The Experts below are selected from a list of 1339731 Experts worldwide ranked by ideXlab platform
Gunter M Schutz - One of the best experts on this subject based on the ideXlab platform.
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real time Dynamics in spin 1 2 chains with adaptive time dependent density matrix renormalization group
Physical Review E, 2005Co-Authors: Dominique Gobert, Corinna Kollath, U Schollwock, Gunter M SchutzAbstract:: We investigate the influence of different interaction strengths and dimerizations on the magnetization transport in antiferromagnetic spin 1/2 XXZ chains. We focus on the Real-Time evolution of the inhomogeneous initial state |upward arrow... upward arrow downward arrow... downward arrow > in using the adaptive time-dependent density-matrix renormalization group (adaptive t-DMRG). Time scales accessible to us are of the order of 100 units of time measured in Planck's/J for almost negligible error in the observables. We find ballistic magnetization transport for small S(z) S(z) interaction and arbitrary dimerization, but almost no transport for stronger S(z) S(z) interaction, with a sharp crossover at J(z) =1 . Additionally, we perform a detailed analysis of the error made by the adaptive time-dependent DMRG using the fact that the evolution in the XX model is known exactly. We find that the error at small times is dominated by the error made by the Trotter decomposition, whereas for longer times the DMRG truncation error becomes the most important, with a very sharp crossover at some "runaway" time. Overall, errors are extremely small before the "runaway" time.
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real time Dynamics in spin 1 2 chains with adaptive time dependent density matrix renormalization group
Physical Review E, 2005Co-Authors: Dominique Gobert, Corinna Kollath, U Schollwock, Gunter M SchutzAbstract:We investigate the influence of different interaction strengths and dimerizations on the magnetization transport in antiferromagnetic spin $1∕2\phantom{\rule{0.3em}{0ex}}XXZ$ chains. We focus on the Real-Time evolution of the inhomogeneous initial state $\ensuremath{\mid}\ensuremath{\uparrow}\ensuremath{\cdots}\ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\cdots}\ensuremath{\downarrow}⟩$ in using the adaptive time-dependent density-matrix renormalization group (adaptive t-DMRG). Time scales accessible to us are of the order of 100 units of time measured in $\ensuremath{\hbar}∕J$ for almost negligible error in the observables. We find ballistic magnetization transport for small ${S}^{z}{S}^{z}$ interaction and arbitrary dimerization, but almost no transport for stronger ${S}^{z}{S}^{z}$ interaction, with a sharp crossover at ${J}^{z}=1$. Additionally, we perform a detailed analysis of the error made by the adaptive time-dependent DMRG using the fact that the evolution in the $XX$ model is known exactly. We find that the error at small times is dominated by the error made by the Trotter decomposition, whereas for longer times the DMRG truncation error becomes the most important, with a very sharp crossover at some ``runaway'' time. Overall, errors are extremely small before the ``runaway'' time.
Dominique Gobert - One of the best experts on this subject based on the ideXlab platform.
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real time Dynamics in spin 1 2 chains with adaptive time dependent density matrix renormalization group
Physical Review E, 2005Co-Authors: Dominique Gobert, Corinna Kollath, U Schollwock, Gunter M SchutzAbstract:: We investigate the influence of different interaction strengths and dimerizations on the magnetization transport in antiferromagnetic spin 1/2 XXZ chains. We focus on the Real-Time evolution of the inhomogeneous initial state |upward arrow... upward arrow downward arrow... downward arrow > in using the adaptive time-dependent density-matrix renormalization group (adaptive t-DMRG). Time scales accessible to us are of the order of 100 units of time measured in Planck's/J for almost negligible error in the observables. We find ballistic magnetization transport for small S(z) S(z) interaction and arbitrary dimerization, but almost no transport for stronger S(z) S(z) interaction, with a sharp crossover at J(z) =1 . Additionally, we perform a detailed analysis of the error made by the adaptive time-dependent DMRG using the fact that the evolution in the XX model is known exactly. We find that the error at small times is dominated by the error made by the Trotter decomposition, whereas for longer times the DMRG truncation error becomes the most important, with a very sharp crossover at some "runaway" time. Overall, errors are extremely small before the "runaway" time.
