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The measurement problem concerns an apparent conflict between the two fundamental principles of quantum mechanics, namely the Schrodinger equation and the measurement postulate. These principles describe inconsistent behavior for quantum systems in so-called "measurement contexts." Many theorists have thought that the measurement problem can only be resolved by proposing a mechanistic explanation of (genuine or apparent) wavefunction collapse that avoids explicit reference to "measurement." However, I argue here that the measurement problem dissolves if we accept Humeanism about laws of nature. On a Humean metaphysics, there is no conflict between the two principles, nor is there any inherent problem with the concept of "measurement" figuring into the account of collapse.

Conjugated aromatic macrocycles are attractive due to their unique photophysical and optoelectronic properties. In particular, the cyclic radially oriented π-system of cycloparaphenylenes (CPPs) gives rise to photophysical properties unlike any other small molecule or carbon nanomaterial. CPPs have tunable emission, possess large extinction coefficients, wide effective Stokes shifts, and high quantum yields. However, accessing bright CPPs with emissions beyond 500 nm remains difficult. Herein, we present a novel and bright orange-emitting CPP-based fluorophore showing a dramatic 105 nm red-shift in emission and striking 237 nm effective Stokes shift while retaining a large quantum yield of 0.59. We postulate, and experimentally and theoretically support, that the quantum yield remains large due to the lack of intramolecular charge transfer.

Purpose To capture the multiquantum coherence (MQC) 23 Na signal. Different phase-cycling options and sequences are compared in a unified theoretical layout, and a novel sequence is developed. Methods An open source simulation overview is provided with graphical explanations to facilitate MQC understanding and access to techniques. Biases such as B0 inhomogeneity and stimulated echo signal were simulated for 4 different phase-cycling options previously described. Considerations for efficiency and accuracy lead to the implementation of a 2D Cartesian single and triple quantum imaging of sodium (CRISTINA) sequence employing two 6-step cycles in combination with a multi-echo readout. CRISTINA was compared to simultaneous single-quantum and triple-quantum-filtered MRI of sodium (SISTINA) under strong static magnetic gradient. CRISTINA capabilities were assessed on 8 × 60 mL, 0% to 5% agarose phantom with 50 to 154 mM 23 Na concentration at 7 T. CRISTINA was demonstrated subsequently in vivo in the brain. Results Simulation of B0 inhomogeneity showed severe signal dropout, which can lead to erroneous MQC measurement. Stimulated echo signal was highest at the time of triple-quantum coherences signal maximum. However, stimulated echo signal is separated by Fourier Transform as an offset and did not interfere with MQC signals. The multi-echo readout enabled capturing both single-quantum coherences and triple-quantum coherences signal evolution at once. Signal combination of 2 phase-cycles with a corresponding B0 map was found to recover the signal optimally. Experimental results confirm and complement the simulations. Conclusion Considerations for efficient MQC measurements, most importantly avoiding B0 signal loss, led to the design of CRISTINA. CRISTINA captures triple-quantum coherences and single-quantum coherences signal evolution to provide complete sodium signal characterization including T 2 ∗ fast, T 2 ∗ slow, MQC amplitudes, and sodium concentration.

Made available in DSpace on 2020-12-10T20:13:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-06 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Ba3MgNb2O9 is a double perovskite niobate with a trigonal structure with space group D-3d(3). Such a niobium-based compound has a great potential for applications as microwave dielectrics in the telecommunication industry. In this work, we report the lattice dynamics calculation results using a Short-Range Force Field Model and Density Functional Theory to represent the optical phonon modes at Gamma-point of the Brillouin zone. The classical method uses the nearest neighbor interactions through the interatomic force constants to describe the local order for Raman and infrared spectra. At the same time, density functional theory methods took into account two functionals (PBE and B3LYP) in order to provide the optical modes through second derivatives of the total energy. In both methods, theoretical optical modes are in good agreement with reported experimental data. The combination of both classical and quantum theoretical methods provided basis for a systematic discussion on the origin of the optical modes including the prediction of the dielectric tensor. We believe that this work presents useful information about the structural and vibrational characterization of Ba3MgNb2O9 perovskite and possible targeting for its application as microwave dielectrics for the communication technology. Univ Fed Amazonas, Inst Ciencias Exatas, Programa Posgrad Quim, Manaus, Amazonas, Brazil Sao Paulo State Univ, Modeling & Mol Simulat, Bauru, SP, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, Sao Carlos, Brazil CSIC, Inst Ciencia Mat Madrid, Madrid, Spain Sao Paulo State Univ, Modeling & Mol Simulat, Bauru, SP, Brazil CNPq: 432242/2018-0 CAPES: 88881.171031/2018-01 FAPESP: 2013/07296-2 FAPESP: 2019/08928-9

