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Results for "Nawaf Nazir"

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Convex inner approximation of the feeder hosting capacity limits on dispatchable demandMay 14 2019This paper presents a method to obtain a convex inner approximation that aims to improve the feasibility of optimal power flow (OPF) models in distribution feeders. For a resistive distribution network, both real and reactive power effect the node voltages ... More
Photon statistics from a resonantly driven quantum dotNov 01 2007Nov 03 2008Photon correlations in the emission of a resonantly driven quantum dot are investigated, accounting for the influence of the solid-state phonon environment. An analytical expression is derived for the second-order fluorescence intensity correlation function, ... More
SPECTRWM: Spectral Random Walk Method for the Numerical Solution of Stochastic Partial Differential EquationsAug 02 2016The numerical solution of stochastic partial differential equations (SPDE) presents challenges not encountered in the simulation of PDEs or SDEs. Indeed, the roughness of the noise in conjunction with nonlinearities in the drift typically make these equations ... More
Correlation-dependent coherent to incoherent transitions in resonant energy transfer dynamicsJun 02 2009Oct 05 2009I investigate energy transfer in a donor-acceptor pair beyond weak system-bath coupling. I identify a transition from coherent to incoherent dynamics with increasing temperature, due to multi-phonon effects not captured by a standard weak-coupling treatment. ... More
On the intersection of rational transversal subtoriMar 12 2007Jan 22 2008We show that under a suitable transversality condition, the intersection of two rational subtori in an algebraic torus $(\C^*)^n$ is a finite group which can be determined using the torsion part of some associated lattice. Applications are given to the ... More
On Metropolis Integrators for Molecular DynamicsSep 19 2013This paper invites the reader to experiment with an easy-to-use MATLAB implementation of Metropolis integrators for Molecular Dynamics (MD) simulation. These integrators are analysis-based, in the sense that they can rigorously simulate dynamics along ... More
Cayley Splitting for Second-Order Langevin Stochastic Partial Differential EquationsJul 18 2017We give accurate and ergodic numerical methods for semilinear, second-order Langevin stochastic partial differential equations (SPDE). As a byproduct, we also give good geometric numerical methods for their infinite-dimensional Hamiltonian counterpart. ... More
Stochastic Variational IntegratorsAug 16 2007Oct 23 2007This paper presents a continuous and discrete Lagrangian theory for stochastic Hamiltonian systems on manifolds. The main result is to derive stochastic governing equations for such systems from a critical point of a stochastic action. Using this result ... More
Lorentz Distributed Noncommutative $F(T,T_G)$ Wormhole SolutionsFeb 02 2018The aim of this paper is to study static spherically symmetric noncommutative $F(T,T_G)$ wormhole solutions along with Lorentzian distribution. Here, $T$ and $T_G$ are torsion scalar and teleparallel equivalent Gauss-Bonnet term, respectively. We take ... More
Stochastic Variational Partitioned Runge-Kutta Integrators for Constrained SystemsSep 14 2007Sep 23 2007Stochastic variational integrators for constrained, stochastic mechanical systems are developed in this paper. The main results of the paper are twofold: an equivalence is established between a stochastic Hamilton-Pontryagin (HP) principle in generalized ... More
Common Fixed Points of Weakly Commuting Multivalued Mappings on Domain of Sets Endowed with Directed GraphMay 31 2016In this paper, the existence of coincidence points and common fixed points for multivalued mappings satisfying certain graphic {\psi}-contraction contractive conditions with set-valued domain endowed with a graph, without appealing to continuity, is established. ... More
Energy-Momentum Problem of Bell-Szekeres Metric in General Relativity and Teleparallel GravityJan 12 2008This paper is devoted to the investigation of the energy-momentum problem in two theories, i.e., General Relativity and teleparallel gravity. We use Einstein, Landau-Lifshitz, Bergmann-Thomson and M\"{o}ller's prescriptions to evaluate energy-momentum ... More
