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