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

GREEN SYNTHESIS AND CHARACTERIZATION OF SILVER NANOPARTICLES USING EXTRACT OF Anisomeles malabarica (L.) AND EVALUATION OF ITS ANTIMICROBIAL ACTIVITIES

The phytochemical analysis carried out on the aqueous leaves extract of Anisomeles malabarica showed the presence of a maximum number of phytochemicals. The green synthesis of SNPs was done successfully using aqueous leaves extract of A.malabarica. Primary confirmation of color change from pale yellow to brown color was observed at 420nm recorded by UV- Visible spectroscopy and detailed characterization was carried out using UV-Visible spectroscopy, XRD, SEM. Present investigation also suggests that the green synthesized SNPs are exerting in vitro toxic effects on human microbial pathogens. Antibacterial studies of SNPs were highly attractive with different inhibition zone capacity when compared with aqueous leaves extract. Similarly Antifungal studies of SNPs also showed significant antifungal activity against the fungus when compared with aqueous leaves extract. The zone of inhibition formed is maximum in Aspergillus niger and showed best antifungal activity when compared with Candida albicans

Interplay of quantum stochastic and dynamical maps to discern Markovian and non-Markovian transitions

It is known that the dynamical evolution of a system, from an initial tensor product state of system and environment, to any two later times, t1,t2 (t2>t1), are both completely positive (CP) but in the intermediate times between t1 and t2 it need not be CP. This reveals the key to the Markov (if CP) and nonMarkov (if it is not CP) avataras of the intermediate dynamics. This is brought out here in terms of the quantum stochastic map A and the associated dynamical map B -- without resorting to master equation approaches. We investigate these features with four examples which have entirely different physical origins (i) a two qubit Werner state map with time dependent noise parameter (ii) Phenomenological model of a recent optical experiment (Nature Physics, 7, 931 (2011)) on the open system evolution of photon polarization. (iii) Hamiltonian dynamics of a qubit coupled to a bath of $N$ qubits and (iv) two qubit unitary dynamics of Jordan et. al. (Phys. Rev. A 70, 052110 (2004)) with initial product states of qubits. In all these models, it is shown that the positivity/negativity of the eigenvalues of intermediate time dynamical B map determines the Markov/non-Markov nature of the dynamics.Comment: 6 pages, 5 figures, considerably extended version of arXiv:1104.456