The $f$- and $h$-vectors of Interval SubdivisionsJun 11 2018The interval subdivision $\Int(\Delta)$ of a simplicial complex $\Delta$ was introduced by Walker. We give the complete combinatorial description of the entries of the transformation matrices from the $f$- and $h$-vectors of $\Delta$ to the $f$- and $h$-vectors ... More
Ballistic Transport at Uniform TemperatureOct 08 2007Oct 17 2007A paradigm for isothermal, mechanical rectification of stochastic fluctuations is introduced in this paper. The central idea is to transform energy injected by random perturbations into rigid-body rotational kinetic energy. The prototype considered in ... More
Ergodicity of Langevin Processes with Degenerate Diffusion in MomentumsOct 23 2007Apr 10 2008This paper introduces a geometric method for proving ergodicity of degenerate noise driven stochastic processes. The driving noise is assumed to be an arbitrary Levy process with non-degenerate diffusion component (but that may be applied to a single ... More
Common Fixed Point Results for Family of Generalized Multivalued F-contraction Mappings in Ordered Metric SpacesMay 31 2016In this paper, we study the existence of common fixed points of family of multivalued mappings satisfying generalized F-contractive conditions in ordered metric spaces. These results establish some of the general common fixed point theorems for family ... More
Electron Counting Statistics for Non-Additive EnvironmentsMar 12 2019Molecular electronics is a rapidly developing field focused on using molecules as the structural basis for electronic components. It is common in such devices for the system of interest to couple simultaneously to multiple environments. Here we consider ... More
On $\g$- and local $\g$-Vectors of the Interval SubdivisionJul 08 2018We show that the $\g$-vector of the interval subdivision of a simplicial complex with a nonnegative and symmetric $h$-vector is nonnegative. In particular, we prove that such $\g$-vector is the $f$-vector of some balanced simplicial complex. Moreover, ... More
The reaction coordinate mapping in quantum thermodynamicsMay 21 2018We present an overview of the reaction coordinate approach to handling strong system-reservoir interactions in quantum thermodynamics. This technique is based on incorporating a collective degree of freedom of the reservoir (the reaction coordinate) into ... More
Gauge ambiguities imply Jaynes-Cummings physics remains valid in ultrastrong coupling QEDMay 16 2018Jan 30 2019Ultrastrong-coupling between two-level systems and radiation is important for both fundamental and applied quantum electrodynamics (QED). Such regimes are identified by the breakdown of the rotating-wave approximation, which applied to the quantum Rabi ... More
Ultrastrong time-dependent light-matter interactions are gauge-relativeFeb 13 2019Time-dependent Hamiltonians are a widespread means by which to describe controllable experimental operations. In particular, control over light-matter interactions is vital for numerous applications. Due to gauge-freedom, there are many different definitions ... More
Admissible local systems for a class of line arrangementsJan 23 2008Feb 22 2008A rank one local system $\LL$ on a smooth complex algebraic variety $M$ is admissible roughly speaking if the dimension of the cohomology groups $H^m(M,\LL)$ can be computed directly from the cohomology algebra $H^*(M,\C)$. We say that a line arrangement ... More
Geometric integrators and the Hamiltonian Monte Carlo methodNov 14 2017This paper surveys in detail the relations between numerical integration and the Hamiltonian (or hybrid) Monte Carlo method (HMC). Since the computational cost of HMC mainly lies in the numerical integrations, these should be performed as efficiently ... More
Randomized Hamiltonian Monte CarloNov 30 2015Tuning the duration of the Hamiltonian flow in Hamiltonian Monte Carlo (also called Hybrid Monte Carlo) (HMC) involves a tradeoff between computational and sampling efficiency, which is typically challenging to resolve in a satisfactory way. In this article ... More
Fault-tolerance against loss for photonic FTQECMay 07 2014In general, fault-tolerant quantum error correction (FTQEC) procedures are designed to detect, correct, and be fault-tolerant against errors occurring within the qubit subspace. But in some qubit implementations, additional "leakage" errors can occur ... More
In Vivo WBAN Communication: Design and ImplementationJun 28 2018Jul 20 2018The emerging in vivo communication and networking system is a prospective component in advancing healthcare delivery and empowering the development of new applications and services. In vivo communications is based on networked cyber-physical systems of ... More
