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Quantum computer

F Mascherpa, A Smirne, S F Huelga, M B Plenio
In the study of open quantum systems, one of the most common ways to describe environmental effects on the reduced dynamics is through the spectral density. However, in many models this object cannot be computed from first principles and needs to be inferred on phenomenological grounds or fitted to experimental data. Consequently, some uncertainty regarding its form and parameters is unavoidable; this in turn calls into question the accuracy of any theoretical predictions based on a given spectral density. Here, we focus on the spin-boson model as a prototypical open quantum system, find two error bounds on predicted expectation values in terms of the spectral density variation considered, and state a sufficient condition for the strongest one to apply...
March 10, 2017: Physical Review Letters
Wolfgang A Vitale, Emanuele A Casu, Arnab Biswas, Teodor Rosca, Cem Alper, Anna Krammer, Gia V Luong, Qing-T Zhao, Siegfried Mantl, Andreas Schüler, A M Ionescu
Steep-slope transistors allow to scale down the supply voltage and the energy per computed bit of information as compared to conventional field-effect transistors (FETs), due to their sub-60 mV/decade subthreshold swing at room temperature. Currently pursued approaches to achieve such a subthermionic subthreshold swing consist in alternative carrier injection mechanisms, like quantum mechanical band-to-band tunneling (BTBT) in Tunnel FETs or abrupt phase-change in metal-insulator transition (MIT) devices...
March 23, 2017: Scientific Reports
Johannes Gooth, Mattias Borg, Heinz Schmid, Vanessa Schaller, Stephan Wirths, Kirsten E Moselund, Mathieu Luisier, Siegfried Karg, Heike Riel
Coherent interconnection of quantum bits remains an ongoing challenge in quantum information technology. Envisioned hardware to achieve this goal is based on semiconductor nanowire (NW) circuits, comprising individual NW devices that are linked through ballistic interconnects. However, maintaining the sensitive ballistic conduction and confinement conditions across NW intersections is a non-trivial problem. Here, we go beyond the characterization of a single NW device and demonstrate ballistic 1D quantum transport in InAs NW cross-junctions, monolithically integrated on Si...
March 23, 2017: Nano Letters
Nikhil Aggarwal, Archita Patnaik
Structure - property correlations in Rubrene (RB) colloidal J-aggregates were unravelled by steady state and time resolved spectroscopy in conjunction with excited state density functional calculations. The RB J-aggregate with a slippage angle θ = 30.4(0), estimated from the monomeric transition dipole moment directions, exhibited a broad FWHM of 1073 cm(-1) and a 5 nm red shifted absorption band carrying a transition dipole moment (M ⃗_(λagg )= 1.80 D) almost equivalent to the monomeric dye (M ⃗_(λmon )=1...
March 23, 2017: Journal of Physical Chemistry. B
P V Pyshkin, Da-Wei Luo, Jun Jing, J Q You, Lian-Ao Wu
No abstract text is available yet for this article.
March 23, 2017: Scientific Reports
Andreas Trabesinger
No abstract text is available yet for this article.
March 22, 2017: Nature
Raouf Dridi, Hedayat Alghassi
No abstract text is available yet for this article.
March 22, 2017: Scientific Reports
Mehdi D Esrafili, Soheila Asadollahi
In this work, we investigate the effect of a cation-π interaction on the cooperativity of X⋯N halogen bonds in PhX⋯NCX⋯NH3 complexes, where Ph=phenyl and X=Cl, Br, I. Molecular geometries and interaction energies of the resulting complexes are studied at the MP2/aug-cc-pVDZ(-PP) computational level. The mechanism of the cooperativity between halogen bonds is analyzed using parameters derived from the noncovalent index, quantum theory of atoms in molecules and natural bond orbital methodologies. It is found that the divalent cations (Be(2+), Mg(2+)) have a larger influence on the cooperativity of halogen bonds than monovalent ones (Li(+), Na(+))...
