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Quantum computer

Alex Monràs, Gael Sentís, Peter Wittek
In supervised learning, an inductive learning algorithm extracts general rules from observed training instances, then the rules are applied to test instances. We show that this splitting of training and application arises naturally, in the classical setting, from a simple independence requirement with a physical interpretation of being nonsignaling. Thus, two seemingly different definitions of inductive learning happen to coincide. This follows from the properties of classical information that break down in the quantum setup...
May 12, 2017: Physical Review Letters
Yu He, X Ding, Z-E Su, H-L Huang, J Qin, C Wang, S Unsleber, C Chen, H Wang, Y-M He, X-L Wang, W-J Zhang, S-J Chen, C Schneider, M Kamp, L-X You, Z Wang, S Höfling, Chao-Yang Lu, Jian-Wei Pan
Boson sampling is a problem strongly believed to be intractable for classical computers, but can be naturally solved on a specialized photonic quantum simulator. Here, we implement the first time-bin-encoded boson sampling using a highly indistinguishable (∼94%) single-photon source based on a single quantum-dot-micropillar device. The protocol requires only one single-photon source, two detectors, and a loop-based interferometer for an arbitrary number of photons. The single-photon pulse train is time-bin encoded and deterministically injected into an electrically programmable multimode network...
May 12, 2017: Physical Review Letters
Andrea Coladangelo, Koon Tong Goh, Valerio Scarani
Quantum technologies promise advantages over their classical counterparts in the fields of computation, security and sensing. It is thus desirable that classical users are able to obtain guarantees on quantum devices, even without any knowledge of their inner workings. That such classical certification is possible at all is remarkable: it is a consequence of the violation of Bell inequalities by entangled quantum systems. Device-independent self-testing refers to the most complete such certification: it enables a classical user to uniquely identify the quantum state shared by uncharacterized devices by simply inspecting the correlations of measurement outcomes...
May 26, 2017: Nature Communications
Hans Choi, Harry J Shirley, Paul A Hume, Margaret A Brimble, Daniel P Furkert
The unexpected synthesis of industrially important N-vinyl amides directly from aldehydes and α,β-unsaturated N-vinyl amides from esters is reported. This reaction probably proceeds through an initial [3+2] azide-enolate cycloaddition involving a vinyl azide generated in situ. A survey of the reaction scope and preliminary mechanistic findings supported by quantum computational analysis are reported, with implications for the future development of atom-efficient amide synthesis. Intriguingly, this study suggests that (cautious) reevaluation of azidoethene as a synthetic reagent may be warranted...
May 23, 2017: Angewandte Chemie
Taras Leonidovych Petrenko, V Bryksa
At present nitrogen-vacancy (NV) complex in diamond is the most promising defect for application in the area of quantum computing. This provides a stimulus for extensive search of another defects in semiconductors with similar properties. Recently it was shown that N$_{C}$V$_{Si}$ defect complex in SiC is perspective for this goal as well. In the present work we perform comparative \textit{ab initio} studies of NV complexes in diamond and 3\textit{C}-SiC. We focus both on radiospectroscopic characterization of these defects and on calculation of equilibrium concentration of complexes in irradiated crystals...
May 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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No abstract text is available yet for this article.
May 24, 2017: Nature
Johann V Pototschnig, Florian Lackner, Andreas W Hauser, Wolfgang E Ernst
Electronic excitations of an electron bound to an alkali metal ion inside a droplet of superfluid (4)He are computed via a combination of helium density functional theory and the numerical integration of the Schrödinger equation for a single electron in a modified, He density dependent atomic pseudopotential. The application of a spectral method to the radial part of the valence electron wavefunction allows the computation of highly excited Rydberg states. For low principal quantum numbers, the energy required to push the electron outward is larger than the solvation energy of the ion...