Aspects of Quantum Coherence in NanosystemsMar 16 2009Coherence is a familiar concept in physics: It is the driving force behind wavelike phenomena such as the diffraction of light. Moreover, wave-particle duality implies that all quantum objects can exhibit coherence, and this quantum coherence is crucial ... More
Separable Quadratic Stochastic OperatorsApr 23 2009We consider quadratic stochastic operators, which are separable as a product of two linear operators. Depending on properties of these linear operators we classify the set of the separable quadratic stochastic operators: first class of constant operators, ... More
Continuous-time Random Walks for the Numerical Solution of Stochastic Differential EquationsFeb 17 2015Mar 11 2015This paper introduces time-continuous numerical schemes to simulate stochastic differential equations (SDEs) arising in mathematical finance, population dynamics, chemical kinetics, epidemiology, biophysics, and polymeric fluids. These schemes are obtained ... More
A patch that imparts unconditional stability to certain explicit integrators for SDEsOct 20 2010This paper proposes a simple strategy to simulate stochastic differential equations (SDE) arising in constant temperature molecular dynamics. The main idea is to patch an explicit integrator with Metropolis accept or reject steps. The resulting `Metropolized ... More
Overcoming non-Markovian dephasing in single photon sources through post-selectionJun 06 2008Jan 21 2009We study the effects of realistic dephasing environments on a pair of solid-state single-photon sources in the context of the Hong-Ou-Mandel dip. By means of solutions for the Markovian or exact non-Markovian dephasing dynamics of the sources, we show ... More
Hamilton-Pontryagin Integrators on Lie Groups: Introduction and Structure-Preserving PropertiesJan 07 2008In this paper structure-preserving time-integrators for rigid body-type mechanical systems are derived from a discrete Hamilton-Pontryagin variational principle. From this principle one can derive a novel class of variational partitioned Runge-Kutta methods ... More
Coupling and Convergence for Hamiltonian Monte CarloMay 01 2018Based on a new coupling approach, we prove that the transition step of the Hamiltonian Monte Carlo algorithm is contractive w.r.t. a carefully designed Kantorovich (L1 Wasserstein) distance. The lower bound for the contraction rate is explicit. Global ... More
Randomized Hamiltonian Monte CarloNov 30 2015Oct 27 2016Tuning the durations of the Hamiltonian flow in Hamiltonian Monte Carlo (also called Hybrid Monte Carlo) (HMC) involves a tradeoff between computational cost and sampling quality, which is typically challenging to resolve in a satisfactory way. In this ... More
Teleparallel Energy-Momentum Distribution of Locally Rotationally Symmetric SpacetimesDec 11 2014In this paper, we explore the energy-momentum distribution of locally rotationally symmetric (LRS) spacetimes in the context of the teleparallel theory of gravity by considering the three metrics, I, II and III, representing the whole class of LRS sapcetimes. ... More
Quantum correlations of light and matter through environmental transitionsDec 18 2014Mar 31 2016One aspect of solid-state photonic devices that distinguishes them from their atomic counterparts is the unavoidable interaction between system excitations and lattice vibrations of the host material. This coupling may lead to surprising departures in ... More
Coherent and incoherent dynamics in excitonic energy transfer: correlated fluctuations and off-resonance effectsSep 20 2010Apr 04 2011We study the nature of the energy transfer process within a pair of coupled two-level systems (donor and acceptor) subject to interactions with the surrounding environment. Going beyond a standard weak-coupling approach, we derive a master equation within ... More
Environmental dynamics, correlations, and the emergence of noncanonical equilibrium states in open quantum systemsOct 31 2013Sep 25 2014Quantum systems are invariably open, evolving under surrounding influences rather than in isolation. Standard open quantum system methods eliminate all information on the environmental state to yield a tractable description of the system dynamics. By ... More
