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Suhas D.P.,Poornaprajna Institute of Scientific Research | Raghu A.V.,Poornaprajna Institute of Scientific Research | Jeong H.M.,University of Ulsan | Aminabhavi T.M.,Poornaprajna Institute of Scientific Research
RSC Advances | Year: 2013

Graphene-loaded sodium alginate (NaAlg) nanocomposite membranes have been prepared to enhance the pervaporation (PV) dehydration of isopropanol. The effect of graphene loading on the physico-chemical properties, micro-morphology and barrier performance of the derived nanocomposite membranes was investigated as a function of temperature and feed water composition of the isopropanol mixture. The interaction of graphene with the NaAlg matrix as well as water and isopropanol seems to influence the thermal, kinetic and Arrhenius activation energy parameters. At the lowest concentration of graphene, the membrane performance was optimum with a permeance value of 3122 GPU and a selectivity of 4623 for a 10 wt.% water containing feed mixture at 30 °C. Flory-Huggins theory could explain the polymer-solvent interaction as well as equilibrium swelling; both of these affected the membrane performance. © 2013 The Royal Society of Chemistry.


Savanur K.,Raman Research Institute | Srikanth R.,Raman Research Institute | Srikanth R.,Poornaprajna Institute of Scientific Research
Scientometrics | Year: 2010

Collaborative coefficient (CC) is a measure of collaboration in research, that reflects both the mean number of authors per paper as well as the proportion of multi-authored papers. Although it lies between the values 0 and 1, and is 0 for a collection of purely single-authored papers, it is not 1 for the case where all papers are maximally authored, i. e., every publication in the collection has all authors in the collection as co-authors. We propose a simple modification of CC, which we call modified collaboration coefficient (or MCC, for short), which improves its performance in this respect. © 2009 Akadémiai Kiadó, Budapest, Hungary.


Omkar S.,Poornaprajna Institute of Scientific Research | Srikanth R.,Poornaprajna Institute of Scientific Research | Srikanth R.,Raman Research Institute | Banerjee S.,IIT
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

Characterizing noisy quantum processes is important to quantum computation and communication (QCC), since quantum systems are generally open. To date, all methods of characterization of quantum dynamics (CQD), typically implemented by quantum process tomography, are off-line, i.e., QCC and CQD are not concurrent, as they require distinct state preparations. Here we introduce a method, "quantum error correction based characterization of dynamics," in which the initial state is any element from the code space of a quantum error correcting code that can protect the state from arbitrary errors acting on the subsytem subjected to unknown dynamics. The statistics of stabilizer measurements, with possible unitary preprocessing operations, are used to characterize the noise, while the observed syndrome can be used to correct the noisy state. Our method requires at most 2(4n-1) configurations to characterize arbitrary noise acting on n qubits. © 2015 American Physical Society.


Rao B.R.,Poornaprajna Institute of Scientific Research | Srikanth R.,Poornaprajna Institute of Scientific Research | Chandrashekar C.M.,Chennai Mathematical Institute | Banerjee S.,Indian Institute of Technology Jodhpur
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

Noisy quantum walks are studied from the perspective of comparing their quantumness as defined by two popular measures, measurement-induced disturbance (MID) and quantum discord (QD). While the former has an operational definition, unlike the latter, it also tends to overestimate nonclassicality because of a lack of optimization over local measurements. Applied to quantum walks, we find that MID, while acting as a loose upper bound on QD, still tends to reflect correctly trends in the behavior of the latter. However, there are regimes where its behavior is not indicative of nonclassicality: in particular, we find an instance where MID increases with the application of noise, where we expect a reduction of quantumness. © 2011 American Physical Society.


Sarkar S.,Poornaprajna Institute of Scientific Research
Physica B: Condensed Matter | Year: 2012

Atoms trapped in micro-cavities and interacting through the exchange of virtual photons can be modeled as an anisotropic Heisenberg spin-1/2 lattice. We do the quantum field theoretical study of such a system using the Abelian bosonization method followed by the renormalization group analysis. An infinite order BerezinskiiKosterlizThouless transition is replaced by second order XY transition even when an infinitesimal anisotropy in exchange coupling is introduced. We predict a quantum phase transition between the photonic Coulomb blocked induce Mott insulating and photonic superfluid phases due to detuning between the cavity and laser frequency. A large detuning favors the photonic superfluid phase. We also perform the analysis of Jaynes and Cumming Hamiltonian to support the results of quantum field theoretical study. © 2011 Elsevier B.V. All rights reserved.


