Search results for " Quantum"

The molecular structure of N-hydroxyurea

1996

Ab initio calculations were performed on the tautomers and conformers of N-hydroxyurea using a 6-31G** basis set. The minimum-energy structures have been found and the importance of the intramolecular hydrogen bond as the stabilizing factor was pointed out. © 1996 John Wiley & Sons, Inc.

Robust entanglement preparation against noise by controlling spatial indistinguishability

2019

Initialization of composite quantum systems into highly entangled states is usually a must to allow their use for quantum technologies. However, the presence of unavoidable noise in the preparation stage makes the system state mixed, thus limiting the possibility of achieving this goal. Here we address this problem in the context of identical particle systems. We define the entanglement of formation for an arbitrary state of two identical qubits within the operational framework of spatially localized operations and classical communication (sLOCC). We then introduce an entropic measure of spatial indistinguishability under sLOCC as an information resource. We show that spatial indistinguisha…

Categories, Quantum Computing, and Swarm Robotics: A Case Study

2022

The swarms of robots are examples of artificial collective intelligence, with simple individual autonomous behavior and emerging swarm effect to accomplish even complex tasks. Modeling approaches for robotic swarm development is one of the main challenges in this field of research. Here, we present a robot-instantiated theoretical framework and a quantitative worked-out example. Aiming to build up a general model, we first sketch a diagrammatic classification of swarms relating ideal swarms to existing implementations, inspired by category theory. Then, we propose a matrix representation to relate local and global behaviors in a swarm, with diagonal sub-matrices describing individual featur…

Using Applications and Tools to Visualize ab initio Calculations Performed in VASP

2018

Visualization of the results of the ab initio calculations is important for the analysis of these results. It improves the quality of the analysis by supplementing the plain numbers received as the output of the calculations with various graphical images and facilitates the analysis of the results. In addition to that visualization helps avoiding some mistakes or inconsistencies. Various tools have been used in this work to construct the unit cell models of the calculated lattices, to check and analyze the calculated lattice structure before and after the relaxation, to plot total and difference electron charge density maps.

Multimode entanglement in reconfigurable graph states using optical frequency combs

2017

Multimode entanglement is an essential resource for quantum information processing and quantum metrology. However, multimode entangled states are generally constructed by targeting a specific graph configuration. This yields to a fixed experimental setup that therefore exhibits reduced versatility and scalability. Here we demonstrate an optical on-demand, reconfigurable multimode entangled state, using an intrinsically multimode quantum resource and a homodyne detection apparatus. Without altering either the initial squeezing source or experimental architecture, we realize the construction of thirteen cluster states of various sizes and connectivities as well as the implementation of a secr…

A PH-functionalized polyphosphazene: a macromolecule with a highly flexible backbone.

2006

Comment on ``Friedel phases and phases of transmission amplitudes in quantum scattering systems" by T. Taniguchi and M. Buettiker

1999

We take a modified boundary condition at the dead end of a stub to simulate transmission zeroes being replaced by minima and then the discontinuous phase slip (or decrease) at the transmission zeroes are replaced by a continuous but rapid phase slip. The modified boundary condition can be continuously tuned to give the results of the stub with hard wall boundary condition at the dead end of stub. Even when the phase slip is continuous one can obtain information about the density of states in the stub region from the scattering phases.

Electron spectra in double quantum wells of different shapes

2022

We suggest a method for calculating electronic spectra in ordered and disordered semiconductor structures (superlattices) forming double quantum wells (QW). In our method, we represent the solution of Schr\"odinger equation for QW potential with the help of the solution of the corresponding diffusion equation. This is because the diffusion is the mechanism, which is primarily responsible for amorphization (disordering) of the QW structure, leading to so-called interface mixing. We show that the electron spectrum in such a structure depends on the shape of the quantum well, which, in turn, corresponds to an ordered or disordered structure. Namely, in a disordered substance, QW typically has …

Comparative classical and ab initio Molecular Dynamics study of molten and glassy germanium dioxide

2008

A Molecular Dynamics (MD) study of static and dynamic properties of molten and glassy germanium dioxide is presented. The interactions between the atoms are modelled by the classical pair potential proposed by Oeffner and Elliott (OE) [Oeffner R D and Elliott S R 1998, Phys. Rev. B, 58, 14791]. We compare our results to experiments and previous simulations. In addition, an ab initio method, the so-called Car-Parrinello Molecular Dynamics (CPMD), is applied to check the accuracy of the structural properties, as obtained by the classical MD simulations with the OE potential. As in a similar study for SiO2, the structure predicted by CPMD is only slightly softer than that resulting from the cl…

Engineering the molecular structure to optimize the spin Hall signal in organics

2020

In this study, by engineering the molecular structure, we optimize the spin Hall conductivity and the spin Hall angle in organics by more than five and three orders of magnitude, respectively. We identify two important characteristics of organic molecules, namely substitution of heavy elements and the torsion angles between constituent units of the polymer, which have significant effects on the spin Hall signal. These characteristics are directly related to the spin-orbit coupling and the energetic disorder, both of which offer a wide scope of chemical tunability in high-mobility polymers. We compute the spin Hall characteristics for easily synthesized molecules and identify candidates to e…