We report extremely strong chirality transfer from a chiral nickel complex to solvent molecules detected as Raman optical activity (ROA). Electronic energies of the complex were in resonance with the excitation-laser light. The phenomenon was observed for a wide range of achiral and chiral solvents. For chiral 2-butanol, the induced ROA was even stronger than the natural one. The observations were related to so-called quantum (molecular) plasmons that enable a strong chiral Rayleigh scattering of the resonating complex. According to a model presented here, the maximal induced ROA intensity occurs at a certain distance from the solute, in a three-dimensional "ring of fire", even after rotational averaging. Most experimental ROA signs and relative intensities could be reproduced. The effect might significantly increase the potential of ROA spectroscopy in bioimaging and sensitive detection of chiral molecules.

As a new class of sustainable carbon material, "carbon dots" is an umbrella term covering many types of materials. Herein, a broad range of techniques was used to develop the understanding of hydrothermally synthesized carbon dots, and it is shown how fine-tuning the structural features by simple reduction/oxidation reactions can drastically affect their excited-state properties. Structural and spectroscopic studies found that photoluminescence originates from direct excitation of localized fluorophores involving oxygen functional groups, whereas excitation at graphene-like features leads to ultrafast phonon-assisted relaxation and largely quenches the fluorescent quantum yields. This is arguably the first study to identify the dynamics of photoluminescence including Stokes shift and allow the relaxation pathways in these carbon dots to be fully resolved. This comprehensive investigation sheds light on how understanding the excited-state relaxation processes in different carbon structures is crucial for tuning the optical properties for any potential commercial applications.

International audience; The single-molecule magnet (SMM) properties of a series of ferrocenium complexes, [Fe(h5-C5R5)2]+ (R=Me, Bn), are reported. In the presence of an applied dc field, the slow dynamics of the magnetization in [Fe(h5-C5Me5)2]BArF are revealed. Multireference quantum mechanical calculationsshow a large energy difference between the ground and first excited states, excluding the commonly invoked, thermally activated (Orbach-like) mechanism of relaxation. In contrast, a detailed analysis of the relaxation time highlights that both direct and Raman processes are responsible forthe SMM properties. Similarly, the bulky ferrocenium complexes, [Fe(h5-C5Bn5)2]BF4 and [Fe(h5-C5Bn5)2]PF6, also exhibit magnetization slow dynamics, however an additional relaxation process is clearly detected for these analogous systems.

We show that the mutual, through‐space compression of atomic volume experienced by approaching topological atoms causes an exponential increase in the intra‐atomic energy of those atoms, regardless of approach orientation. This insight was obtained using the modern energy partitioning method called interacting quantum atoms (IQA). This behaviour is consistent for all atoms except hydrogen, which can behave differently depending on its environment. Whilst all atoms experience charge transfer when they interact, the intra‐atomic energy of the hydrogen atom is more vulnerable to these changes than larger atoms. The difference in behaviour is found to be due to hydrogen's lack of a core of electrons, which, in heavier atoms, consistently provide repulsion when compressed. As such, hydrogen atoms do not always provide steric hindrance. In accounting for hydrogen's unusual behaviour and demonstrating the exponential character of the intra‐atomic energy in all other atoms, we provide evidence for IQA's intra‐atomic energy as a quantitative description of steric energy.

