Search results for "Quantum"
showing 10 items of 9714 documents
Removing phase ambiguity in fiber-based interferometers for coherent time-bin operations
2019
Time is a practical and robust degree of freedom for the encoding of quantum information. Qubits encoded in so-called 'time-bins', allowing a discrete superposition of two potential arrival times, have their entanglement preserved even over long propagation distances in standard fiber networks [1]. Time has also been used for the preparation of more complex quantum systems, such as hyper-entangled and cluster states [2]. These qualities put time-bin encoding at the center of applications ranging from quantum state preparation through to quantum communications and information processing. One of the hallmarks of the scheme is that a nonlinear element has to be pumped with phase-coherent doubl…
Quantum Nanoplasmonic : from dressed atom picture to superradiance
2019
Controlling quantum emitters (atoms, molecules, quantum dots, etc.), light, and its interactions is a key issue for implementing devices for information optical processing at the quantum level. For example, controlling dynamics of emitters coupled to a high-Q cavity can be achieved through cavity quantum electrodynamics (cQED). Plasmonic structures hybrid system are of growing interest in the quantum control at the nanoscale because of their capability to confine light beyond the diffraction limit. However, its application appears notoriously limited in practical situations due to the intrinsic presence of numerous and lossy modes, which complicates the description and the interpretation of…
Ab initiothermodynamics ofBacSr(1−c)TiO3solid solutions
2005
Based on ab initio calculations for a number of the ${\mathrm{Ba}}_{\mathrm{c}}{\mathrm{Sr}}_{(1\ensuremath{-}\mathrm{c})}\mathrm{Ti}{\mathrm{O}}_{3}$ (BST) superlattices, we developed a thermodynamic approach to these solid solutions. In particular, we calculate the BST phase diagram and show that at relatively low temperatures (below $400\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $c=0.5$ and $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $c=0.1$) the spinodal decomposition of the solid solution occurs. As a result, we predict for small Ba concentrations formation of $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}$ nanoregions in a predominantly $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ matrix and …
Comparative Hybrid Hartree-Fock-DFT Calculations of WO2-Terminated Cubic WO3 as Well as SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (001) Surfaces
2021
We greatly acknowledge the financial support via the ERAF Project No. 1.1.1.1/18/A/073. Calculations were performed using Latvian Super Cluster (LASC), located in the Center of Excellence at Institute of Solid State Physics, the University of Latvia, which is supported by European Union Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under Grant Agreement No. 739508, project CAMART.
Systematic trends in YAlO3, SrTiO3, BaTiO3, BaZrO3 (001) and (111) surface ab initio calculations
2019
We greatly acknowledge the financial support via Latvian-Ukrainian Joint Research Project No. LV-UA/2018/2, Latvian Council of Science Grant No. 2018/2-0083 “Theoretical prediction of hybrid nanostructured photocatalytic materials for efficient water splitting”, Latvian Council of Science Grant No. 2018/1-0214 as well as ERAF Project No. 1.1.1.1/18/A/073.
Atomistic Simulations of the LaMnO3 (110) Polar Surface.
2003
The results of atomic structure calculations, with a focus on the surface relaxation and polarization, are presented for the LaMnO3 (110) O-terminated polar surface. We compare results of the classical shell model calculations for four possible terminations, including (1 × 2) (110) surface reconstruction, and demonstrate that the latter has the lowest surface energy. The surface energy is saturated only when six to eight near-surface atomic planes are relaxed which is accompanied by the considerable dipole moments perpendicular to the surface. Results are compared with those for iso-structural BaTiO3 (110) surfaces.
Ab Initio Calculations of Hydroxyl Impurities in CaF2
2012
OH– in CaF2 crystal and the (111) surface have been studied by using density functional theory (DFT) with hybrid exchange potentials, namely, DFT-B3PW. Three bulk and 20 surface OH– configurations ...
Ab Initio Calculations of SrTiO3 (111) Surfaces
2012
The paper presents the results of calculations of SrTiO3 polar (111) surface relaxations and energetics using the ab initio code CRYSTAL and a hybrid description of exchange and correlation. Using a hybrid B3LYP approach, the surface relaxation has been calculated for the two possible Ti and SrO3 SrTiO3 (111) surface terminations. For both Ti and SrO3-terminated SrTiO3 (111) surfaces upper layer atoms, with the sole exception of SrO3-terminated surface Sr atom, relax inwards. The calculated surface relaxation energy for Ti-terminated SrTiO3 (111) surface is almost five times larger, than the surface relaxation energy for SrO3-terminated SrTiO3 (111) surface. The surface energy for Ti-termin…
Theoretical Modelling of the Energy Surface (001) and Topology of CaZrO3 Perovskite
2015
I present the results of ab initio calculations of surface relaxations, rumplings, energetics, optical band gaps, and charge distribution for the CaZrO3 (001) surfaces using computer code CRYSTAL and a hybrid description of exchange and correlation. I consider both CaO and ZrO2-terminations of the CaZrO3 (001) surface. On the both CaO and ZrO2-terminated CaZrO3 (001) surfaces, I find that all upper and third layer atoms relax inwards, whereas all second layer atoms relax upwards. I predict a considerable increase of the Zr-O chemical bond covalency (0.102e) near the ZrO2-terminated CaZrO3 (001) surface relative to the CaZrO3 bulk (0.086e). My calculated CaO (0.87 eV) and ZrO2-terminated (1.…
Ab initio Calculations of Bulk and (001) Surface F-centers in ABO3 Perovskites
2021
We analyzed systematic trends in BaTiO 3, SrTiO 3 , PbZrO 3 and SrZrO 3 bulk as well as very rarely performed (001) surface F-center ab initio calculations. The nearest neighbor atomic displacements around the bulk F-center in the ABO 3 perovskites are considerably smaller than the relevant neighbor atomic displacements around the (001) surface $F$ -centers. The $F$ -center electrons are more delocalized for the ABO 3 perovskite (001) surface $F$ -center than for the bulk $F$ -center. Our calculated formation energy differences between the BaTiO 3 , SrTiO 3 , PbZrO 3 and SrZrO 3 bulk and its (001) surface $F$ -centers triggers the $F$ -center segregation from the bulk crystal towards the AB…