The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Fernando G S L Brandao - One of the best experts on this subject based on the ideXlab platform.
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quantum Gibbs samplers the commuting case
Communications in Mathematical Physics, 2016Co-Authors: Michael J Kastoryano, Fernando G S L BrandaoAbstract:We analyze the problem of preparing quantum Gibbs states of lattice spin Hamiltonians with local and commuting terms on a quantum computer and in nature. Our central result is an equivalence between the behavior of correlations in the Gibbs state and the mixing time of the semigroup which drives the system to thermal equilibrium (the Gibbs sampler). We introduce a framework for analyzing the correlation and mixing properties of quantum Gibbs states and quantum Gibbs samplers, which is rooted in the theory of non-commutative \({\mathbb{L}_p}\) spaces. We consider two distinct classes of Gibbs samplers, one of them being the well-studied Davies generator modelling the dynamics of a system due to weak-coupling with a large Markovian environment. We show that their spectral gap is independent of system size if, and only if, a certain strong form of clustering of correlations holds in the Gibbs state. Therefore every Gibbs state of a commuting Hamiltonian that satisfies clustering of correlations in this strong sense can be prepared efficiently on a quantum computer. As concrete applications of our formalism, we show that for every one-dimensional lattice system, or for systems in lattices of any dimension at temperatures above a certain threshold, the Gibbs samplers of commuting Hamiltonians are always gapped, giving an efficient way of preparing the associated Gibbs states on a quantum computer.
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quantum Gibbs samplers the commuting case
arXiv: Quantum Physics, 2014Co-Authors: Michael J Kastoryano, Fernando G S L BrandaoAbstract:We analyze the problem of preparing quantum Gibbs states of lattice spin Hamiltonians with local and commuting terms on a quantum computer and in nature. Our central result is an equivalence between the behavior of correlations in the Gibbs state and the mixing time of the semigroup which drives the system to thermal equilibrium (the Gibbs sampler). We introduce a framework for analyzing the correlation and mixing characteristics of quantum Gibbs states and quantum Gibbs samplers, which is rooted in the theory of non-commutative Lp spaces. We consider two distinct classes of Gibbs samplers, one of which being the well-studied Davies generators modelling the dynamics on the system due to weak-coupling with a large Markovian environment. We show that their gap is independent of system size if, and only if, a certain strong form of clustering of correlations holds in the Gibbs state. As concrete applications of our formalism, we show that for every one-dimensional lattice system, or for systems in lattices of any dimension at high enough temperatures, the Gibbs samplers of commuting Hamiltonians are always gapped, giving an efficient way of preparing these states on a quantum computer.
Anne Gelb - One of the best experts on this subject based on the ideXlab platform.
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reducing the Gibbs ringing artifact in mri scans while maintaining tissue boundary integrity
International Symposium on Biomedical Imaging, 2002Co-Authors: Anne Gelb, Rick ArchibaldAbstract:Gibbs ringing is a well known artifact that effects reconstruction of images having discontinuities. This is a problem in the reconstruction of magnetic resonance imaging (MRI) data due to the many different tissues normally present in each scan. The Gibbs ringing artifact manifests itself at the boundaries of the tissues, making it difficult to determine the structure of the brain tissue. The Gegenbauer reconstruction method has been shown to effectively eliminate the effects of Gibbs ringing in other applications. This paper presents the application of the Gegenbauer reconstruction method to neuro-imaging.
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a method to reduce the Gibbs ringing artifact in mri scans while keeping tissue boundary integrity
IEEE Transactions on Medical Imaging, 2002Co-Authors: Rick Archibald, Anne GelbAbstract:Gibbs ringing is a well known artifact that effects reconstruction of images having discontinuities. This is a problem in the reconstruction of magnetic resonance imaging (MRI) data due to the many different tissues normally present in each scan. The Gibbs ringing artifact manifests itself at the boundaries of the tissues, making it difficult to determine the structure of the brain tissue. The Gegenbauer reconstruction method has been shown to effectively eliminate the effects of Gibbs ringing in other applications. This paper presents the application of the Gegenbauer reconstruction method to neuro-imaging.
Esam A Gomaa - One of the best experts on this subject based on the ideXlab platform.
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thermodynamics of the solvation of potassium chromate in mixed dmf h 2 o solvents at 301 15 k
American Journal of Systems Science, 2014Co-Authors: Esam A GomaaAbstract:The Gibbs free energies for K2CrO4 were evaluated in mixed dimethylformamide (DMF)-H2O solvents at 301.15 K from the experimental solubility measurements. From the experimental solubility data also the ionic radii of potassium and chromate ions are evaluated . The total free energy of the salt is divided into its individual contribution in the mixtures used. Libration Gibbs free energy for moving K2CrO4 from standard gas state to standard solution state was calculated according to specific cycle for the solvation process using the solubility product. Also the lattice energy for solid K2CrO4 (cr) was also calculated and used for further evaluation. The conventional Gibbs free energies for the cation (K + ) and the anion (CrO4 2- ) were estimated theoretically and also the Gibbs free energy of CrO4 2- gas was evaluated and all values were discussed.
