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1

Quantum many-body systems out of equilibrium

Closed quantum many-body systems out of equilibrium pose several long-standing problems in physics. Recent years have seen a tremendous progress in approaching these questions, not least due to experiments with cold atoms and trapped ions in instances of quantum simulations. This article provides an overview on the progress in understanding dynamical equilibration and thermalisation of closed quantum many-body systems out of equilibrium due to quenches, ramps and periodic driving. It also addresses topics such as the eigenstate thermalisation hypothesis, typicality, transport, many-body localisation, universality near phase transitions, and prospects for quantum simulations.

J. Eisert; M. Friesdorf; C. Gogolin

2014-08-21

2

Measure synchronization in quantum many-body systems

NASA Astrophysics Data System (ADS)

The concept of measure synchronization between two coupled quantum many-body systems is presented. In general terms we consider two quantum many-body systems whose dynamics gets coupled through the contact particle-particle interaction. This coupling is shown to produce measure synchronization, a generalization of synchrony to a large class of systems which takes place in absence of dissipation. We find that in quantum measure synchronization, the many-body quantum properties for the two subsystems, e.g., condensed fractions and particle fluctuations, behave in a coordinated way. To illustrate the concept we consider a simple case of two species of bosons occupying two distinct quantum states. Measure synchronization can be readily explored with state-of-the-art techniques in ultracold atomic gases and, if properly controlled, be employed to build targeted quantum correlations in a sympathetic way.

Qiu, Haibo; Juliá-Díaz, Bruno; Garcia-March, Miguel Angel; Polls, Artur

2014-09-01

3

Universal behavior beyond multifractality in quantum many-body systems.

How many states of a configuration space contribute to a wave function? Attempts to answer this ubiquitous question have a long history in physics and are keys to understanding, e.g., localization phenomena. Beyond single-particle physics, a quantitative study of the ground state complexity for interacting many-body quantum systems is notoriously difficult, mainly due to the exponential growth of the configuration (Hilbert) space with the number of particles. Here we develop quantum Monte Carlo schemes to overcome this issue, focusing on Shannon-Rényi entropies of ground states of large quantum many-body systems. Our simulations reveal a generic multifractal behavior while the very nature of quantum phases of matter and associated transitions is captured by universal subleading terms in these entropies. PMID:24580627

Luitz, David J; Alet, Fabien; Laflorencie, Nicolas

2014-02-01

4

Experimental quantum simulation of entanglement in many-body systems.

We employ a nuclear magnetic resonance (NMR) quantum information processor to simulate the ground state of an XXZ spin chain and measure its NMR analog of entanglement, or pseudoentanglement. The observed pseudoentanglement for a small-size system already displays a singularity, a signature which is qualitatively similar to that in the thermodynamical limit across quantum phase transitions, including an infinite-order critical point. The experimental results illustrate a successful approach to investigate quantum correlations in many-body systems using quantum simulators. PMID:21797528

Zhang, Jingfu; Wei, Tzu-Chieh; Laflamme, Raymond

2011-07-01

5

The Approach To Typicality in Many-Body Quantum Systems

NASA Astrophysics Data System (ADS)

The recent discovery that for large Hilbert spaces, almost all (that is, typical) Hamiltonians have eigenstates that place small subsystems in thermal equilibrium, has shed much light on the origins of irreversibility and thermalization. Here we present numerical evidence that many-body lattice systems generically approach typicality as the number of subsystems is increased, and thus provide further support for the eigenstate thermalization hypothesis. We will present our results that indicate that the deviation of many-body systems from typicality scales as an inverse power of the number of systems, and we compare this with the equivalent scaling for random Hamiltonians.

Vinjanampathy, Sai; Dubey, Shawn; Silvestri, Luciano; Jacobs, Kurt

2012-02-01

6

Nonlinear spectroscopy of controllable many-body quantum systems

NASA Astrophysics Data System (ADS)

We establish a novel approach to probing spatially resolved multitime correlation functions of interacting many-body systems, with scalable experimental overheads. Specifically, designing nonlinear measurement protocols for multidimensional spectra in a chain of trapped ions with single-site addressability enables us, for example, to distinguish coherent from incoherent transport processes, to quantify potential anharmonicities, and to identify decoherence-free subspaces.