March 2, 2017: Journal of Molecular Graphics & Modelling
Norbert M Linke, Dmitri Maslov, Martin Roetteler, Shantanu Debnath, Caroline Figgatt, Kevin A Landsman, Kenneth Wright, Christopher Monroe
We run a selection of algorithms on two state-of-the-art 5-qubit quantum computers that are based on different technology platforms. One is a publicly accessible superconducting transmon device (www. RESEARCH: with limited connectivity, and the other is a fully connected trapped-ion system. Even though the two systems have different native quantum interactions, both can be programed in a way that is blind to the underlying hardware, thus allowing a comparison of identical quantum algorithms between different physical systems...
March 21, 2017: Proceedings of the National Academy of Sciences of the United States of America
Dayton Jon Vogel, Andrei Kryjevski, Talgat M Inerbaev, Dmitri S Kilin
Methyl-ammonium lead iodide perovskite (MAPbI3) is a promising material for photovoltaic devices. A modification of the MAPbI3 into confined nanostructures is expected to further increase efficiency of solar energy conversion. Photo-excited dynamic processes in a MAPbI3 quantum dot (QD) have been modeled by many-body perturbation theory and nonadiabatic dynamics. A photoexcitation is followed by either exciton cooling (EC), its radiative (RR) or non-radiative recombination (NRR), or multi-exciton generation (MEG) processes...
March 21, 2017: Journal of Physical Chemistry Letters
Pavel Majek, Jan Krupcik, Zachary S Breitbach, Milan K Dissanayake, Peter Kroll, Aaron A Ruch, LeGrande M Slaughter, Daniel W Armstrong
Dynamic high resolution liquid chromatography (DHPLC) was used to determine the kinetic and thermodynamic activation parameters of interconversion of three novel pentahelicene derivatives {3,5-bis(trifluoromethyl)benzo[i]pentahelicene, naphtho[1,2-i]pentahelicene and 4-methoxybenzo[i]pentahelicene}. DHPLC was performed on a chiral isopropyl - carbamate cyclofructan 6 (LARIHC CF6-P) column under normal phase conditions. Variation of the column temperature and flow rate was used to study the interconversion process...
December 21, 2016: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
Arndt R Finkelmann, Andreas H Göller, Gisbert Schneider
Machine learning models for site of metabolism (SoM) prediction offer the ability to identify metabolic soft spots in low molecular weight drug molecules at low computational cost and enable data-based reactivity prediction. SoM prediction is an atom classification problem. Successful construction of machine learning models requires atom representations that capture the reactivity-determining features of a potential reaction site. We have developed a descriptor scheme that characterizes an atom's steric and electronic environment and its relative location in the molecular structure...
March 21, 2017: ChemMedChem
C X Zhang, X G Qiu
Parity anomaly refers to the violation of coordinate reflection symmetry induced by the quantum fluctuations. It is proposed to exist in a graphene-like system with a finite bare mass for Dirac fermions, and manifests itself as a parity- violating quantum correction to the current of each species of fermions. Coulomb interaction greatly increases the fermion mass, and produces various types of excitons. Of particular interest is the ρ-exciton, which is directly connected to parity anomaly and can be generated by absorbing a specific photon...
March 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Vladimir S Bystrov, Igor K Bdikin, Maksim Silibin, Dmitry Karpinsky, Svitlana Kopyl, Ekaterina V Paramonova, Gil Goncalves
Molecular modeling of ferroelectric composites containing polyvinylidene fluoride (PVDF) and either graphene (G) or graphene oxide (GO) were performed using the semi-empirical quantum approximation PM3 in HyperChem. The piezo properties of the composites were analyzed and compared with experimental data obtained for P(VDF-TrFE)-GO films. Qualitative agreement was obtained between the results of the modeling and the experimental results in terms of the properties of the measured effective piezoelectric coefficient d 33eff and its decrease in the presence of G/GO in comparison with the average computed piezoelectric coefficient <d 33>...