May 25, 2017: Physical Chemistry Chemical Physics: PCCP
Toshihiko Maeyama, Takuto Shimamori, Asuka Fujii
Excess-electron binding to dimers and trimers of secondary amide molecules was studied by a combination of photoelectron spectroscopy and theoretical calculations. Vertical detachment energies (VDEs) of the cluster anions were measured in the range of a few hundred meV. We found a tendency for VDE to decline with extension of alkyl side-chains. It was fairly reproduced by results of quantum chemical calculations based on density functional theory. For the optimized structures of the cluster anions, the excess electron is located diffusively around the dangling NH group of the hydrogen-bond acceptor molecule...
May 24, 2017: Journal of Physical Chemistry. A
Nguyen Ngoc Ha, Le Minh Cam, Nguyen Thi Thu Ha, Bee-Min Goh, Martin Saunders, Zhong-Tao Jiang, Mohammednoor Altarawneh, Bogdan Z Dlugogorski, Mohanad El-Harbawi, Chun-Yang Yin
The prevalence of global arsenic groundwater contamination has driven widespread research on developing effective treatment systems including adsorption using various sorbents. The uptake of arsenic-based contaminants onto established sorbents such as activated carbon (AC) can be effectively enhanced via immobilization/impregnation of iron-based elements on the porous AC surface. Recent suggestions that AC pores structurally consist of an eclectic mix of curved fullerene-like sheets may affect the arsenic adsorption dynamics within the AC pores and is further complicated by the presence of nano-sized iron-based elements...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Marcin Matusiak, J R Cooper, Dariusz Kaczorowski
Topological semimetals are systems in which conduction and valence bands cross each other and the crossings are protected by topological constraints. These materials provide intriguing tests for fundamental theories, while their unique physical properties promise a wide range of possible applications in low-power spintronics, optoelectronics, quantum computing and green energy harvesting. Here we report our study of the thermoelectric power of single-crystalline ZrSiS that is believed to be a topological nodal-line semimetal...
May 23, 2017: Nature Communications
Jerome T Mlack, Atikur Rahman, Gopinath Danda, Natalia Drichko, Sarah Friedensen, Marija Drndic, Nina Markovic
Topologically protected states in combination with superconductivity hold great promise for quantum computing applications, but the progress on electrical transport measurements in such systems has been impeded by the difficulty of fabricating devices with reliable electrical contacts. We find that superconductivity can be patterned directly into Bi$_2$Se$_3$ nanostructures by local doping with palladium. Superconducting regions are defined by depositing palladium on top of the nanostructures using electron beam lithography, followed by in-situ annealing...
May 23, 2017: ACS Nano
Ofer Reany, Amanda Li, Maayan Yefet, Michael K Gilson, Ehud Keinan
This study reports on the remarkable attractive interaction between organic azides and the portal carbonyls of cucurbiturils. Five homologous bis-α,ω-azidoethylammonium alkanes were prepared, where the number of methylene groups between the ammonium groups ranges from 4 to 8. Their interactions with cucurbit[6]uril were studied by NMR, IR and X-ray crystallography, and by computational methods. Remarkably, while the distance between the portal plane and most atoms at the guest end groups increase progressively with the molecular size, the β-nitrogen atoms maintain a constant distance from the portal plane in all homologs, pointing at a strong attractive interaction between the azide group and the portal...
May 23, 2017: Journal of the American Chemical Society
Bing Gu, Ignacio Franco
A hybrid method is proposed to propagate system-bath quantum dynamics that use both basis functions and coupled quantum trajectories. In it, the bath is represented with an ensemble of Bohmian trajectories while the system degrees of freedom are accounted through reduced density matrices. By retaining the Hilbert space structure for the system, the method is able to capture interference processes that are challenging to describe in Bohmian dynamics due to singularities that these processes introduce in the quantum potential...
May 21, 2017: Journal of Chemical Physics
Mohammad Bagher Gholivand, Hossein Peyman, Khodayar Gholivand, Hamideh Roshanfekr, Avat Arman Taherpour, Rouhollah Yaghoubi
Fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, circular dichroism spectroscopy, viscometry, cyclic voltammetry, and differential pulse voltammetry were applied to investigate the competitive interaction of DNA with the three new cycloalkyl α-aminobisphosphonates (D1-D3) and spectroscopic probe, neutral red dye, and Hoechst (HO), in a Tris-hydrogen chloride buffer (pH 7.4). The spectroscopic and voltammetric studies showed that the groove binding mode of interaction is predominant in the solution containing DNA and α-aminobisphosphonates...