In this work an approach to investigate the properties of strongly localized vibrational modes of functional groups in bulk material and on solid‐state surfaces is presented. The associated normal mode vectors are approximated solely on the basis of structural information and obtained via diagonalization of a reduced Hessian. The grid‐based Numerov procedure in one and two dimensions is then applied to an adequate scan of the respective potential surface yielding the associated vibrational wave functions and energy eigenvalues. This not only provides a detailed description of anharmonic effects but also an accurate inclusion of the coupling between the investigated vibrational states on a quantum mechanical level. All results obtained for the constructed normal modes are benchmarked against their analytical counterparts obtained from the diagonalization of the total Hessian of the entire system. Three increasingly complex systems treated at quantum chemical level of theory have been considered, namely the symmetric and asymmetric stretch vibrations of an isolated water molecule, hydroxyl groups bound to the surface of GeO2 (001), α‐quartz(001) and Rutil (001) as well as crystalline Li2NH serving as an example for a bulk material. While the data obtained for the individual systems verify the applicability of the proposed methodology, comparison to experimental data demonstrates the accuracy of this methodology despite the restriction to limit this methodology to a few selected vibrational modes. The possibility to investigate vibrational phenomena of localized normal modes without the requirement of executing costly harmonic frequency calculations of the entire system enables the application of this method to cases in which the determination of normal modes is prohibitively expensive or not available for a particular level of theory. © 2018 Wiley Periodicals, Inc.

The Relativistic And Quantum Electronic Theory (RAQET) program is a new software package, which is designed for large‐scale two‐component relativistic quantum chemical (QC) calculations. The package includes several efficient schemes and algorithms for calculations involving large molecules which contain heavy elements in accurate relativistic formalisms. These calculations can be carried out in terms of the two‐component relativistic Hamiltonian, wavefunction theory, density functional theory, core potential scheme, and evaluation of electron repulsion integrals. Furthermore, several techniques, which have frequently been used in non‐relativistic QC calculations, have been customized for relativistic calculations. This article introduces the brief theories and capabilities of RAQET with several calculation examples. © 2018 The Authors Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

11 págs., 9 figs., tab., Clathrate hydrates of CO2 have been proposed as potential molecular materials in tackling important environmental problems related to greenhouse gases capture and storage. Despite the increasing interest in such hydrates and their technological applications, a molecular‐level understanding of their formation and properties is still far from complete. Modeling interactions is a challenging and computationally demanding task, essential to reliably determine molecular properties. First‐principles calculations for the CO2 guest in all sI, sII, and sH clathrate cages were performed, and the nature of the guest–host interactions, dominated by both hydrogen‐bond and van der Waals forces, was systematically investigated. Different families of density functionals, as well as pairwise CO2@H2O model potentials versus wavefunction‐based quantum approaches were studied for CO2 clathrate‐like systems. Benchmark energies for new distance‐dependent datasets, consisting of potential energy curves sampling representative configurations of the systems at the repulsive, near‐equilibrium, and asymptotic/long‐range regions of the full‐dimensional surface, were generated, and a general protocol was proposed to assess the accuracy of such conventional and modern approaches at minimum and non‐minimum orientations. Our results show that dispersion interactions are important in the guest–host stabilization energies of such clathrate cages, and the encapsulation of the CO2 into guest‐free clathrate cages is always energetically favorable. In addition, the orientation of CO2 inside each cage was explored, and the ability of current promising approaches to accurately describe non‐covalent CO2@H2O guest–host interactions in sI, sII, and sH clathrates was discussed, providing information for their applicability to future multiscale computer simulations., MINECO (Spain). Grant Number: FIS2014-51933-P, FIS2017-83157-P CSIC (Spain). Grant Number: ICOOPB20214

Quantum-rotor-induced polarization is closely related to para-hydrogen-induced polarization. In both cases the hyperpolarized spin order derives from rotational interaction, and the Pauli principle by which the symmetry of the rotational ground state dictates the symmetry of the associated nuclear spin state. In quantum-rotor-induced polarization there may be several spin states associated with the rotational ground state, and the hyperpolarization is typically generated by hetero-nuclear cross-relaxation. This review discusses preconditions for quantum-rotor-induced polarization for both the 1-dimensional methyl rotor and the asymmetric rotor H 2 17 O@C 60 , i.e. a single water molecule encapsulated in fullerene C 60 . Experimental results are presented for both rotors.