Fractals of generalized F- Hutchinson operator in b-metric spacesMay 31 2016The aim of this paper is to construct a fractal with the help of a finite family of generalized F-contraction mappings, a class of mappings more general than contraction mappings, defined in the setup of b-metric space. Consequently, we obtain a variety ... More
Electronic excitation dynamics in multichromophoric systems described via a polaron-representation master equationJun 14 2011Oct 11 2011We derive a many-site version of the non-Markovian time-convolutionless polaron master equation [S. Jang et al., J. Chem Phys. 129, 101104 (2008)] to describe electronic excitation dynamics in multichromophoric systems. By treating electronic and vibrational ... More
Metropolis Integration Schemes for Self-Adjoint DiffusionsSep 19 2013Mar 31 2014We present explicit methods for simulating diffusions whose generator is self-adjoint with respect to a known (but possibly not normalizable) density. These methods exploit this property and combine an optimized Runge-Kutta algorithm with a Metropolis-Hastings ... More
Performance of a quantum heat engine at strong reservoir couplingSep 13 2016We study a quantum heat engine at strong coupling between the system and the thermal reservoirs. Exploiting a collective coordinate mapping, we incorporate system-reservoir correlations into a consistent thermodynamic analysis, thus circumventing the ... More
On the admissibility of certain local systemNov 08 2013A rank one local system on the complement of a hyperplane arrangement is said to be admissible if it satisfies certain non-positivity condition at every resonant edges. It is known that the cohomology of admissible local system can be computed combinatorially. ... More
A Dynamical Systems Approach to Modeling and Analysis of Transactive Energy CoordinationOct 03 2018Under transactive (market-based) coordination, a population of distributed energy resources (DERs), such as thermostatically controlled loads (TCLs) and storage devices, bid into an energy market. Consequently, a certain level of demand will be cleared ... More
Creating Two-Dimensional Electron Gas in Nonpolar Oxide Interface via Polarization Discontinuity: First-Principles Analysis of CaZrO3/SrTiO3 HeterostructureAug 03 2015We studied strain-induced polarization and resulting conductivity in the nonpolar/nonpolar CaZrO3/SrTiO3 (CZO/STO) heterostructure (HS) system by means of first-principles electronic structure calculations. By modeling four types of CZO/STO HS-based slab ... More
Quantum dot Rabi rotations beyond the weak exciton-phonon coupling regimeSep 06 2010Nov 25 2010We study the excitonic dynamics of a driven quantum dot under the influence of a phonon environment, going beyond the weak exciton-phonon coupling approximation. By combining the polaron transform and time-local projection operator techniques we develop ... More
A Metrics Based Model for Understandability QuantificationApr 26 2010Software developers and maintainers need to read and understand source programs and other software artifacts. The increase in size and complexity of software drastically affects several quality attributes, especially understandability and maintainability. ... More
A Glance into the Future of Human Computer InteractionJul 20 2011Computers have a direct impact on our lives nowadays. Human's interaction with the computer has modified with the passage of time as improvement in technology occurred the better the human computer interaction became. Today we are facilitated by the operating ... More
Performance of a quantum heat engine at strong reservoir couplingSep 13 2016Mar 29 2017We study a quantum heat engine at strong coupling between the system and the thermal reservoirs. Exploiting a collective coordinate mapping, we incorporate system-reservoir correlations into a consistent thermodynamic analysis, thus circumventing the ... More
Linear Classification of data with Support Vector Machines and Generalized Support Vector MachinesMay 31 2016In this paper, we study the support vector machine and introduced the notion of generalized support vector machine for classification of data. We show that the problem of generalized support vector machine is equivalent to the problem of generalized variational ... More
Quantum State Tuning of Energy Transfer in a Correlated EnvironmentJul 29 2009Jul 15 2010We investigate multichromophoric energy transfer allowing for bath-induced fluctuations at different sites to be correlated. As a prototype system we consider a light-harvesting antenna surrounding a reaction center. We show that the interplay between ... More
