1,029 research outputs found
Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
Quantum ESPRESSO is an integrated suite of computer codes for
electronic-structure calculations and materials modeling, based on
density-functional theory, plane waves, and pseudopotentials (norm-conserving,
ultrasoft, and projector-augmented wave). Quantum ESPRESSO stands for "opEn
Source Package for Research in Electronic Structure, Simulation, and
Optimization". It is freely available to researchers around the world under the
terms of the GNU General Public License. Quantum ESPRESSO builds upon
newly-restructured electronic-structure codes that have been developed and
tested by some of the original authors of novel electronic-structure algorithms
and applied in the last twenty years by some of the leading materials modeling
groups worldwide. Innovation and efficiency are still its main focus, with
special attention paid to massively-parallel architectures, and a great effort
being devoted to user friendliness. Quantum ESPRESSO is evolving towards a
distribution of independent and inter-operable codes in the spirit of an
open-source project, where researchers active in the field of
electronic-structure calculations are encouraged to participate in the project
by contributing their own codes or by implementing their own ideas into
existing codes.Comment: 36 pages, 5 figures, resubmitted to J.Phys.: Condens. Matte
Transport of Spin Qubits with Donor Chains under Realistic Experimental Conditions
The ability to transport quantum information across some distance can
facilitate the design and operation of a quantum processor. One-dimensional
spin chains provide a compact platform to realize scalable spin transport for a
solid-state quantum computer. Here, we model odd-sized donor chains in silicon
under a range of experimental non-idealities, including variability of donor
position within the chain. We show that the tolerance against donor placement
inaccuracies is greatly improved by operating the spin chain in a mode where
the electrons are confined at the Si-SiO interface. We then estimate the
required timescales and exchange couplings, and the level of noise that can be
tolerated to achieve high fidelity transport. We also propose a protocol to
calibrate and initialize the chain, thereby providing a complete guideline for
realizing a functional donor chain and utilizing it for spin transport.Comment: 19 pages, 12 figure
Infrared Energy Harvesting for Optoplasmonics from Nanostructured Metamaterials
Metamaterials exhibit unique optical resonance characteristics which permit precise engineering of energy pathways within a device. The ability of plasmonic nanostructures to guide electromagnetism offers a platform to reduce global dependence on fossil fuels by harvesting waste heat, which comprises 60% of generated energy around the world. Plasmonic metamaterials were hypothesized to support an exchange of energy between resonance modes, enabling generation of higher energy photons from waste infrared energy. Infrared irradiation of a metamaterial at the Fano coupling lattice resonance was anticipated to re-emit as higher energy visible light at the plasmon resonance. Photonic signals from harvested thermal energy could be used to power wearable medical monitors or off-grid excursions, for example. This thesis developed the design, fabrication, and characterization methods to realize nanostructured metamaterials which permit resonance exchange for infrared energy harvesting applications
- …