Generalizing our recent work on relativistic generalizations of the quantum theory of atoms in molecules, we present the general setting under which the principle of stationary action for a region leads to open quantum subsystems. The approach presented here is general and works for any Hamiltonian, and when a reasonable Lagrangian is selected, it often leads to the integral of the Laplacian of the electron density on the region vanishing as a necessary condition for the zero-flux surface. Alternatively, with this method, one can design a Lagrangian that leads to a surface of interest (though this Lagrangian may not be, and indeed probably will not be, "reasonable"). For any reasonable Lagrangian for the electronic wave function and any two-component method (related by integration by parts to the Hamiltonian) considered, the Bader definition of an atom is recaptured. © 2018 Wiley Periodicals, Inc.

Optimisation problems exist widely in real-life applications. A quantum-inspired optimisation algorithm under the harmonic oscillator well transforms the function optimisation into solving the ground state wave function through the transformation of the Schrodinger equation. A novel approach using energy equipartition for the exchange of energy information is present to construct the candidate solutions. Elitists preservation is utilised to preserve dominant energy information for the improvement of search efficiency. Experiments on benchmark test functions for the 30D problem show that the proposed approaches are more effective than compared algorithms.

Atoms deposited on two-dimensional (2D) electronic materials, such as graphene, can exhibit unconventional many-body correlations, not accessible in other settings. All of these are driven by van der Waals forces: between the atoms themselves and atom-material interactions. For example $^4$He atoms on 2D materials can potentially form a variety of exotic quantum states of matter, such as two-dimensional supersolids and superfluids, in addition to solid phases. For the "most quantum" case of a single helium layer we discuss, from a theoretical perspective, how the effective low-energy (Bose-Hubbard) description can take advantage of the extreme sensitivity of this unique system to the interplay between the atomic (helium) and solid-state (graphene) components. Due to the extraordinary variety and tunability of 2D electronic materials, we envisage that a wide range of correlated atomic phases can be realized under favorable conditions. We also outline exciting possibilities in the opposite extreme of many atomic layers forming a liquid on top of graphene -- in this case a so-called "spinodal de-wetting" pattern can form at the liquid-vapor interface which reflects the presence and electronic properties of graphene underneath. Such patterns could be manipulated by choosing different atoms and materials, with potential technological applications., Comment: 10 pages, 9 figures

We introduce EXcitonic Analysis Tool (EXAT), a program able to compute optical spectra of large excitonic systems directly from the output of quantum mechanical calculations performed with the popular Gaussian 16 package. The software is able to combine in an excitonic scheme the single-chromophore properties and exciton couplings to simulate energies, coefficients, and excitonic spectra (UV-vis, CD, and LD). The effect of the environment can also be included using a Polarizable Continuum Model. EXAT also presents a simple graphical user interface, which shows on-screen both site and exciton properties. To show the potential of the method, we report two applications on a a chiral perturbed BODIPY system and DNA G-quadruplexes, respectively. The program is available online at http://molecolab.dcci.unipi.it/tools/. © 2017 Wiley Periodicals, Inc.

Lead halide perovskite quantum dots (QDs) have shown great potential for optoelectronic and quantum photonic applications. Although controversy remains about the electronic fine structures of bulk perovskites due to the strong spin-orbit coupling affecting the conduction bands, compelling evidence indicates that the ground states of perovskite QDs remain dark, limiting their applications in optoelectronic devices. Here, it is demonstrated that photoexcitation can induce large intrinsic magnetic fields in Mn-doped CsPbBr3 perovskite QDs. Equivalent to applying an external magnetic field, the light-induced field causes giant Zeeman splitting to the bright triplet states and brightens the dark singlet ground state, thus effectively rendering a partially bright ground state in the doped QDs. These findings here may contribute to the understanding of the electronic fine structures in perovskite QDs and demonstrate a potential approach for creating semiconductor nanostructures that can serve as bright light sources.

Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition‐metal dichalcogenides (TMDs) and few‐layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic‐dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra‐narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many‐body correlations and other state‐of‐the‐art technologies. This timely demonstration paves the way for further exploration of ultralow‐threshold quantum‐emitting devices with unmatched design freedom and spectral tunability.

Controlling magnetic states by a small current is essential for the next-generation of energy-efficient spintronic devices. However, it invariably requires considerable energy to change a magnetic ground state of intrinsically quantum nature governed by fundamental Hamiltonian, once stabilized below a phase transition temperature. We report that surprisingly an in-plane current can tune the magnetic state of nm-thin van der Waals ferromagnet Fe3GeTe2 from a hard magnetic state to a soft magnetic state. It is the direct demonstration of the current-induced substantial reduction of the coercive field. This surprising finding is possible because the in-plane current produces a highly unusual type of gigantic spin-orbit torque for Fe3GeTe2. And we further demonstrate a working model of a new nonvolatile magnetic memory based on the principle of our discovery in Fe3GeTe2, controlled by a tiny current. Our findings open up a new window of exciting opportunities for magnetic van der Waals materials with potentially huge impacts on the future development of spintronic and magnetic memory., 61 pages, 4 main figures, 14 supporting figures

A quantum-classical transition equation in complex space is derived in the framework of the complex quantum Hamilton–Jacobi formalism. The transition equation is obtained by subtracting a complex-valued quantum potential term from the complex-extended time-dependent Schrodinger equation (TDSE). It is shown that the nonlinear transition equation is equivalent to a linear scaled TDSE with a rescaled Planck's constant. Employing the quantum momentum function defined by the gradient of the complex action, we can analyze the quantum-classical transition of physical systems using complex transition trajectories. Complex transition trajectories are presented for the free Gaussian wave packet, the harmonic oscillator, and the Morse potential. This study demonstrates that the transition equation provides a continuous description for the quantum-classical transition of physical systems in complex space.

authoren Time-periodic perturbations due to classical electromagnetic fields are useful to engineer the topological properties of matter using the Floquet theory. Here, we investigate the effect of quantized electromagnetic fields by focusing on the quantized light–matter interaction on the edge state of a quantum spin Hall insulator. We show that this interaction can be studied using an inhomogeneous Dicke model and that the corresponding Hamiltonian is integrable. A Dicke-type superradiant phase transition occurs at arbitrary weak coupling and the electronic spectrum acquires a finite gap. In addition, when the total number of excitations are fixed, a photocurrent is generated along the edge, pseudoquantized as in the low-frequency limit and decaying as for high frequencies with being the photon frequency.

Raman spectra of orthoenstatite have been computed from first principles, employing the hybrid Hamiltonian WC1LYP.[1] The calculated data show excellent agreement with the experimental data from literature with an absolute average difference of ~5 cm−1. The quantum mechanical simulation allowed the assignment of Raman features to specific vibrational modes. This enabled to assess quantitatively the contributions of internal (tetrahedral stretching) and external (tetrahedral chains and M1 and M2 cations) vibrations. Moreover, the mass substitution of 56Fe for 24Mg in the M1 and M2 sites and of 30Si and 18O for the 28Si and 16O sites, pointed out the relative contributions of the cations to each mode within different sites. The description of the Raman modes enabled to relate the major experimental peaks to specific structural vibrations, and to link the changes in crystal structure to those modes with pressure, temperature and composition. The results provide new clues to identify most suitable peaks for the investigation of the intracrystalline ordering of Fe and Mg in the M1 and M2 sites, and of Al in the tetrahedral and octahedral sites. Moreover we have been able to identify those peaks which are related to structural features, like tetrahedral bond distances. Copyright © 2016 John Wiley & Sons, Ltd.

