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Quantum computer

Mostafa Fakhraee, Mohammad Reza Gholami
The effects of ester addition on structural and dynamic properties of biodegradable ILs composed of the 1-(alkoxycarbonyl)-3-alkylimidazolium cation ([C1COOCnC1im](+), n = 1, 2, 4) coupled with [Br](-), [NO3](-), [BF4](-), [PF6](-), [TfO](-), and [Tf2N](-) are explored using the molecular dynamics (MD) simulations and quantum theory of atoms in molecules (QTAIM) at 400 K. Formation of the intramolecular H bonds between O atoms of the ester group and H atoms of the imidazolium ring as well as the nearest H atom of the alkyl chain to the ester group are disclosed from reduced density gradient (RDG) results...
October 25, 2016: Journal of Physical Chemistry. B
Mohammad Goli, Shant Shahbazian
Recently, it has been demonstrated that the domain-averaged exchange-correlation energies, V(xc) , are capable of tracing the covalent character of atom-atom interactions unequivocally and thus pave the way for detailed bonding analysis within the context of the quantum theory of atoms in molecules (QTAIM) [M. García-Revilla, E. Francisco, P. L. Popelier, A. Martín Pendás, ChemPhysChem 2013, 14, 1211-1218]. Herein, the concept of V(xc) is extended within the context of the newly developed multicomponent QTAIM (MC-QTAIM)...
October 25, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Yiqian Cui, Junyou Shi, Zili Wang
The centers and radii of radial basis functions (RBFs) greatly affect the approximation capability of RBF networks (RBFNs). Traditional statistics-based approaches are widely used, but they may lack adaptivity to different data structures. Quantum clustering (QC), derived from quantum mechanics and the Schrödinger equation, demonstrates excellent capability in finding the structure and conformity toward data distribution. In this paper, a novel neural networks model called quantum local potential function networks (QLPFNs) is proposed...
October 20, 2016: IEEE Transactions on Neural Networks and Learning Systems
Adrian N Beyer, Jeremy O Richardson, Peter J Knowles, Judith Rommel, Stuart C Althorpe
The instanton method obtains approximate tunneling rates from the minimum-action path (known as the instanton) linking reactants to the products at a given temperature. An efficient way to find the instanton is to search for saddle-points on the ring-polymer potential surface, which is obtained by expressing the quantum Boltzmann operator as a discrete path-integral. Here we report a practical implementation of this ring-polymer form of instanton theory into the Molpro electronic-structure package, which allows the rates to be computed on-the-fly, without the need for a fitted analytic potential-energy surface...
October 24, 2016: Journal of Physical Chemistry Letters
Rui-Qin Zhang, Yan-Ling Zhao, Fei Qi, Klaus Hermann, Michel A Van Hove
Rotation-inducing torque is ubiquitous in many molecular systems. We present a straightforward theoretical method based on forces acting on atoms and obtained from atomistic quantum mechanics calculations to quickly and qualitatively determine whether a molecule or sub-unit thereof has a tendency to rotate and, if so, around which axis and in which sense: clockwise or counterclockwise. The method also indicates which atoms, if any, are predominant in causing the rotation. Our computational approach can in general efficiently provide insights into the internal rotational degrees of freedom of all molecules and help to theoretically screen or modify them in advance of experiments or to efficiently guide a detailed analysis of their rotational behavior with more extensive computations...
October 24, 2016: Physical Chemistry Chemical Physics: PCCP
Ganna Gryn'ova, Michelle L Coote, Clemence Corminboeuf
The electronic configuration of the molecule is the foundation of its structure and reactivity. The spin state is one of the key characteristics arising from the ordering of electrons within the molecule's set of orbitals. Organic molecules that have open-shell ground states and interesting physicochemical properties, particularly those influencing their spin alignment, are of immense interest within the up-and-coming field of molecular electronics. In this advanced review, we scrutinize various qualitative rules of orbital occupation and spin alignment, viz...
November 2015: Wiley Interdisciplinary Reviews. Computational Molecular Science
Abdulkadir Kocak, Ismail Erol, Muslum Yildiz, Hatice Can
Developing small compound based drugs targeting the β-secretase (BACE) enzyme is one of the most promising strategies in treatment of the Alzheimer's disease. As the enzyme shows the activity based on the acid-base reaction at a very narrow pH range, the protonation state of aspartic acids with the residue number 32 and 228 (Asp32 and Asp228), which forms the active site dyad, along with the protonation state of the ligand (substrate or inhibitor) play very critical role in interactions between the ligand and enzyme...