Gessner, Manuel; Schlawin, Frank; Häffner, Hartmut; Mukamel, Shaul; Buchleitner, Andreas

2014-09-01

7

Approach to typicality in many-body quantum systems

NASA Astrophysics Data System (ADS)

The recent discovery that for large Hilbert spaces, almost all (that is, typical) Hamiltonians have eigenstates that place small subsystems in thermal equilibrium, has shed much light on the origins of irreversibility and thermalization. Here we give numerical evidence that many-body lattice systems generically approach typicality as the number of subsystems is increased, and thus provide further support for the eigenstate thermalization hypothesis. Our results indicate that the deviation of many-body systems from typicality decreases exponentially with the number of systems. Further, by averaging over a number of randomly selected nearest-neighbor interactions, we obtain a powerlaw for the atypicality as a function of the Hilbert space dimension, distinct from the power law possessed by random Hamiltonians.

Dubey, Shawn; Silvestri, Luciano; Finn, Justin; Vinjanampathy, Sai; Jacobs, Kurt

2012-01-01

8

The approach to typicality in many-body quantum systems

The recent discovery that for large Hilbert spaces, almost all (that is, typical) Hamiltonians have eigenstates that place small subsystems in thermal equilibrium, has shed much light on the origins of irreversibility and thermalization. Here we give numerical evidence that many-body lattice systems generically approach typicality as the number of subsystems is increased, and thus provide further support for the eigenstate thermalization hypothesis. Our results indicate that the deviation of many-body systems from typicality decreases exponentially with the number of systems. Further, by averaging over a number of randomly-selected nearest-neighbor interactions, we obtain a power-law for the atypicality as a function of the Hilbert space dimension, distinct from the power-law possessed by random Hamiltonians.

Shawn Dubey; Luciano Silvestri; Justin Finn; Sai Vinjanampathy; Kurt Jacobs

2011-12-15

9

Characterizing and Quantifying Frustration in Quantum Many-Body Systems

We present a general scheme for the study of frustration in quantum systems. We introduce a universal measure of frustration for arbitrary quantum systems and we relate it to a class of entanglement monotones via an exact inequality. If all the (pure) ground states of a given Hamiltonian saturate the inequality, then the system is said to be inequality saturating. We introduce sufficient conditions for a quantum spin system to be inequality saturating and confirm them with extensive numerical tests. These conditions provide a generalization to the quantum domain of the Toulouse criteria for classical frustration-free systems. The models satisfying these conditions can be reasonably identified as geometrically unfrustrated and subject to frustration of purely quantum origin. Our results therefore establish a unified framework for studying the intertwining of geometric and quantum contributions to frustration.

S. M. Giampaolo; G. Gualdi; A. Monras; F. Illuminati

2011-02-28

10

General coordinate invariance in quantum many-body systems

We extend the notion of general coordinate invariance to many-body, not necessarily relativistic, systems. As an application, we investigate nonrelativistic general covariance in Galilei-invariant systems. The peculiar transformation rules for the background metric and gauge fields, first introduced by Son and Wingate in 2005 and refined in subsequent works, follow naturally from our framework. Our approach makes it clear that Galilei or Poincare symmetry is by no means a necessary prerequisite for making the theory invariant under coordinate diffeomorphisms. General covariance merely expresses the freedom to choose spacetime coordinates at will, whereas the true, physical symmetries of the system can be separately implemented as "internal" symmetries within the vielbein formalism. A systematic way to implement such symmetries is provided by the coset construction. We illustrate this point by applying our formalism to nonrelativistic s-wave superfluids.

Tomas Brauner; Solomon Endlich; Alexander Monin; Riccardo Penco

2014-07-29

11

Relaxation and Thermalization of Isolated Many-Body Quantum Systems

We provide an overview of our numerical and analytical studies of isolated interacting quantum systems that are taken out of equilibrium instantaneously (quenched). We describe the relaxation process to a new equilibrium and obtain lower bounds for the relaxation time of full random matrices and realistic systems with two-body interactions. We show that the size of the time fluctuations after relaxation decays exponentially with system size for systems without too many degeneracies. We also discuss the conditions for thermalization and demonstrate that it can happen after local and global quenches in space. The analyses are developed for systems, initial states, and few-body observables accessible to experiments with optical lattices.