A Glance into the Future of Human Computer InteractionsJul 21 2011Computers have a direct impact on our lives nowadays. Human's interaction with the computer has modified with the passage of time as improvement in technology occurred the better the human computer interaction became. Today we are facilitated by the operating ... More
An Efficient Algebraic Criterion for ShellabilityMay 26 2017Dec 14 2017In this paper, we give a new and efficient algebraic criterion for the pure as well as non-pure shellability of simplicial complex $\Delta$ over [n]. We also give an algebraic characterization of a leaf in a simplicial complex (defined in [8]). Moreover, ... More
Modelling exciton-phonon interactions in optically driven quantum dotsNov 04 2015Jun 13 2016We provide a self-contained review of master equation approaches to modelling phonon effects in optically driven self-assembled quantum dots. Coupling of the (quasi) two-level excitonic system to phonons leads to dissipation and dephasing, the rates of ... More
Consistent treatment of coherent and incoherent energy transfer dynamics using a variational master equationJul 04 2011Sep 16 2011We investigate the energy transfer dynamics in a donor-acceptor model by developing a time-local master equation technique based on a variational transformation of the underlying Hamiltonian. The variational transformation allows a minimisation of the ... More
Model of the optical emission of a driven semiconductor quantum dot: phonon-enhanced coherent scattering and off-resonant sideband narrowingAug 22 2012May 30 2013We study the crucial role played by the solid-state environment in determining the photon emission characteristics of a driven quantum dot. For resonant driving, we predict a phonon-enhancement of the coherently emitted radiation field with increasing ... More
The equivariant cohomology of weighted flag orbifoldsNov 09 2017We describe the torus-equivariant cohomology of weighted partial flag orbifolds w$ \Sigma$ of type $A$. We establish counterparts of several results known for the partial flag variety that collectively constitute what we refer to as "Schubert Calculus ... More
Non-asymptotic mixing of the MALA algorithmAug 20 2010The Metropolis-Adjusted Langevin Algorithm (MALA), originally introduced to sample exactly the invariant measure of certain stochastic differential equations (SDE) on infinitely long time intervals, can also be used to approximate pathwise the solution ... More
Decoherence of geometric phase gatesOct 02 2001We consider the effects of certain forms of decoherence applied to both adiabatic and non-adiabatic geometric phase quantum gates. For a single qubit we illustrate path-dependent sensitivity to anisotropic noise and for two qubits we quantify the loss ... More
Generalizations of Nekrasov-Okounkov IdentityNov 16 2010Jun 06 2011Nekrasov-Okounkov identity gives a product representation of the sum over partitions of a certain function of partition hook length. In this paper we give several generalizations of the Nekrasov-Okounkov identity using the cyclic symmetry of the topological ... More
Tunable and dynamic polarizability tensor for asymmetric metal-dielectric super-cylindersApr 08 2019We propose a novel type of bi-anisotropic hybrid metal-dielectric structure comprising dielectric and metallic cylindrical wedges wherein the composite super-cylinder enables advanced control of electric, magnetic and magnetoelectric resonances. We establish ... More
Critical Aspects of Modern Open Source SoftwareTechnology to Support Emerging DemandsSep 01 2011Software has gained immense importance in our everyday lifeand is handling each and every aspect of today's technologicalworld. The idea of software at initial phase was implemented bya very precise minority of individual and now it's everywherewhether ... More
Linear Residuals and Gallai-Simplicial ComplexesDec 12 2016Apr 19 2017In this paper, we give a new algebraic criterion for the {\em shellability} of (non-pure) simplicial complex $\Delta$ over $[n]$, shellable in the sense of Bj\"orner and Wachs \cite{BW}. We show that the spanning simplicial complex of doubly uni-cyclic ... More
Dissipation enhanced vibrational sensing in an olfactory molecular switchMar 25 2014Feb 11 2015Motivated by a proposed olfactory mechanism based on a vibrationally-activated molecular switch, we study electron transport within a donor-acceptor pair that is coupled to a vibrational mode and embedded in a surrounding environment. We derive a polaron ... More