The Pauli exclusion principle requires that spin orbitals have occupations between zero and one. For pure quantum systems, however, the occupations of the spin orbitals are constrained by additional inequalities known as the generalized Pauli constraints. If the occupation numbers saturate (or nearly saturate) the generalized Pauli constraints, then the occupation numbers are said to be pinned (or quasi-pinned) to the constraints. Here, we assess the complexity of electron correlation of excited states from the pinning or quasi-pinning of the occupation numbers to the generalized Pauli constraints where the degree of pinning encodes information about the structure of the wave function including correlation and entanglement. Results are presented for three- and four-electron atoms and molecules, the five-electron cyclopentadienyl radical, and the seven-electron Fenna-Matthews-Olson complex in green-sulfur bacteria. The data shows that even when the ground-state occupation numbers are pinned, the occupation numbers of excited states manifest pinned, quasi-pinned, and unpinned behavior, reflecting the complexity of electron correlation and entanglement in excited states. © 2016 Wiley Periodicals, Inc.

We developed a unique integrated software package (called Electron Tunneling in Proteins Program or ETP) which provides an environment with different capabilities such as tunneling current calculation, semi-empirical quantum mechanical calculation, and molecular modeling simulation for calculation and analysis of electron transfer reactions in proteins. ETP program is developed as a cross-platform client-server program in which all the different calculations are conducted at the server side while only the client terminal displays the resulting calculation outputs in the different supported representations. ETP program is integrated with a set of well-known computational software packages including Gaussian, BALLVIEW, Dowser, pKip, and APBS. In addition, ETP program supports various visualization methods for the tunneling calculation results that assist in a more comprehensive understanding of the tunneling process. © 2016 Wiley Periodicals, Inc.

This paper illustrates various aspects of the ER=EPR conjecture. It begins with a brief heuristic argument, using the Ryu-Takayanagi correspondence, for why entanglement between black holes implies the existence of Einstein-Rosen bridges. The main part of the paper addresses a fundamental question: Is ER=EPR consistent with the standard postulates of quantum mechanics? Naively it seems to lead to an inconsistency between observations made on entangled systems by different observers. The resolution of the paradox lies in the properties of multiple black holes, entangled in the Greenberger-Horne-Zeilinger pattern. The last part of the paper is about entanglement as a resource for quantum communication. ER=EPR provides a way to visualize protocols like quantum teleportation. In some sense teleportation takes place through the wormhole, but as usual, classical communication is necessary to complete the protocol.

This work presents a quantum mechanical simulation of an indium gallium nitride (InGaN) based light-emitting diode (LED) using the non-equilibrium Green's function (NEGF) method. Due to the wurtzite crystal structure, such LEDs exhibit strong polarization-induced electric fields at heterointerfaces. Standard simulation methods based on the drift-diffusion (DD) model do not take into account potentially important transport mechanisms such as quantum mechanical tunneling or non-equilibrium carrier distributions in the device. These effects are included in the NEGF model, while the semi-classical models employ parametrized approximations. In principle, the NEGF simulation therefore allows a more realistic view of the physical process that take place in the LEDs.

We discuss analytically the stationary viscous quantum hydrodynamic model including a barrier potential, which is a nonlinear system of partial differential equations of mixed order in the sense of Douglis–Nirenberg. Combining a reformulation by means of an adjusted Fermi level, a variational functional, and a fixed point problem, we prove the existence of a weak solution. There are no assumptions on the size of the given data or their variation. We also provide various estimates of the solution that are independent of the quantum parameters. Copyright © 2015 John Wiley & Sons, Ltd.

We extend the method of Silvestrelli [P. L. Silvestrelli, J. Chem. Phys. 139, 054106 (2013)] to approximate long-range van der Waals interactions at the density functional level of theory to periodic systems. The eventual approach is based on a combination of maximally localized Wannier functions with the quantum harmonic oscillator-model. Applying this scheme to study London dispersion forces between graphene and water layers, we find that collective many-body effects beyond simple pair-wise additive interactions are essential to accurately describe van der Waals forces.