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real time Dynamics in spin 1 2 chains with adaptive time dependent density matrix renormalization group
Physical Review E, 2005Co-Authors: Dominique Gobert, Corinna Kollath, U Schollwock, Gunter M SchutzAbstract:We investigate the influence of different interaction strengths and dimerizations on the magnetization transport in antiferromagnetic spin $1∕2\phantom{\rule{0.3em}{0ex}}XXZ$ chains. We focus on the Real-Time evolution of the inhomogeneous initial state $\ensuremath{\mid}\ensuremath{\uparrow}\ensuremath{\cdots}\ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\cdots}\ensuremath{\downarrow}⟩$ in using the adaptive time-dependent density-matrix renormalization group (adaptive t-DMRG). Time scales accessible to us are of the order of 100 units of time measured in $\ensuremath{\hbar}∕J$ for almost negligible error in the observables. We find ballistic magnetization transport for small ${S}^{z}{S}^{z}$ interaction and arbitrary dimerization, but almost no transport for stronger ${S}^{z}{S}^{z}$ interaction, with a sharp crossover at ${J}^{z}=1$. Additionally, we perform a detailed analysis of the error made by the adaptive time-dependent DMRG using the fact that the evolution in the $XX$ model is known exactly. We find that the error at small times is dominated by the error made by the Trotter decomposition, whereas for longer times the DMRG truncation error becomes the most important, with a very sharp crossover at some ``runaway'' time. Overall, errors are extremely small before the ``runaway'' time.
Aurel Bulgac - One of the best experts on this subject based on the ideXlab platform.
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induced fission of 240 pu within a real time microscopic framework
Physical Review Letters, 2016Co-Authors: Aurel Bulgac, Piotr Magierski, Kenneth J Roche, I StetcuAbstract:We describe the fissioning Dynamics of ^{240}Pu from a configuration in the proximity of the outer fission barrier to full scission and the formation of the fragments within an implementation of density functional theory extended to superfluid systems and Real-Time Dynamics. The fission fragments emerge with properties similar to those determined experimentally, while the fission Dynamics appears to be quite complex, with many excited shape and pairing modes. The evolution is found to be much slower than previously expected, and the ultimate role of the collective inertia is found to be negligible in this fully nonadiabatic treatment of nuclear Dynamics, where all collective degrees of freedom (CDOF) are included (unlike adiabatic treatments with a small number of CDOF).
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time dependent density functional theory and the real time Dynamics of fermi superfluids
Annual Review of Nuclear and Particle Science, 2013Co-Authors: Aurel BulgacAbstract:I describe the time-dependent superfluid local density approximation, which is an adiabatic extension of the density functional theory to superfluid Fermi systems and their Real-Time Dynamics. This new theoretical framework has been used to describe several phenomena in cold atomic gases and nuclear collective motion: excitation of the Higgs modes in strongly interacting Fermi superfluids, generation of quantized vortices, crossing and reconnection of vortices, excitation of the superflow at velocities above the critical velocity, excitation of quantum shock waves and domain walls in the collisions of superfluid atomic clouds, and excitation of collective states in nuclei.
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strength of the vortex pinning interaction from real time Dynamics
Physical Review Letters, 2013Co-Authors: Aurel Bulgac, Michael Mcneil Forbes, Rishi SharmaAbstract:We present an efficient and general method to compute vortex-pinning interactions--which arise in neutron stars, superconductors, and trapped cold atoms--at arbitrary separations using Real-Time Dynamics. This method overcomes uncertainties associated with matter redistribution by the vortex position and the related choice of ensemble that plague the typical approach of comparing energy differences between stationary pinned and unpinned configurations: uncertainties that prevent agreement in the literature on the sign and magnitude of the vortex-nucleus interaction in the crust of neutron stars. We demonstrate and validate the method with Gross-Pitaevskii-like equations for the unitary Fermi gas, and demonstrate how the technique of adiabatic state preparation with time-dependent simulation can be used to calculate vortex-pinning interactions in fermionic systems such as the vortex-nucleus interaction in the crust of neutron stars.