Optical Schemes for Quantum Computation in Quantum Dot MoleculesJul 03 2003Nov 08 2004We give three methods for entangling quantum states in quantum dots. We do this by showing how to tailor the resonant energy (Foerster-Dexter) transfer mechanisms and the biexciton binding energy in a quantum dot molecule. We calculate the magnitude of ... More
Ground state and dynamics of the biased dissipative two-state system: Beyond variational polaron theoryJan 26 2012Jun 12 2012We propose a ground-state ansatz for the Ohmic spin-boson model that improves upon the variational treatment of Silbey and Harris for biased systems in the scaling limit. In particular, it correctly captures the smooth crossover behaviour expected for ... More
Learning Shallow Detection Cascades for Wearable Sensor-Based Mobile Health ApplicationsJul 13 2016The field of mobile health aims to leverage recent advances in wearable on-body sensing technology and smart phone computing capabilities to develop systems that can monitor health states and deliver just-in-time adaptive interventions. However, existing ... More
Energy transfer in structured and unstructured environments: master equations beyond the Born-Markov approximationsNov 16 2015Apr 04 2016We explore excitonic energy transfer dynamics in a molecular dimer system coupled to both structured and unstructured oscillator environments. By extending the reaction coordinate master equation technique developed in [J. Iles-Smith, N. Lambert, and ... More
Reactor based XPS and other in-situ studies on the Effect of Substitution of Bismuth for Indium in Defect Laden Indium Oxide Hydroxide BizIn2-zO3-x(OH)y on the Photocatalytic Hydrogenation of Carbon DioxideApr 15 2019The photocatalytic activity of nanostructured In2O3-x(OH)y for the Reverse Water Gas Shift (RWGS) Reaction CO2 + H2 -> CO + H2O can be greatly enhanced by substitution of Bi(III) for In(III) in the lattice of BizIn2-zO3-xOHy. This behavior was hypothesized ... More
On Practical Aspects of Mobile Data Offloading to Wi-Fi NetworksAug 08 2015Data traffic over cellular networks is exhibiting an ongoing exponential growth, increasing by an order of magnitude every year and has already surpassed voice traffic. This increase in data traffic demand has led to a need for solutions to enhance capacity ... More
Creating excitonic entanglement in quantum dots through the optical Stark effectJun 17 2004Nov 03 2004We show that two initially non-resonant quantum dots may be brought into resonance by the application of a single detuned laser. This allows for control of the inter-dot interactions and the generation of highly entangled excitonic states on the picosecond ... More
Tradeoff between Leakage and Dephasing Errors in the Fluxonium QubitDec 19 2012Sep 30 2013We present a tradeoff between leakage and pure dephasing errors for the fluxonium circuit. We show that in the insulating regime, i.e., when the persistent current flowing across the circuit is suppressed, the pure dephasing rate decreases exponentially ... More
Tunable and dynamic polarizability tensor for asymmetric metal-dielectric meta-cylindersApr 08 2019Apr 29 2019We propose a novel type of bi-anisotropic hybrid metal-dielectric structure comprising dielectric and metallic cylindrical wedges wherein the composite meta-cylinder enables advanced control of electric, magnetic and magnetoelectric resonances. We establish ... More
Complex exchange mechanism driven ferromagnetism in half-metallic Heusler Co$_{2}$TiGe: Evidence from critical behaviorMar 26 2019We have investigated the critical phenomenon associated with the magnetic phase transition in the half-metallic full-Heusler Co$_2$TiGe. The compound undergoes a continuous ferromagnetic to paramagnetic phase transition at the Curie temperature $T_{C}$=371.5 ... More
Sr1.5Ba0.5Zn2Fe12O22 Hexaferrites Ferromagnetic Resonance and Nonlinear Excitation for Magneto-Electric DevicesJan 14 2007Jan 17 2007A magneto electric (ME) effect was reported [1] for the insulator material of helimagnetic hexaferrite of Sr1.5Ba0.5Zn2Fe12O22. In this study we are interested in investigating this materials ferromagnetic resonance to define its internal anisotropy fields. ... More
Wearable Posture Monitoring System with Vibration FeedbackSep 29 2018Around 50 billion dollars is spent yearly on therapy for low back pain in the United States alone. Low back pain is one of the most common reasons for doctor visits. Having poor posture has been found to be a main cause of lower back pain as it impacts ... More