April 2017: Journal of Molecular Modeling
Riccardo Spezia, Emilio Martínez-Nuñez, Saulo Vazquez, William L Hase
In this Introduction, we show the basic problems of non-statistical and non-equilibrium phenomena related to the papers collected in this themed issue. Over the past few years, significant advances in both computing power and development of theories have allowed the study of larger systems, increasing the time length of simulations and improving the quality of potential energy surfaces. In particular, the possibility of using quantum chemistry to calculate energies and forces 'on the fly' has paved the way to directly study chemical reactions...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Sonia Marggi Poullain, David V Chicharro, Luis Rubio-Lago, Alberto García-Vela, Luis Bañares
Chemical reaction dynamics and, particularly, photodissociation in the gas phase are generally studied using pump-probe schemes where a first laser pulse induces the process under study and a second one detects the produced fragments. Providing an efficient detection of ro-vibrationally state-selected photofragments, the resonance enhanced multiphoton ionization (REMPI) technique is, without question, the most popular approach used for the probe step, while non-resonant multiphoton ionization (NRMPI) detection of the products is scarce...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Francesca Peccati, Sebastian Mai, Leticia González
5-Bromouracil is a nucleobase analogue that can replace thymine in DNA strands and acts as a strong radiosensitizer, with potential applications in molecular biology and cancer therapy. Here, the deactivation of 5-bromouracil after ultraviolet irradiation is investigated in the singlet and triplet manifold by accurate quantum chemistry calculations and non-adiabatic dynamics simulations. It is found that, after irradiation to the bright ππ* state, three main relaxation pathways are, in principle, possible: relaxation back to the ground state, intersystem crossing (ISC) and C-Br photodissociation...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Vincenzo Aquilanti, Nayara Dantas Coutinho, Valter Henrique Carvalho-Silva
This article surveys the empirical information which originated both by laboratory experiments and by computational simulations, and expands previous understanding of the rates of chemical processes in the low-temperature range, where deviations from linearity of Arrhenius plots were revealed. The phenomenological two-parameter Arrhenius equation requires improvement for applications where interpolation or extrapolations are demanded in various areas of modern science. Based on Tolman's theorem, the dependence of the reciprocal of the apparent activation energy as a function of reciprocal absolute temperature permits the introduction of a deviation parameter d covering uniformly a variety of rate processes, from those where quantum mechanical tunnelling is significant and d < 0, to those where d > 0, corresponding to the Pareto-Tsallis statistical weights: these generalize the Boltzmann-Gibbs weight, which is recovered for d = 0...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Jérôme Hurst, Paul-Antoine Hervieux, Giovanni Manfredi
Using the phase-space formulation of quantum mechanics, we derive a four-component Wigner equation for a system composed of spin-[Formula: see text] fermions (typically, electrons) including the Zeeman effect and the spin-orbit coupling. This Wigner equation is coupled to the appropriate Maxwell equations to form a self-consistent mean-field model. A set of semiclassical Vlasov equations with spin effects is obtained by expanding the full quantum model to first order in the Planck constant. The corresponding hydrodynamic equations are derived by taking velocity moments of the phase-space distribution function...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Yi Zou, Fang Wang, Yan Wang, Wenjie Guo, Yihua Zhang, Qiang Xu, Yisheng Lai
Indoleamine 2,3-dioxygenase 1 (IDO1) is regarded as an attractive target for cancer immunotherapy. To rationalize the detailed interactions between IDO1 and its inhibitors at the atomic level, an integrated computational approach by combining molecular mechanics and quantum mechanics methods was employed in this report. Specifically, the binding modes of 20 inhibitors was initially investigated using the induced fit docking (IFD) protocol, which outperformed other two docking protocols in terms of correctly predicting ligand conformations...
March 14, 2017: European Journal of Medicinal Chemistry
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