E. J. Torres-Herrera; Davida Kollmar; Lea F. Santos

2014-03-25

12

Localization and Glassy Dynamics Of Many-Body Quantum Systems

When classical systems fail to explore their entire configurational space, intriguing macroscopic phenomena like aging and glass formation may emerge. Also closed quanto-mechanical systems may stop wandering freely around the whole Hilbert space, even if they are initially prepared into a macroscopically large combination of eigenstates. Here, we report numerical evidences that the dynamics of strongly interacting lattice bosons driven sufficiently far from equilibrium can be trapped into extremely long-lived inhomogeneous metastable states. The slowing down of incoherent density excitations above a threshold energy, much reminiscent of a dynamical arrest on the verge of a glass transition, is identified as the key feature of this phenomenon. We argue that the resulting long-lived inhomogeneities are responsible for the lack of thermalization observed in large systems. Such a rich phenomenology could be experimentally uncovered upon probing the out-of-equilibrium dynamics of conveniently prepared quantum states of trapped cold atoms which we hereby suggest. PMID:22355756

Carleo, Giuseppe; Becca, Federico; Schiro, Marco; Fabrizio, Michele

2012-01-01

13

Numerical simulation of quantum many-body systems

Results for the single-particle density of states and the conductivity were obtained for both the attractive-and repulsive-U Hubbard models. At half-filling the densities of states for both models are identical, but the gap for the attractive case arises from the formation of charge-density-wave and superconducting correlations, while for the repulsive-U Hubbard model the gap is the Mott-Hubbard gap and arises from the antiferromagnetic, Coulomb, correlations. Hubbard chains were studied by use of a generalization of Handscomb's quantum Monte Carlo scheme. Monte Carlo calculations of the two-particle vertex of the 2D repulsive-U Hubbard model were carried out. Criteria for determining whether a system is insulating, metallic, or superconducting were investigated; it was found for lattice models (Hubbard, Holstein, etc.) that this is determined by the value of the current- function.

Scalapino, D.J.

1992-01-01

14

Numerical simulation of quantum many-body systems

Results for the single-particle density of states and the conductivity were obtained for both the attractive-and repulsive-U Hubbard models. At half-filling the densities of states for both models are identical, but the gap for the attractive case arises from the formation of charge-density-wave and superconducting correlations, while for the repulsive-U Hubbard model the gap is the Mott-Hubbard gap and arises from the antiferromagnetic, Coulomb, correlations. Hubbard chains were studied by use of a generalization of Handscomb`s quantum Monte Carlo scheme. Monte Carlo calculations of the two-particle vertex of the 2D repulsive-U Hubbard model were carried out. Criteria for determining whether a system is insulating, metallic, or superconducting were investigated; it was found for lattice models (Hubbard, Holstein, etc.) that this is determined by the value of the current- function.

Scalapino, D.J.

1992-12-31

15

Preparing ground states of quantum many-body systems on a quantum computer

NASA Astrophysics Data System (ADS)

The simulation of quantum many-body systems is a notoriously hard problem in condensed matter physics, but it could easily be handled by a quantum computer [4,1]. There is however one catch: while a quantum computer can naturally implement the dynamics of a quantum system --- i.e. solve Schr"odinger's equation --- there was until now no general method to initialize the computer in a low-energy state of the simulated system. We present a quantum algorithm [5] that can prepare the ground state and thermal states of a quantum many-body system in a time proportional to the square-root of its Hilbert space dimension. This is the same scaling as required by the best known algorithm to prepare the ground state of a classical many-body system on a quantum computer [3,2]. This provides strong evidence that for a quantum computer, preparing the ground state of a quantum system is in the worst case no more difficult than preparing the ground state of a classical system. 1 D. Aharonov and A. Ta-Shma, Adiabatic quantum state generation and statistical zero knowledge, Proc. 35th Annual ACM Symp. on Theo. Comp., (2003), p. 20. F. Barahona, On the computational complexity of ising spin glass models, J. Phys. A. Math. Gen., 15 (1982), p. 3241. C. H. Bennett, E. Bernstein, G. Brassard, and U. Vazirani, Strengths and weaknessess of quantum computing, SIAM J. Comput., 26 (1997), pp. 1510--1523, quant-ph/9701001. S. Lloyd, Universal quantum simulators, Science, 273 (1996), pp. 1073--1078. D. Poulin and P. Wocjan, Preparing ground states of quantum many-body systems on a quantum computer, 2008, arXiv:0809.2705.