Nano Ferrites Microwave Complex Permeability and Permittivity Measurements by T/R Technique in WaveguideJan 14 2007Jan 17 2007There is a huge demand to accurately determine the magneto-electrical properties of particles in the nano sized regime due to the modern IC technology revolution and biomedical application science. In this paper, we present a microwave waveguide measurement ... More
Analysis of quantum coherence in bismuth-doped silicon: a system of strongly coupled spin qubitsJun 16 2010Jul 04 2012There is growing interest in bismuth-doped silicon (Si:Bi) as an alternative to the well-studied proposals for silicon based quantum information processing (QIP) using phosphorus-doped silicon (Si:P). We focus here on the implications of its anomalously ... More
Anticrossings in Foerster Coupled Quantum DotsSep 11 2003Feb 15 2005We consider two coupled generic quantum dots, each modelled by a simple potential which allows the derivation of an analytical expression for the inter-dot Foerster coupling, in the dipole-dipole approximation. We investigate the energy level behaviour ... More
High fidelity all-optical control of quantum dot spins: detailed study of the adiabatic approachAug 13 2007Apr 07 2008Confined electron spins are preferred candidates for embodying quantum information in the solid state. A popular idea is the use of optical excitation to achieve the ``best of both worlds'', i.e. marrying the long spin decoherence times with rapid gating. ... More
A multi-site variational master equation approach to dissipative energy transferDec 22 2012Jul 23 2013Unitary transformations can allow one to study open quantum systems in situations for which standard, weak-coupling type approximations are not valid. We develop here an extension of the variational (polaron) transformation approach to open system dynamics, ... More
Long-lived spin entanglement induced by a spatially correlated thermal bathJul 14 2008Sep 01 2009We investigate how two spatially separated qubits coupled to a common heat bath can be entangled by purely dissipative dynamics. We identify a dynamical time scale associated with the lifetime of the dissipatively generated entanglement and show that ... More
Stabilizing Spin Coherence Through Environmental Entanglement in Strongly Dissipative Quantum SystemsJul 22 2013Mar 20 2014The key feature of a quantum spin coupled to a harmonic bath---a model dissipative quantum system---is competition between oscillator potential energy and spin tunneling rate. We show that these opposing tendencies cause environmental entanglement through ... More
Numerical Solution of second order hyperbolic telegraph equation via new Cubic Trigonometric B-Splines ApproachOct 30 2015This paper presents a new approach and methodology to solve the second order one dimensional hyperbolic telegraph equation with Dirichlet and Neumann boundary conditions using the cubic trigonometric B-spline collocation method. The usual finite difference ... More
Selective spin coupling through a single excitonMar 30 2004Oct 12 2004We present a novel scheme for performing a conditional phase gate between two spin qubits in adjacent semiconductor quantum dots through delocalized single exciton states, formed through the inter-dot Foerster interaction. We consider two resonant quantum ... More
Cubic symmetry and magnetic frustration on the $fcc$ spin lattice in K$_2$IrCl$_6$Mar 05 2019Cubic crystal structure and regular octahedral environment of Ir$^{4+}$ render antifluorite-type K$_2$IrCl$_6$ a model material showing geometrically frustrated magnetic interactions. High-resolution synchrotron powder diffraction confirms cubic symmetry ... More
Cubic symmetry and magnetic frustration on the $fcc$ spin lattice in K$_2$IrCl$_6$Mar 05 2019Apr 29 2019Cubic crystal structure and regular octahedral environment of Ir$^{4+}$ render antifluorite-type K$_2$IrCl$_6$ a model fcc antiferromagnet with a combination of Heisenberg and Kitaev exchange interactions. High-resolution synchrotron powder diffraction ... More
Long-Run Accuracy of Variational Integrators in the Stochastic ContextDec 26 2007Jan 13 2010This paper presents a Lie-Trotter splitting for inertial Langevin equations (Geometric Langevin Algorithm) and analyzes its long-time statistical properties. The splitting is defined as a composition of a variational integrator with an Ornstein-Uhlenbeck ... More