We present in this work the calculation of Bohmian quantum trajectories representing the wave function propagation in a crystal for a focused electron probe in a scanning transmission electron microscope (STEM). The wave function and quantum trajectories are obtained from the calculation of time-dependent Schrodinger equation by fast Fourier transformation multislice algorithm. In our work, the Bohmian quantum trajectories of a scanning probe penetrating a Cu crystal are studied as an example of this calculation scheme. The results help us to better understand the electron diffraction process in a microscopic imaging from a trajectory-based point of view. This Bohmian quantum trajectory method can be used to extend the application of classical Monte Carlo method from the study of electron interaction with amorphous solid to crystalline structure.

Information entropic measures such as Fisher information, Shannon entropy, Onicescu energy and Onicescu Shannon entropy of a symmetric double-well potential are calculated in both position and momentum space. Eigenvalues and eigenvectors of this system are obtained through a variation-induced exact diagonalization procedure. The information entropy-based uncertainty relation is shown to be a better measure than conventional uncertainty product in interpreting purely quantum mechanical phenomena, such as, tunneling and quantum confinement in this case. Additionally, the phase-space description provides a semiclassical explanation for this feature. Total information entropy and phase-space area show similar behavior with increasing barrier height.

A rigorous methodology that combines a fully quantum mechanical treatment of a small system with a classical trajectory description of a large number of degrees of freedom is discussed in connection with the mechanism of decoherence. The need for mean field approximations in traditional quantum-classical calculations is removed by abandoning the delocalized wavefunction description of the quantum particle in favor of Feynman's formulation, which is based on local paths. The effects of the environment enter the quantum-classical path integral (QCPI) expression in terms of phase factors along classical trajectories, whose number grows exponentially with the number of time steps. It is argued that memory loss allows termination of trajectory branching and that the main contribution to decoherence arises from a single classical trajectory (from each sampled initial condition). Exploiting these ideas allows a dramatic reduction in the required number of trajectories, making QCPI calculations feasible. © 2015 Wiley Periodicals, Inc.

We consider extensions of certain states. The states are defined on the systems of sets that are closed under the formation of the symmetric difference (concrete quantum logics). These systems can be viewed as certain set-representable quantum logics enriched with the symmetric difference. We first show how the compactness argument allows us to extend states on Boolean algebras over such systems of sets. We then observe that the extensions are sometimes possible even for non-Boolean situations. On the other hand, a difference-closed system can be constructed such that even two-valued states do not allow for extensions. Finally, we consider these questions in a σ-complete setup and find a large class of such systems with rather interesting state properties.

Vibrational relaxation is a key issue in chemical reaction dynamics in condensed phase and at the gas-surface interface, where the environment is typically highly structured and cannot be expressed in terms of a simple friction coefficient. Rather, full knowledge of the coupling of the molecular oscillator to the environment is required, as typically subsumed in the spectral density of the environmental coupling. Here, we focus on harmonic Brownian motion and investigate the effectiveness of classical, canonical position autocorrelation functions to compute the spectral density of the coupling needed to describe vibrational relaxation in complex environments. Classical dynamics is performed on model systems, and several effects are investigated in detail, notably the presence of anharmonicity, the role of a high-frequency �Debye� cutoff in the environment and the influence of the detailed structure of the latter. The spectral densities are then used in standard independent oscillator Hamiltonian models which are numerically solved at T = 0 K to investigate quantum relaxation and decoherence

The quantum efficiency in the transfer of an initial excitation in disordered finite networks, modeled by the $k$-body embedded Gaussian ensembles of random matrices, is studied for bosons and fermions. The influence of the presence or absence of time-reversal symmetry and centrosymmetry/centrohermiticity are addressed. For bosons and fermions, the best efficiencies of the realizations of the ensemble are dramatically enhanced when centrosymmetry (centrohermiticity) is imposed. For few bosons distributed in two single-particle levels this permits perfect state transfer for almost all realizations when one-particle interactions are considered. For fermionic systems the enhancement is found to be maximal for cases when all but one single particle levels are occupied.