May 19, 2017: DNA and Cell Biology
Patricia A Hunt
Hydrogen bonding (H-bonding) is an important and very general phenomenon. H-bonding is part of the basis of life in DNA, key in controlling the properties of water and ice, and critical to modern applications such as crystal engineering, catalysis applications, pharmaceutical and agrochemical development. H-bonding also plays a significant role for many ionic liquids (IL), determining the secondary structuring and affecting key physical parameters. ILs exhibit a particularly diverse and wide range of traditional as well as non-standard forms of H-bonding, in particular the doubly ionic H-bond is important...
June 2017: Topics in Current Chemistry (Journal)
Alfredo Aguado, Octavio Roncero, Alexandre Zanchet, Marcelino Agúndez, José Cernicharo
The impact of the photodissociation of HCN and HNC isomers is analyzed in different astrophysical environments. For this purpose, the individual photodissociation cross section of HCN and HNC isomers have been calculated in the 7-13.6 eV photon energy range for a temperature of 10 K. These calculations are based on the ab initio calculation of three-dimensional adiabatic potential energy surfaces of the 21 lower electronic states. The cross sections are then obtained using a quantum wave packet calculation of the rotational transitions needed to simulate a rotational temperature of 10 K...
March 20, 2017: Astrophysical Journal
Parinaz Aleahmad, Mercedeh Khajavikhan, Demetrios Christodoulides, Patrick LiKamWa
On-chip photonic networks hold great promise for enabling next-generation high speed computation and communication systems. It is currently envisioned that future integrated photonic networks will be capable of processing dense digital information on a single monolithic platform by involving a multitude of optical components ranging from lasers to modulators, to routers, interconnects and detectors. Among the possible functionalities to be incorporated in such arrangements is the ability to route information in a unidirectional way among N-ports - a capability typically afforded through the use of optical circulators...
May 18, 2017: Scientific Reports
Alberto Baiardi, Lorenzo Paoloni, Vincenzo Barone, Viatcheslav G Zakrzewski, Joseph Vincent Ortiz
The analysis of photoelectron spectra is usually facilitated by quantum mechanical simulations. Due to the recent improvement of experimental techniques, the resolution of experimental spectra is rapidly increasing, and the inclusion of vibrational effects is usually mandatory to obtain a reliable reproduction of the spectra. With the aim of defining a robust computational protocol, a general time-independent formulation to compute different kinds of vibrationally-resolved electronic spectra has been generalized to support also photoelectron spectroscopy...
May 18, 2017: Journal of Chemical Theory and Computation
Badrosadat Seyedhosseini, Mohammad Izadyar, Mohammad Reza Housaindokht
Hydrogen sulfide (H2S) and carbon dioxide (CO2) adsorption on a series of the aliphatic amino acid ionic liquids (AAILs) composed of N7,N9- dimethyladeninium cation with amino acid anions (AA= Gly, Ala, Val, Leu and Ile) as the functionalized ILs with dual groups of amine have been investigated. Based on the obtained data, the possible sites of H2S adsorption are twice as CO2 on the ionic liquids and also the average adsorption energy of H2S (∆E=-51.5 kJ.mol-1) in the most stable region of adsorption is twice greater than that of CO2 (∆E=-25...
May 18, 2017: Journal of Physical Chemistry. A
Jörg Behler
Modern simulation techniques have reached a level of maturity, which allows addressing a wide range of problems in chemistry and materials science. Unfortunately, the application of first principles methods with predictive power is still limited to rather small systems, and in spite of the rapid evolution of computer hardware no fundamental change of this situation can be expected. Consequently, to reach an atomic level understanding of complex systems, the development of more efficient but equally reliable atomistic potentials has received considerable attention in recent years...
May 18, 2017: Angewandte Chemie
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