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time dependent density functional theory and the real time Dynamics of fermi superfluids
arXiv: Quantum Gases, 2013Co-Authors: Aurel BulgacAbstract:I describe the Time-Dependent Superfluid Local Density Approximation, which is an adiabatic extension of the Density Functional Theory to superfluid Fermi systems and their Real-Time Dynamics. This new theoretical framework has been applied to describe a number of phenomena in cold atomic gases and nuclear collective motion: excitation of the Higgs modes in strongly interacting Fermi superfluids, generation of quantized vortices, crossing and reconnection of vortices, excitation of the superflow at velocities above the critical velocity, excitation of quantum shock waves and domain walls in the collisions of superfluid atomic clouds, excitation of collective states in nuclei.
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quantum shock waves and domain walls in the real time Dynamics of a superfluid unitary fermi gas
Physical Review Letters, 2012Co-Authors: Aurel Bulgac, Yuanlung Luo, Kenneth J RocheAbstract:We show that in the collision of two superfluid fermionic atomic clouds one observes the formation of quantum shock waves as discontinuities in the number density and collective flow velocity. Domain walls, which are topological excitations of the superfluid order parameter, are also generated and exhibit abrupt phase changes by π and slower motion than the shock waves. The domain walls are distinct from the gray soliton train or number density ripples formed in the wake of the shock waves and observed in the collisions of superfluid bosonic atomic clouds. Domain walls with opposite phase jumps appear to collide elastically.
Philipp Hauke - One of the best experts on this subject based on the ideXlab platform.
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real time Dynamics of lattice gauge theories with a few qubit quantum computer
Nature, 2016Co-Authors: Esteban Martinez, Christine A Muschik, Philipp Schindler, Daniel Nigg, Alexander Erhard, Markus Heyl, Philipp HaukeAbstract:A digital quantum simulation of a lattice gauge theory is performed on a quantum computer that consists of a few trapped-ion qubits; the model simulated is the Schwinger mechanism, which describes the creation of electron–positron pairs from vacuum. Quantum simulations promise to provide solutions to problems where classical computational methods fail. An example of a challenging computational problem is the Real-Time Dynamics in gauge theories — field theories paramount to modern particle physics. This paper presents a digital quantum simulation of a lattice gauge theory on a quantum computer consisting of a few qubits comprising trapped calcium controlled by electromagnetic fields. The specific model that the authors simulate is the Schwinger mechanism, which describes the creation of electron–positron pairs from vacuum. As an early example of a particle-physics theory simulated with an atomic physics experiment, this could potentially open the door to simulating more complicated and otherwise computationally intractable models. Gauge theories are fundamental to our understanding of interactions between the elementary constituents of matter as mediated by gauge bosons1,2. However, computing the Real-Time Dynamics in gauge theories is a notorious challenge for classical computational methods. This has recently stimulated theoretical effort, using Feynman’s idea of a quantum simulator3,4, to devise schemes for simulating such theories on engineered quantum-mechanical devices, with the difficulty that gauge invariance and the associated local conservation laws (Gauss laws) need to be implemented5,6,7. Here we report the experimental demonstration of a digital quantum simulation of a lattice gauge theory, by realizing (1 + 1)-dimensional quantum electroDynamics (the Schwinger model8,9) on a few-qubit trapped-ion quantum computer. We are interested in the Real-Time evolution of the Schwinger mechanism10,11, describing the instability of the bare vacuum due to quantum fluctuations, which manifests itself in the spontaneous creation of electron–positron pairs. To make efficient use of our quantum resources, we map the original problem to a spin model by eliminating the gauge fields12 in favour of exotic long-range interactions, which can be directly and efficiently implemented on an ion trap architecture13. We explore the Schwinger mechanism of particle–antiparticle generation by monitoring the mass production and the vacuum persistence amplitude. Moreover, we track the Real-Time evolution of entanglement in the system, which illustrates how particle creation and entanglement generation are directly related. Our work represents a first step towards quantum simulation of high-energy theories using atomic physics experiments—the long-term intention is to extend this approach to Real-Time quantum simulations of non-Abelian lattice gauge theories.