Few statistics other than the named three have opened the path to understanding of so many natural laws and formulas employed in the engineering practice. Engineers interested in origins of expressions they may be using in their work will find some of them in this paper. Planck's Radiation and Stefan–Boltzmann Laws, Maxwell's Velocity Distributions, P-N diode equation, and intrinsic hole and electron concentrations in semiconductors are some examples. No new inventions are presented and the topics addressed are treated in books on statistical mechanics, thermodynamics, quantum and classical physics, chemistry and others. The contribution is an integration of a broad range of sciences underlying the formulas of interest under one roof of a relatively short paper. All derivations are done at the engineering level and originate in the first principles of conservation and quantization. Discrete mathematics is employed throughout and provides direct access to computerized experimentation. The appendixes assist the uninitiated in quantum physics and provide an ample collection of useful supporting material. © 2015 Wiley Periodicals, Inc. Comput. Appl. Eng. Educ. Comput Appl Eng Educ 23:746–759, 2015; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21647

In a previous study, we investigate the bound states of the Hamiltonian describing a quantum particle living on three dimensional straight strip of width d. We impose the Neumann boundary condition on a disk window of radius a and Dirichlet boundary conditions on the remained part of the boundary of the strip. We proved that such system exhibits discrete eigenvalues below the essential spectrum for any a > 0. In the present work, we study the effect of the presence of a magnetic field of Aharonov–Bohm type on this system. Precisely, we prove that in the presence of such field, there is some critical values of a0>0, for which we have absence of the discrete spectrum for . We give a sufficient condition for the existence of discrete eigenvalues. Copyright © 2015 John Wiley & Sons, Ltd.

Metalloenzymes represent a particular challenge for any rational (re)design approach because the modeling of reaction events at their metallic cofactors requires time-consuming quantum mechanical calculations, which cannot easily be reconciled with the fast, knowledge-based approaches commonly applied in protein design studies. Here, an approach for the exploration of sequence-reactivity relationships in metalloenzymes is presented (MetREx) that consists of force field-based screening of mutants that lie energetically between a wild-type sequence and the global minimum energy conformation and which should, therefore, be compatible with a given protein fold. Mutant candidates are subsequently evaluated with a fast and approximate quantum mechanical/molecular mechanical-like procedure that models the influence of the protein environment on the active site by taking partial charges and van der Waals repulsions into account. The feasibility of the procedure is demonstrated for the active site of [FeFe] hydrogenase from Desulfovibrio desulfuricans. The method described allows for the identification of mutants with altered properties, such as inhibitor-coordination energies, and the understanding of the robustness of enzymatic reaction steps with respect to variations in sequence space. © 2015 Wiley Periodicals, Inc.

In this paper, laser-induced field-free alignment of CO2 in mixtures with Ar is investigated under dissipative conditions (up to 15 bars) at room temperature. The degree of alignment is temporally monitored by a polarization spectroscopy technique, where a weak probe pulse measures the transient birefringence resulting from the alignment. The data are analyzed with a quantum mechanical density matrix formalism using properly J-dependent and M-dependent state-to-state transfer rates, which was previously successfully tested on pure CO2 and CO2–He mixtures. The same consistency is obtained between experiments and calculations, in particular the decay times of both the transient revivals and the permanent component of the alignment are accurately predicted by the model. Copyright © 2015 John Wiley & Sons, Ltd.

Following a Four Dimensional Renormalization approach to ultraviolet divergences (FDR), we extend the concept of predictivity to non-renormalizable quantum field theories at arbitrarily large perturbative orders. The idea of topological renormalization is introduced, which keeps a finite value for the parameters of the theory by trading the usual order-by-order renormalization procedure for an order-by-order redefinition of the perturbative vacuum. One additional measurement is then sufficient to systematically compute quantum corrections at any loop order, with no need of absorbing ultraviolet infinities in the Lagrangian.