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Gibbs free energies for the solvation of potassium chlorate in mixed dmf h2o solvents at 301 15 k
European Chemical Bulletin, 2013Co-Authors: Esam A Gomaa, E A MahmoudAbstract:Normal 0 The Gibbs free energies for KClO 3 were evaluated in mixed dimethyeformamide (DMF)-H 2 O solvents at 301.15 K from the experimental solubility measurements. From the experimental the ionic radii ratio of potassium to chlorate ions, the total free energy of the salt is divided into its individual contribution in the mixtures used. Libration Gibbs free energy for moving KClO 3 from standard gas state to standard solution state was calculated according to specific cycle for the solvation process using the solubility product. Also the lattice energy for solid KClO 3 (Cr) was also calculated and used for further evaluation. The conventional Gibbs free energies for the cation (K + ) and the anion (ClO 3 - ) were estimated theoretically and also the Gibbs free energy of ClO 3 - gas was evaluated and all values were discussed.
Michael J Kastoryano - One of the best experts on this subject based on the ideXlab platform.
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quantum Gibbs samplers the commuting case
Communications in Mathematical Physics, 2016Co-Authors: Michael J Kastoryano, Fernando G S L BrandaoAbstract:We analyze the problem of preparing quantum Gibbs states of lattice spin Hamiltonians with local and commuting terms on a quantum computer and in nature. Our central result is an equivalence between the behavior of correlations in the Gibbs state and the mixing time of the semigroup which drives the system to thermal equilibrium (the Gibbs sampler). We introduce a framework for analyzing the correlation and mixing properties of quantum Gibbs states and quantum Gibbs samplers, which is rooted in the theory of non-commutative \({\mathbb{L}_p}\) spaces. We consider two distinct classes of Gibbs samplers, one of them being the well-studied Davies generator modelling the dynamics of a system due to weak-coupling with a large Markovian environment. We show that their spectral gap is independent of system size if, and only if, a certain strong form of clustering of correlations holds in the Gibbs state. Therefore every Gibbs state of a commuting Hamiltonian that satisfies clustering of correlations in this strong sense can be prepared efficiently on a quantum computer. As concrete applications of our formalism, we show that for every one-dimensional lattice system, or for systems in lattices of any dimension at temperatures above a certain threshold, the Gibbs samplers of commuting Hamiltonians are always gapped, giving an efficient way of preparing the associated Gibbs states on a quantum computer.
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quantum Gibbs samplers the commuting case
arXiv: Quantum Physics, 2014Co-Authors: Michael J Kastoryano, Fernando G S L BrandaoAbstract:We analyze the problem of preparing quantum Gibbs states of lattice spin Hamiltonians with local and commuting terms on a quantum computer and in nature. Our central result is an equivalence between the behavior of correlations in the Gibbs state and the mixing time of the semigroup which drives the system to thermal equilibrium (the Gibbs sampler). We introduce a framework for analyzing the correlation and mixing characteristics of quantum Gibbs states and quantum Gibbs samplers, which is rooted in the theory of non-commutative Lp spaces. We consider two distinct classes of Gibbs samplers, one of which being the well-studied Davies generators modelling the dynamics on the system due to weak-coupling with a large Markovian environment. We show that their gap is independent of system size if, and only if, a certain strong form of clustering of correlations holds in the Gibbs state. As concrete applications of our formalism, we show that for every one-dimensional lattice system, or for systems in lattices of any dimension at high enough temperatures, the Gibbs samplers of commuting Hamiltonians are always gapped, giving an efficient way of preparing these states on a quantum computer.
Rick Archibald - One of the best experts on this subject based on the ideXlab platform.
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reducing the Gibbs ringing artifact in mri scans while maintaining tissue boundary integrity
International Symposium on Biomedical Imaging, 2002Co-Authors: Anne Gelb, Rick ArchibaldAbstract:Gibbs ringing is a well known artifact that effects reconstruction of images having discontinuities. This is a problem in the reconstruction of magnetic resonance imaging (MRI) data due to the many different tissues normally present in each scan. The Gibbs ringing artifact manifests itself at the boundaries of the tissues, making it difficult to determine the structure of the brain tissue. The Gegenbauer reconstruction method has been shown to effectively eliminate the effects of Gibbs ringing in other applications. This paper presents the application of the Gegenbauer reconstruction method to neuro-imaging.
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a method to reduce the Gibbs ringing artifact in mri scans while keeping tissue boundary integrity
IEEE Transactions on Medical Imaging, 2002Co-Authors: Rick Archibald, Anne GelbAbstract:Gibbs ringing is a well known artifact that effects reconstruction of images having discontinuities. This is a problem in the reconstruction of magnetic resonance imaging (MRI) data due to the many different tissues normally present in each scan. The Gibbs ringing artifact manifests itself at the boundaries of the tissues, making it difficult to determine the structure of the brain tissue. The Gegenbauer reconstruction method has been shown to effectively eliminate the effects of Gibbs ringing in other applications. This paper presents the application of the Gegenbauer reconstruction method to neuro-imaging.