Poulin, David

2009-03-01

16

Quantum Phase Space, Quantization Hierarchy, and Eclectic Quantum Many-Body System

An operator-valued quantum phase space formula is constructed. The phase space formula of Quantum Mechanics provides a natural link between first and second quantization, thus contributing to the understanding of quantization problem. By the combination of quantization and hamiltonization of dynamics, a quantization hierarchy is introduced, beyond the framework of first and second quantization and generalizing the standard quantum theory. We apply our quantization method to quantum many-body system and propose an eclectic model, in which the dimension of Hilbert space does not scale exponentially with the number of particles due to the locality of interaction, and the evolution is a constrained Hamiltonian dynamics.

Dong-Sheng Wang

2014-10-05

17

Observation of entanglement propagation in a quantum many-body system

The key to explaining a wide range of quantum phenomena is understanding how entanglement propagates around many-body systems. Furthermore, the controlled distribution of entanglement is of fundamental importance for quantum communication and computation. In many situations, quasiparticles are the carriers of information around a quantum system and are expected to distribute entanglement in a fashion determined by the system interactions. Here we report on the observation of magnon quasiparticle dynamics in a one-dimensional many-body quantum system of trapped ions representing an Ising spin model. Using the ability to tune the effective interaction range, and to prepare and measure the quantum state at the individual particle level, we observe new quasiparticle phenomena. For the first time, we reveal the entanglement distributed by quasiparticles around a many-body system. Second, for long-range interactions we observe the divergence of quasiparticle velocity and breakdown of the light-cone picture that is ...

Jurcevic, P; Hauke, P; Hempel, C; Zoller, P; Blatt, R; Roos, C F

2014-01-01

18

Quantum simulation. Coherent imaging spectroscopy of a quantum many-body spin system.

Quantum simulators, in which well-controlled quantum systems are used to reproduce the dynamics of less understood ones, have the potential to explore physics inaccessible to modeling with classical computers. However, checking the results of such simulations also becomes classically intractable as system sizes increase. Here, we introduce and implement a coherent imaging spectroscopic technique, akin to magnetic resonance imaging, to validate a quantum simulation. We use this method to determine the energy levels and interaction strengths of a fully connected quantum many-body system. Additionally, we directly measure the critical energy gap near a quantum phase transition. We expect this general technique to become a verification tool for quantum simulators once experiments advance beyond proof-of-principle demonstrations and exceed the resources of conventional computers. PMID:25061207

Senko, C; Smith, J; Richerme, P; Lee, A; Campbell, W C; Monroe, C

2014-07-25

19

Self-consistent projection operator theory for quantum many-body systems

NASA Astrophysics Data System (ADS)

We derive an exact equation of motion for the reduced density matrices of individual subsystems of quantum many-body systems of any lattice dimension and arbitrary system size. Our projection operator based theory yields a highly efficient analytical and numerical approach. Besides its practical use it provides an interpretation and systematic extension of mean-field approaches and an adaption of open quantum systems theory to settings where a dynamically evolving environment has to be taken into account. We show its high accuracy for two significant classes of complex quantum many-body dynamics, unitary evolutions of nonequilibrium states in closed and stationary states in driven-dissipative systems.

Degenfeld-Schonburg, Peter; Hartmann, Michael J.

2014-06-01

20

Density matrix renormalization group approach for many-body open quantum systems

The density matrix renormalization group (DMRG) approach is extended to complex-symmetric density matrices characteristic of many-body open quantum systems. Within the continuum shell model, we investigate the interplay between many-body configuration interaction and coupling to open channels. It is shown that the DMRG technique applied to broad resonances in the unbound neutron-rich nucleus 7He provides a highly accurate treatment of the coupling to the non-resonant scattering continuum.

J. Rotureau; N. Michel; W. Nazarewicz; M. Ploszajczak; J. Dukelsky

2006-03-07

21

Light-cone-like spreading of correlations in a quantum many-body system.