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analog quantum simulation of 1 1 dimensional lattice qed with trapped ions
Physical Review A, 2016Co-Authors: Philipp Hauke, P Zoller, Dayou Yang, G S Giri, M Johanning, Christof WunderlichAbstract:Experimentally feasible quantum simulation schemes are proposed to emulate a simple lattice gauge theory in trapped-ion chains, which may overcome the difficulty of simulating the relevant Real-Time Dynamics numerically.
U Schollwock - One of the best experts on this subject based on the ideXlab platform.
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real time Dynamics in spin 1 2 chains with adaptive time dependent density matrix renormalization group
Physical Review E, 2005Co-Authors: Dominique Gobert, Corinna Kollath, U Schollwock, Gunter M SchutzAbstract:: We investigate the influence of different interaction strengths and dimerizations on the magnetization transport in antiferromagnetic spin 1/2 XXZ chains. We focus on the Real-Time evolution of the inhomogeneous initial state |upward arrow... upward arrow downward arrow... downward arrow > in using the adaptive time-dependent density-matrix renormalization group (adaptive t-DMRG). Time scales accessible to us are of the order of 100 units of time measured in Planck's/J for almost negligible error in the observables. We find ballistic magnetization transport for small S(z) S(z) interaction and arbitrary dimerization, but almost no transport for stronger S(z) S(z) interaction, with a sharp crossover at J(z) =1 . Additionally, we perform a detailed analysis of the error made by the adaptive time-dependent DMRG using the fact that the evolution in the XX model is known exactly. We find that the error at small times is dominated by the error made by the Trotter decomposition, whereas for longer times the DMRG truncation error becomes the most important, with a very sharp crossover at some "runaway" time. Overall, errors are extremely small before the "runaway" time.
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real time Dynamics in spin 1 2 chains with adaptive time dependent density matrix renormalization group
Physical Review E, 2005Co-Authors: Dominique Gobert, Corinna Kollath, U Schollwock, Gunter M SchutzAbstract:We investigate the influence of different interaction strengths and dimerizations on the magnetization transport in antiferromagnetic spin $1∕2\phantom{\rule{0.3em}{0ex}}XXZ$ chains. We focus on the Real-Time evolution of the inhomogeneous initial state $\ensuremath{\mid}\ensuremath{\uparrow}\ensuremath{\cdots}\ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\cdots}\ensuremath{\downarrow}⟩$ in using the adaptive time-dependent density-matrix renormalization group (adaptive t-DMRG). Time scales accessible to us are of the order of 100 units of time measured in $\ensuremath{\hbar}∕J$ for almost negligible error in the observables. We find ballistic magnetization transport for small ${S}^{z}{S}^{z}$ interaction and arbitrary dimerization, but almost no transport for stronger ${S}^{z}{S}^{z}$ interaction, with a sharp crossover at ${J}^{z}=1$. Additionally, we perform a detailed analysis of the error made by the adaptive time-dependent DMRG using the fact that the evolution in the $XX$ model is known exactly. We find that the error at small times is dominated by the error made by the Trotter decomposition, whereas for longer times the DMRG truncation error becomes the most important, with a very sharp crossover at some ``runaway'' time. Overall, errors are extremely small before the ``runaway'' time.