Fundamental Limits to Coherent Scattering and Photon Coalescence from Solid-State Quantum EmittersJun 20 2016The desire to produce high-quality single photons for applications in quantum information science has lead to renewed interest in exploring solid-state emitters in the weak excitation regime. Under these conditions it is expected that photons are coherently ... More
Resonant Transfer of Excitons and Quantum ComputationSep 11 2002Jan 06 2003Resonant energy transfer mechanisms have been observed in the sensitized luminescence of solids, in quantum dots and in molecular nanostructures, and they also play a central role in light harvesting processes in photosynthetic organisms. We demonstrate ... More
Separation-dependent localization in a two-impurity spin-boson modelApr 01 2010Jul 02 2010Using a variational approach we investigate the delocalized to localized crossover in the ground state of an Ohmic two-impurity spin-boson model, describing two otherwise non-interacting spins coupled to a common bosonic environment. We show that a competition ... More
A general approach to quantum dynamics using a variational master equation: Application to phonon-damped Rabi rotations in quantum dotsMay 30 2011Sep 19 2011We develop a versatile master equation approach to describe the non-equilibrium dynamics of a two-level system in contact with a bosonic environment, which allows for the exploration of a wide range of parameter regimes within a single formalism. As an ... More
Rainbow-trapping by adiabatic tuning of intragroove plasmon couplingJun 11 2014Jul 12 2014It is shown here that rendering the width of nano-grooves into a tunable parameter presents a new means of light trapping in subwavelength gratings. Particularly, in gratings with groove-widths below 150 nm, the plasmon coupling between the perimeter ... More
Survey of Extended LEACH-Based Clustering Routing Protocols for Wireless Sensor NetworksJul 11 2012An energy efficient routing protocol is the major concern in Wireless Sensor Networks (WSNs). In this survey paper, we present energy efficient hierarchical routing protocols, developed from conventional LEACH routing protocol. Main focus of our study ... More
A generalized multi-polaron expansion for the spin-boson model: Environmental entanglement and the biased two-state systemJun 19 2014Aug 11 2014We develop a systematic variational coherent state expansion for the many-body ground state of the spin-boson model, in which a quantum two-level system is coupled to a continuum of harmonic oscillators. Energetic constraints at the heart of this technique ... More
Robust adiabatic approach to optical spin entangling in coupled quantum dotsApr 14 2008Aug 28 2008Excitonic transitions offer a possible route to ultrafast optical spin manipulation in coupled nanostructures. We perform here a detailed study of the three principal exciton-mediated decoherence channels for optically-controlled electron spin qubits ... More
Inner Approximation of Minkowski Sums: A Union-Based Approach and Applications to Aggregated Energy ResourcesOct 03 2018This paper develops and compares algorithms to compute inner approximations of the Minkowski sum of convex polytopes. As an application, the paper considers the computation of the feasibility set of aggregations of distributed energy resources (DERs), ... More
Unveiling environmental entanglement in strongly dissipative qubitsJan 30 2013The coupling of a qubit to a macroscopic reservoir plays a fundamental role in understanding the complex transition from the quantum to the classical world. Considering a harmonic environment, we use both intuitive arguments and numerical many-body quantum ... More
A counterexample showing the semi-explicit Lie-Newmark algorithm is not variationalMay 18 2010May 28 2010This paper presents a counterexample to the conjecture that the semi-explicit Lie-Newmark algorithm is variational. As a consequence the Lie-Newmark method is not well-suited for long-time simulation of rigid body-type mechanical systems. The counterexample ... More
Vibronic resonances facilitate excited state coherence in light harvesting proteins at room temperatureMar 01 2015Jul 23 2015Until recently it was believed that photosynthesis, a fundamental process for life on earth, could be fully understood with semi-classical models. However, puzzling quantum phenomena have been observed in several photosynthetic pigment-protein complexes, ... More