In relativistic quantum field theory, information propagation is bounded by the speed of light. No such limit exists in the non-relativistic case, although in real physical systems, short-range interactions may be expected to restrict the propagation of information to finite velocities. The question of how fast correlations can spread in quantum many-body systems has been long studied. The existence of a maximal velocity, known as the Lieb-Robinson bound, has been shown theoretically to exist in several interacting many-body systems (for example, spins on a lattice)--such systems can be regarded as exhibiting an effective light cone that bounds the propagation speed of correlations. The existence of such a 'speed of light' has profound implications for condensed matter physics and quantum information, but has not been observed experimentally. Here we report the time-resolved detection of propagating correlations in an interacting quantum many-body system. By quenching a one-dimensional quantum gas in an optical lattice, we reveal how quasiparticle pairs transport correlations with a finite velocity across the system, resulting in an effective light cone for the quantum dynamics. Our results open perspectives for understanding the relaxation of closed quantum systems far from equilibrium, and for engineering the efficient quantum channels necessary for fast quantum computations. PMID:22281597

Cheneau, Marc; Barmettler, Peter; Poletti, Dario; Endres, Manuel; Schauss, Peter; Fukuhara, Takeshi; Gross, Christian; Bloch, Immanuel; Kollath, Corinna; Kuhr, Stefan

2012-01-26

22

Diffusion Monte Carlo: A powerful tool for studying quantum many-body systems

NASA Astrophysics Data System (ADS)

Diffusion quantum Monte Carlo is introduced at an elementary level. We highlight the strengths of the method in addressing important issues associated with quantum many-body systems, such as those associated with the ground-state energy and pair-distribution function. 4He clusters trapped on a graphite surface are simulated as an example of the method. A sample program and documentation for developing simulation projects are provided.

Pang, Tao

2014-10-01

23

Coherent Imaging Spectroscopy of a Quantum Many-Body Spin System

Quantum simulators, in which well controlled quantum systems are used to reproduce the dynamics of less understood ones, have the potential to explore physics that is inaccessible to modeling with classical computers. However, checking the results of such simulations will also become classically intractable as system sizes increase. In this work, we introduce and implement a coherent imaging spectroscopic technique to validate a quantum simulation, much as magnetic resonance imaging exposes structure in condensed matter. We use this method to determine the energy levels and interaction strengths of a fully-connected quantum many-body system. Additionally, we directly measure the size of the critical energy gap near a quantum phase transition. We expect this general technique to become an important verification tool for quantum simulators once experiments advance beyond proof-of-principle demonstrations and exceed the resources of conventional computers.

C. Senko; J. Smith; P. Richerme; A. Lee; W. C. Campbell; C. Monroe

2014-01-22

24

Quasiparticle engineering and entanglement propagation in a quantum many-body system.

The key to explaining and controlling a range of quantum phenomena is to study how information propagates around many-body systems. Quantum dynamics can be described by particle-like carriers of information that emerge in the collective behaviour of the underlying system, the so-called quasiparticles. These elementary excitations are predicted to distribute quantum information in a fashion determined by the system's interactions. Here we report quasiparticle dynamics observed in a quantum many-body system of trapped atomic ions. First, we observe the entanglement distributed by quasiparticles as they trace out light-cone-like wavefronts. Second, using the ability to tune the interaction range in our system, we observe information propagation in an experimental regime where the effective-light-cone picture does not apply. Our results will enable experimental studies of a range of quantum phenomena, including transport, thermalization, localization and entanglement growth, and represent a first step towards a new quantum-optic regime of engineered quasiparticles with tunable nonlinear interactions. PMID:25008526

Jurcevic, P; Lanyon, B P; Hauke, P; Hempel, C; Zoller, P; Blatt, R; Roos, C F

2014-07-10

25

Quasiparticle engineering and entanglement propagation in a quantum many-body system

NASA Astrophysics Data System (ADS)

The key to explaining and controlling a range of quantum phenomena is to study how information propagates around many-body systems. Quantum dynamics can be described by particle-like carriers of information that emerge in the collective behaviour of the underlying system, the so-called quasiparticles. These elementary excitations are predicted to distribute quantum information in a fashion determined by the system's interactions. Here we report quasiparticle dynamics observed in a quantum many-body system of trapped atomic ions. First, we observe the entanglement distributed by quasiparticles as they trace out light-cone-like wavefronts. Second, using the ability to tune the interaction range in our system, we observe information propagation in an experimental regime where the effective-light-cone picture does not apply. Our results will enable experimental studies of a range of quantum phenomena, including transport, thermalization, localization and entanglement growth, and represent a first step towards a new quantum-optic regime of engineered quasiparticles with tunable nonlinear interactions.

Jurcevic, P.; Lanyon, B. P.; Hauke, P.; Hempel, C.; Zoller, P.; Blatt, R.; Roos, C. F.

2014-07-01

26

Real-space decoupling transformation for quantum many-body systems.