October 17, 2016: Journal of Molecular Graphics & Modelling
Kevin Kalisz, Ji Buethe, Sachin S Saboo, Suhny Abbara, Sandra Halliburton, Prabhakar Rajiah
Computed tomography is vulnerable to a wide variety of artifacts, including patient- and technique-specific artifacts, some of which are unique to imaging of the heart. Motion is the most common source of artifacts and can be caused by patient, cardiac, or respiratory motion. Cardiac motion artifacts can be reduced by decreasing the heart rate and variability and the duration of data acquisition; adjusting the placement of the data window within a cardiac cycle; performing single-heartbeat scanning; and using multisegment reconstruction, motion-correction algorithms, and electrocardiographic editing...
October 21, 2016: Radiographics: a Review Publication of the Radiological Society of North America, Inc
Dominik S Wild, Sarang Gopalakrishnan, Michael Knap, Norman Y Yao, Mikhail D Lukin
Adiabatic quantum algorithms represent a promising approach to universal quantum computation. In isolated systems, a key limitation to such algorithms is the presence of avoided level crossings, where gaps become extremely small. In open quantum systems, the fundamental robustness of adiabatic algorithms remains unresolved. Here, we study the dynamics near an avoided level crossing associated with the adiabatic quantum search algorithm, when the system is coupled to a generic environment. At zero temperature, we find that the algorithm remains scalable provided the noise spectral density of the environment decays sufficiently fast at low frequencies...
October 7, 2016: Physical Review Letters
Tobias Dornheim, Simon Groth, Travis Sjostrom, Fionn D Malone, W M C Foulkes, Michael Bonitz
We perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas in the thermodynamic limit. By combining QMC data with the linear response theory, we are able to remove finite-size errors from the potential energy over the substantial parts of the warm dense regime, overcoming the deficiencies of the existing finite-size corrections by Brown et al. [Phys. Rev. Lett. 110, 146405 (2013)]. Extensive new QMC results for up to N=1000 electrons enable us to compute the potential energy V and the exchange-correlation free energy F_{xc} of the macroscopic electron gas with an unprecedented accuracy of |ΔV|/|V|,|ΔF_{xc}|/|F|_{xc}∼10^{-3}...
October 7, 2016: Physical Review Letters
Koichi Hattori, Yi Yin
We investigate novel transport phenomena in a chiral fluid originated from an interplay between a vorticity and strong magnetic field, which induces a redistribution of vector charges in the system and an axial current along the magnetic field. The corresponding transport coefficients are obtained from an energy-shift argument for the chiral fermions in the lowest Landau level due to a spin-vorticity coupling and also from diagrammatic computations on the basis of the linear response theory. Based on consistent results from both methods, we observe that the transport coefficients are proportional to the anomaly coefficient and are independent of temperature and chemical potential...
October 7, 2016: Physical Review Letters
David A Mazziotti
A central challenge of physics is the computation of strongly correlated quantum systems. The past ten years have witnessed the development and application of the variational calculation of the two-electron reduced density matrix (2-RDM) without the wave function. In this Letter we present an orders-of-magnitude improvement in the accuracy of 2-RDM calculations without an increase in their computational cost. The advance is based on a low-rank, dual formulation of an important constraint on the 2-RDM, the T2 condition...
October 7, 2016: Physical Review Letters
Giuseppe Lanza, Maria A Chiacchio
Exploration of interfacial hydration networks of zwitterion and non-ionized trialanine has been performed using DFT-M062X quantum chemical computations explicitly considering up to 41 water molecules. The step-by-step water molecules peptide surrounding, carried out for unfolded extended (β), polyproline II (PPII) conformations reveals the crucial importance of explicit solvent effects in stabilizing the zwitterion form and the left-handed PPII-helix ubiquitously found at room temperature for short polyalanines...
October 21, 2016: Journal of Physical Chemistry. B
Yin-Shan Meng, Shang-Da Jiang, Bing-Wu Wang, Song Gao
Single-molecule magnets (SMMs) can retain their magnetization status preferentially after removal of the magnetic field below a certain temperature. The unique property, magnetic bistable status, enables the molecule-scale SMM to become the next-generation high-density information storage medium. SMMs' new applications are also involved in high-speed quantum computation and molecular spintronics. The development of coordination chemistry, especially in transition metal (3d) and lanthanide (4f) complexes, diversifies SMMs by introducing new ones...