Sarkar S.,Poornaprajna Institute of Scientific Research
Physica B: Condensed Matter | Year: 2015

Abstract We present the results of low lying collective mode of coupled optical cavity arrays. We derive the Dirac equation for this system and explain the existence of Majorana fermion mode in the system. We present quite a few analytical relations between the Rabi frequency oscillation and the atom-photon coupling strength to explain the different physical situation of our study and also the condition for massless collective mode in the system. We present several analytical relations between the Dirac spinor field, order and disorder operators for our systems. We also show that the Luttinger liquid physics is one of the intrinsic concepts in our system. © 2015 Published by Elsevier B.V.


Sarkar S.,Poornaprajna Institute of Scientific Research
Physica B: Condensed Matter | Year: 2014

The atoms trapped in microcavities and interacting through the exchange of virtual photons can be modeled as an anisotropic Heisenberg spin-1/2 lattice. We study the dynamics of the geometric phase of this system under the linear quenching process of laser field detuning, which shows XX criticality of the geometric phase and also gives the result of quantum criticality for different quenching rates. © 2014 Published by Elsevier B.V.


Sarkar S.,Poornaprajna Institute of Scientific Research
Advances in Theoretical and Mathematical Physics | Year: 2014

We study the quantum phase transition of light of a system when atom trapped in microcavities and interacting through the exchange of virtual photons. We predict the quantum phase transition between the photonic Coulomb blocked induce insulating phase and anisotropic exchange induced photonic superfluid phase in the system due to the existence of two Rabi frequency oscillations. The renormalization group equation shows explicitly that for this system there is no self-duality. The system also shows two Berezinskii-Kosterlitz-Thouless (BKT) transitions for the different physical situation of the system. The presence of single Rabi frequency oscillation in the system leads to the BKT transition where system shows the quantum phase transition from photonic metallic state to the Coulomb blocked induced insulating phase. For the other BKT transition when the z-component of exchange interaction is absent, the system shows the transition from the photonic metallic state to the photonic superfluid phase. We also predict the commensurate to incommensurate transition under the laser field detuning. © 2014 International Press.


Sarkar S.,PoornaPrajna Institute of Scientific Research
Physica B: Condensed Matter | Year: 2013

We study the entanglement of a two-qubit system in a superconducting quantum dot (SQD) lattice in the presence of magnetic flux and gate voltage. The ground state is always in a maximally entangled Bell state for homogeneous gate voltage. In the presence of inhomogeneous gate voltage, the half-integer magnetic flux quantum, completely washes out the entanglement of the system at zero temperature. The entanglement is much higher for the Mott insulating phase. At finite temperature, collapse of entanglement occurs for wider region of magnetic flux. © 2013 Elsevier B.V. All rights reserved.


Aravinda S.,Poornaprajna Institute of Scientific Research | Srikanth R.,Poornaprajna Institute of Scientific Research
International Journal of Theoretical Physics | Year: 2015

Nonclassical properties of correlations– like unpredictability, no-cloning and uncertainty– are known to follow from two assumptions: nonlocality and no-signaling. For two-input-two-output correlations, we derive these properties from a single, unified assumption: namely, the excess of the communication cost over the signaling in the correlation. This is relevant to quantum temporal correlations, resources to simulate quantum correlations and extensions of quantum mechanics. We generalize in the context of such correlations the nonclassicality result for nonlocal-nonsignaling correlations (Masanes et al., Phys. Rev. A 73, 012112 (2006)) and the uncertainty bound on nonlocality (Oppenheim and Wehner, Science 330(6007), 1072 (2010)), when the no-signaling condition is relaxed. © 2015, Springer Science+Business Media New York.

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