We propose a real-space renormalization group method to explicitly decouple into independent components a many-body system that, as in the phenomenon of spin-charge separation, exhibits separation of degrees of freedom at low energies. Our approach produces a branching holographic description of such systems that opens the path to the efficient simulation of the most entangled phases of quantum matter, such as those whose ground state violates a boundary law for entanglement entropy. As in the coarse-graining transformation of Vidal [Phys. Rev. Lett. 99, 220405 (2007). PMID:24949747

Evenbly, G; Vidal, G

2014-06-01

27

Seniority in quantum many-body systems. I. Identical particles in a single shell

NASA Astrophysics Data System (ADS)

A discussion of the seniority quantum number in many-body systems is presented. The analysis is carried out for bosons and fermions simultaneously but is restricted to identical particles occupying a single shell. The emphasis of the paper is on the possibility of partial conservation of seniority which turns out to be a peculiar property of spin-9/2 fermions but prevalent in systems of interacting bosons of any spin. Partial conservation of seniority is at the basis of the existence of seniority isomers, frequently observed in semi-magic nuclei, and also gives rise to peculiar selection rules in one-nucleon transfer reactions.

Van Isacker, P.; Heinze, S.

2014-10-01

28

NASA Astrophysics Data System (ADS)

We analyze the nature of the statistics of the work done on or by a quantum many-body system brought out of equilibrium. We show that, for the sudden quench and for an initial state that commutes with the initial Hamiltonian, it is possible to retrieve the whole nonequilibrium thermodynamics via single projective measurements of observables. We highlight, in a physically clear way, the qualitative implications for the statistics of work coming from considering processes described by operators that either commute or do not commute with the unperturbed Hamiltonian of a given system. We consider a quantum many-body system and derive an expression that allows us to give a physical interpretation, for a thermal initial state, to all of the cumulants of the work in the case of quenched operators commuting with the unperturbed Hamiltonian. In the commuting case, the observables that we need to measure have an intuitive physical meaning. Conversely, in the noncommuting case, we show that, although it is possible to operate fully within the single-measurement framework irrespectively of the size of the quench, some difficulties are faced in providing a clear-cut physical interpretation to the cumulants. This circumstance makes the study of the physics of the system nontrivial and highlights the nonintuitive phenomenology of the emergence of thermodynamics from the fully quantum microscopic description. We illustrate our ideas with the example of the Ising model in a transverse field showing the interesting behavior of the high-order statistical moments of the work distribution for a generic thermal state and linking them to the critical nature of the model itself.

Fusco, L.; Pigeon, S.; Apollaro, T. J. G.; Xuereb, A.; Mazzola, L.; Campisi, M.; Ferraro, A.; Paternostro, M.; De Chiara, G.

2014-07-01

29

Theory of classical and quantum frustration in quantum many-body systems

We present a general scheme for the study of frustration in quantum systems. After introducing a universal measure of frustration for arbitrary quantum systems, we derive for it an exact inequality in terms of a class of entanglement monotones. We then state sufficient conditions for the ground states of quantum spin systems to saturate the inequality and confirm them with extensive numerical tests. These conditions provide a generalization to the quantum domain of the Toulouse criteria for classical frustration-free systems and establish a unified framework for studying the intertwining of geometric and quantum contributions to frustration.

Giampaolo, S M; Monras, A; Illuminati, F

2011-01-01

30

Particle entanglement in continuum many-body systems via quantum Monte Carlo

NASA Astrophysics Data System (ADS)

Entanglement of spatial bipartitions, used to explore lattice models in condensed matter physics, may be insufficient to fully describe itinerant quantum many-body systems in the continuum. We introduce a procedure to measure the Rényi entanglement entropies on a particle bipartition, with general applicability to continuum Hamiltonians via path integral Monte Carlo methods. Via direct simulations of interacting bosons in one spatial dimension, we confirm a logarithmic scaling of the single-particle entanglement entropy with the number of particles in the system. The coefficient of this logarithmic scaling increases with interaction strength, saturating to unity in the strongly interacting limit. Additionally, we show that the single-particle entanglement entropy is bounded by the condensate fraction, suggesting a practical route towards its measurement in future experiments.

Herdman, C. M.; Roy, P.-N.; Melko, R. G.; Del Maestro, A.

