Quantum Coherence, Coherent Information and Information Gain in Quantum Measurement

A measurement is deemed successful, if one can maximize the information gain by the measurement apparatus. Here, we ask if quantum coherence of the system imposes a limitation on the information gain during quantum measurement. First, we argue that the information gain in a quantum measurement is nothing but the coherent information or the distinct quantum information that one can send from the system to apparatus. We prove that the maximum information gain from a pure state, using a mixed apparatus is upper bounded by the initial coherence of the system. Further, we illustrate the measurement scenario in the presence of environment. We argue that the information gain is upper bounded by the entropy exchange between the system and the apparatus. Also, to maximize the information gain, both the initial coherence of the apparatus, and the final entanglement between the system and apparatus should be maximum. Moreover, we find that for a fixed amount of coherence in the final apparatus state the more robust apparatus is, the more will be the information gain.Comment: 6 Pages, Comments are welcom

Local, nonlocal quantumness and information theoretic measures

It has been suggested that there may exist quantum correlations that go beyond entanglement. The existence of such correlations can be revealed by quantum discord, but not by the conventional measure of entanglement. We argue that a state displays quantumness that can be of local and nonlocal origin. The physical quantity such as the quantum discord probes not only the nonlocal quantumness but also the local quantumness, such as the "local superposition". This can be a reason why such measures are non-zero when there is no entanglement. We consider a generalized version of the Werner state to demonstrate the interplay of local quantumness, nonlocal quantumness, and classical mixedness of a state.Comment: 7 pages, 8 figures. Title changed. Accepted for publication in IJQ

Complementarity of Quantum Correlations in Cloning and Deleting of Quantum State

We quantify the amount of correlation generated between two different output modes in the process of im- perfect cloning and deletion processes. We use three different measures of correlations and study their role in determining the fidelity of the cloning and deletion. We obtain a bound on the total correlation generated in the successive process of cloning and deleting operations. This displays a new kind of complementary relationship between the quantum correlation required in generating a copy of a quantum state and the amount of correlation required in bringing it back to the original state by deleting and vice versa. Our result shows that better we clone (delete) a state, more difficult it will be to bring the state back to its original form by the process of deleting (cloning).Comment: 10 pages, 3 figures, Accepted in Physical Review

Exploring the possibility of enhancing the figure-of-merit ( >> 2) of Na0.74_{0.74}CoO2_{2}: A combined experimental and theoretical study

Search of new thermoelectric (TE) materials with high \textit{figure-of-merit} (ZT) is always inspired the researcher in TE field. Here, we present a combined experimental and theoretical study of TE properties of Na$_{0.74}$CoO$_{2}$ compound in high-temperature region. The experimental Seebeck coefficient (S) is found to vary from 64 to 118 $\mu$V/K in the temperature range $300-620$ K. The positive values of S are indicating the dominating p-type behaviour of the compound. The observed value of thermal conductivity ($\kappa$) is $\sim$ 2.2 W/m-K at 300 K. In the temperature region $300-430$ K, the value of $\kappa$ increases up to $\sim$ 2.6 W/m-K and then decreases slowly till 620 K with the corresponding value of $\sim$ 2.4 W/m-K. We have also carried out the theoretical calculations and the best matching between experimental and calculated values of transport properties are observed in spin-polarized calculation within DFT+\textit{U} by chosen \textit{U} = 4 eV. The maximum calculated value of ZT is found to be $\sim$ 0.67 at 1200 K for p-type conduction. Our computational study suggests that the possibility of n-type behaviour of the compound which can lead to a large value of ZT at higher temperature region. Electron doping of $\sim$ 5.1$\times$10$^{20}$ cm$^{-3}$ is expected to give rise the high ZT value of $\sim$ 2.7 at 1200 K. Using these temperature-dependent ZT values, we have calculated the maximum possible values of efficiency ($\eta$) of thermoelectric generator (TEG) made by p and n-type Na$_{0.74}$CoO$_{2}$. The present study suggests that one can get the efficiency of a TE cell as high as $\sim$ 11$\%$ when the cold and hot end temperature are fixed at 300 K and 1200 K, respectively. Such high values of ZT and efficiency suggest that Na$_{0.74}$CoO$_{2}$ can be used as a potential candidate for high-temperature TE applications

Improvement of flowability, compressibility and dissolution of aceclofenac by emulsion solvent diffusion with polyethylene glycol.

Objetivo: El objetivo detrás de este estudio es mejorar la tasa de compresión, la fluidez, packability y la disolución de aceclofenaco mediante la preparación de cristales esféricos utilizando el método cuasi emulsión de disolvente de difusión.Material y Método: Aglomerados esféricos de aceclofenac se prepararon con acetona, diclorometano y ac. HCl 0,1 N que actúan como buen disolvente, líquido aglutinante y mal disolvente respectivamente. En este último caso se añadieron diferentes cantidades de propilenglicol 6000.Resultados: Los aglomerados esféricos obtenidos se caracterizaron por tener una mayor fragmentación y menor recuperación elástica. En comparación con los cristales originales de aceclofenac, los aglomerados tienen mejores características de tamaño de partícula, fluidez, compactabilidad, empaquetado, solubilidad y velocidad de disolución lo que les hace más adecuados para compresión. Los estudios de difracción por rayos X y calorimetría diferencial de barrido mostraron una pequeña tendencia a formar amorfos durante la recristalización del aceclofenac aunque el estudio mediante espectroscopía infrarroja de Fournier no mostró cambios químicos.Conclusión: La presente investigación mejora de las propiedades de tabletas y characteristics de disolución de aceclofenaco.Aim: The objective behind this study is to improve the compressibility, flowability, packability and dissolution rate of aceclofenac by preparing spherical crystals using quasi emulsion solvent diffusion method.Materials and Method: Spherical agglomerates of aceclofenac were effectively prepared using acetone, dichloromethane and 0.1 N HCl as good solvent, bridging liquid and poor solvent respectively with different concentrations of polyethylene glycol 6000 in poor solvent.Results: Prepared agglomerates were spherical with enhanced fragmentation and less elastic recovery. Particle size, flowability, compactibility, packability, solubility and dissolution rate of agglomerates were preferably improved for direct compression compared with raw crystal of aceclofenac. X-ray powder diffraction and differential scanning calorimetry study indicated slight amorphization of drug during recrystallization but not associated with any chemical transition indicated by Fourier transforms infrared spectra.Conclusion: The present research improved tableting properties and dissolution characteristics of aceclofenac