4,034 research outputs found
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 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
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