2014-04-01

31

Lattice mapping for many-body open quantum systems and its application to atoms in photonic crystals

NASA Astrophysics Data System (ADS)

We present a derivation that maps the original problem of a many-body open quantum system (OQS) coupled to a harmonic oscillator reservoir into that of a many-body OQS coupled to a lattice of harmonic oscillators. The present method is particularly suitable to analyze the dynamics of atoms arranged in a periodic structure and coupled with the electromagnetic field within a photonic crystal. It allows to solve the dynamics of a many-body OQS with methods alternative to the commonly used master, stochastic Schrödinger, and Heisenberg equations, and thus to reach regimes well beyond the weak coupling and Born-Markov approximations.

de Vega, Inés

2014-10-01

32

Quantum Information Processing with Quantum Zeno Many-Body Dynamics

We show how the quantum Zeno effect can be exploited to control quantum many-body dynamics for quantum information and computation purposes. In particular, we consider a one dimensional array of three level systems interacting via a nearest-neighbour interaction. By encoding the qubit on two levels and using simple projective frequent measurements yielding the quantum Zeno effect, we demonstrate how to

Alex Monras; Oriol Romero-Isart

2008-01-01

33

Quantum phases and transitions of many-body systems realized using cold atomic gases

NASA Astrophysics Data System (ADS)

In recent years, new advances in techniques for trapping and cooling atoms have allowed the production of atomic gases at low-enough temperatures and high-enough densities for collective quantum-mechanical effects to become important. This thesis describes theoretical investigations of certain many-body physics problems motivated by these experimental developments. It consists of two main parts. In the first, I investigate the array of phases exhibited by degenerate mixtures of bosons and fermions with a Feshbach resonance, a bound molecular state whose energy can be tuned with a magnetic field. These phases are distinguished by the presence or absence of a bosonic condensate and also by the different Luttinger constraints that are shown to apply to the Fermi surface(s). The second part is concerned with bosons in an optical lattice, in which a periodic potential is produced by counterpropagating lasers. Spinless bosons are known to exhibit a quantum phase transition between a Mott insulator and a superfluid state, while bosons with spin have a much richer phase structure. I consider, in particular, a phase transition with a spinless order parameter, and show that the long-time dynamics of spin-carrying excitations is governed by a nontrivial fixed point. The corresponding anomalous exponents are found using a renormalization-group calculation.

Powell, Stephen Christopher

34

Eigenvalues and low energy eigenvectors of quantum many-body systems

I first give an overview of the thesis and Matrix Product States (MPS) representation of quantum spin systems on a line with an improvement on the notation. The rest of this thesis is divided into two parts. The first part ...

Movassagh, Ramis

2012-01-01

35

NASA Astrophysics Data System (ADS)

We explore the relaxation dynamics of quantum many-body systems that undergo purely dissipative dynamics through non-classical jump operators that can establish quantum coherence. Our goal is to shed light on the differences in the relaxation dynamics that arise in comparison to systems evolving via classical rate equations. In particular, we focus on a scenario where both quantum and classical dissipative evolution lead to a stationary state with the same values of diagonal or "classical" observables. As a basis for illustrating our ideas we use spin systems whose dynamics becomes correlated and complex due to dynamical constraints, inspired by kinetically constrained models (KCMs) of classical glasses. We show that in the quantum case the relaxation can be orders of magnitude slower than the classical one due to the presence of quantum coherences. Aspects of these idealized quantum KCMs become manifest in a strongly interacting Rydberg gas under electromagnetically induced transparency (EIT) conditions in an appropriate limit. Beyond revealing a link between this Rydberg gas and the rather abstract dissipative KCMs of quantum glassy systems, our study sheds light on the limitations of the use of classical rate equations for capturing the non-equilibrium behavior of this many-body system.

Olmos, Beatriz; Lesanovsky, Igor; Garrahan, Juan P.

2014-10-01

36

Many-body entanglement in gapped quantum systems : representation, classification, and application

Entanglement is a special form of quantum correlation that exists among quantum particles and it has been realized that surprising things can happen when a large number of particles are entangled together. For example, ...