October 21, 2016: Accounts of Chemical Research
Qi Wie, Yudong Cao, Sabre Kais, Bretislav Friedrich, Dudley Herschbach
We investigate several aspects of realizing quantum computation using entangled polar molecules in pendular states. Quantum algorithms typically start from a product state |00⋯0⟩ and we show that up to a negligible error, the ground states of polar molecule arrays can be considered as the unentangled qubit basis state |00⋯0⟩ . This state can be prepared by simply allowing the system to reach thermal equilibrium at low temperature (<1 mK). We also evaluate entanglement, characterized by concurrence of pendular state qubits in dipole arrays as governed by the external electric field, dipole-dipole coupling and number N of molecules in the array...
October 21, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Abel Santos, Cheryl Suwen Law, Dominique Wong Chin Lei, Taj Pereira, Dusan Losic
In this study, we present an advanced nanofabrication approach to produce gradient-index photonic crystal structures based on nanoporous anodic alumina. An apodization strategy is for the first time applied to a sinusoidal pulse anodisation process in order to engineer the photonic stop band of nanoporous anodic alumina (NAA) in depth. Four apodization functions are explored, including linear positive, linear negative, logarithmic positive and logarithmic negative, with the aim of finely tuning the characteristic photonic stop band of these photonic crystal structures...
October 21, 2016: Nanoscale
Chang Woo Kim, Young Min Rhee
Constructing a reliable potential energy surface (PES) is a key step toward computationally studying chemical dynamics of any molecular system. The interpolation scheme is a useful tool that can closely follow the accuracy of quantum chemical means at a dramatically reduced computational cost. However, applying interpolation for building a PES of a large molecule is not a straightforward black-box approach, as it frequently encounters practical difficulties associated with its large dimensionality. Here, we present detailed courses of applying interpolation toward building a PES of a large chromophore molecule...
October 19, 2016: Journal of Chemical Theory and Computation
Vahid Sokhanvaran, Saeid Yeganegi
The quantum mechanics (QM) method and Grand Canonical Monte Carlo (GCMC) simulations were performed to study the effect of lithium cation doping on the adsorption and separation of CO2, CH4 and H2 on 2-fold interwoven metal-organic framework (MOF) Zn2(NDC)2(diPyNI). The second order Moller-Plesset (MP2) calculations on the (Li+-diPyNI) cluster model showed that the energetically most favorable lithium binding site is above the pyridine ring side and at a distance of 1.817 Å from the oxygen atom. The results revealed that the adsorption capacity of Zn2(NDC)2(diPyNI) for carbon dioxide is higher than that of hydrogen and methane at room temperature...
October 19, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
A K Sivadasan, Chirantan Singha, A Bhattacharyya, Sandip Dhara
The observation of interface (IF) phonon modes in the recorded Raman spectra of c-plane oriented [AlN/GaN]20 and [Al0.35Ga0.65N/Al0.55Ga0.45N]20 multi-quantum well (MQW) structures grown via plasma assisted molecular beam epitaxy is reported. The nominal shift in the IF phonon mode of E1 symmetry for [Al0.35Ga0.65N/Al0.55Ga0.45N]20 compared to that of the [AlN/GaN]20 MQW structure is understood on the basis of change in dielectric constants (εm) of the surrounding medium. The presence of buffer layers in [Al0...
October 19, 2016: Physical Chemistry Chemical Physics: PCCP
Federica Lanni, Andrea Carotti, Roccaldo Sardella, Antonio Macchiarulo, Lucia Pucciarini, Benedetto Natalini
In the last few decades, there has been a significant increase in the development of chiral compounds. Thus, access to enantiomerically pure compounds is currently a major focus of pharmaceutical research and, in particular, chiral HPLC separations have gained great importance for semi-preparative and industrial isolation of enantiopure compounds. Chemoinformatic procedures as well as molecular modelling and quantum chemistry techniques can be successfully applied to address chirality related problems especially when enantiomerically pure reference standards are missing...
October 18, 2016: Mini Reviews in Medicinal Chemistry
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