experiences. All writers belong to a particular social group or section in historical and social trends. They truly reflect the nature of this community or Surroundings and man's relation to it. Suryakanthan has been creating earthy novelties in the field of Tamil literature for many years, especially in the Kongu country background. Many analysts welcome the distinction of local novelties. There are certain customs and speech patterns for a region. There are also some unique problems for the people of a particular region. Hence in Kongu is called a local novelty. A life of innovation is precious. In fact, Suryakanthan's ''Manavari manitarkal” is proof that the story is based on the universality of the writers, living in the world, seeing, and hearing
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