Chen, Xie, Ph. D. Massachusetts Institute of Technology

2012-01-01

37

NASA Astrophysics Data System (ADS)

Systems that involve N identical, interacting particles under quantum confinement appear throughout many areas of physics, including chemical, condensed matter, and atomic physics. In this thesis, we present the methods of dimensional perturbation theory, a powerful set of tools that uses symmetry to yield simple results for studying such many-body systems. We present a detailed discussion of the dimensional continuation of the N-particle Schrodinger equation, the D ? infinity equilibrium structure, and the normal-mode oscillations of this structure. We use the Wilson FG matrix method to derive general, analytical expressions for the many-body normal-mode vibrational frequencies, and we give analytical results for three N-body quantum-confined systems: the N-electron atom, N-electron quantum dot, and N-atom inhomogeneous Bose-Einstein condensate with a repulsive hard-core potential. The focus of this thesis will be on the many-body physics of Bose-Einstein condensates (BEC). The achievement of BEC in magnetically trapped alkali-metal atoms in 1995 has generated a considerable amount of experimental and theoretical activity in recent years. In typical BEC experiments, the average distance between the bose atoms is much larger than the range of the atomic interactions, and hence, the properties of these weakly interacting condensates have been successfully described by the mean-field nonlinear Gross-Pitaevskii equation. Recently, however, no longer restricted to the atom's natural interaction parameter, experimentalists have created condensates with a "knob" (i.e., a Feshbach resonance) that allows them to adjust the interaction to whatever strength, repulsive or attractive, they wish. These strongly interacting condensates provide a new test bed for fundamental atomic and many-body physics. In this thesis we develop a theory that goes beyond the standard mean-field approximation for many-body systems. Feshbach resonances notwithstanding, most experimentally realized atomic-vapor condensates are dilute and are best described by the mean-field Gross-Pitaevskii equation. For this reason, we use dimensional scaling methods to obtain an analytical approximation to the GP equation that is more accurate and flexible than the commonly used ground-state Thomas-Fermi approximation. We also demonstrate the power of dimensional perturbation theory by providing a full solution of a model BEC Hamiltonian and a two-electron quantum dot Hamiltonian. A feature shared by these examples is the high degree of accuracy provided by the lowest orders of the perturbation theory. In our approach to the full many-body BEC Hamiltonian, we use the lowest orders of many-body dimensional perturbation theory to obtain semi-analytical ground-state energies and collective excitation frequencies. Our many-body calculations for BEC's compare well with the Gross-Pitaevskii results in the weakly-interacting regime, as they should, and are much improved over mean-field theory predictions in the strongly-interacting regime.

McKinney, Brett Allen

38

Complexity of controlling quantum many-body dynamics

We demonstrate that arbitrary time evolutions of many-body quantum systems can be reversed even in cases when only part of the Hamiltonian can be controlled. The reversed dynamics obtained via optimal control—contrary to ...

Caneva, T.

39

Topological interactions of Nambu-Goldstone bosons in quantum many-body systems

We classify effective actions for Nambu-Goldstone (NG) bosons assuming absence of quantum anomalies. Lagrangians invariant only up to a surface term can be mapped to Chern-Simons (CS) theories for unbroken symmetry. Without making specific assumptions on spacetime symmetry, we give explicit expressions for these Lagrangians, generalizing the Berry and Hopf terms in ferromagnets. The order-three CS term exhibits a novel type of interaction among NG bosons. We discuss physical consequences of this term, working out in particular its realization for the quantum Hall ferromagnet phase of graphene.

Brauner, Tomas

2014-01-01

40

Two-time correlations are a crucial tool to probe the dynamics of many-body systems. We use these correlation functions to study the dynamics of dissipative quantum systems. Extending the adiabatic elimination method, we show that the correlations can display two distinct behaviors, depending on the observable of interest: a fast exponential decay, with a timescale of the order of the dissipative coupling, or a much slower dynamics. We apply this formalism to bosons in a double well subjected to phase noise. While the single-particle correlations decay exponentially, the density-density correlations display slow aging dynamics. We also show that the two-time correlations of dissipatively engineered quantum states can evolve in a drastically different manner compared to their Hamiltonian counterparts.

Bruno Sciolla; Dario Poletti; Corinna Kollath

2014-07-18

41

We have experimentally tested a recently suggested possibility for anomalous sensitivity of the cross sections of dissipative heavy ion collisions. Cross sections for the $^{19}$F+$^{27}$Al dissipative collisions were measured at the fixed energy 118.75 MeV of the $^{19}$F for the 12 different beam spots on the same target foil. The data demonstrate dramatic differences between the cross sections for the different beam spots. The effect may indicate deterministic randomness in complex quantum collisions. New experiments are highly desirable in a view of the fundamental importance of the problem.

Qi Wang; Jian-Long Han; Yu-Chuan Dong; Song-Lin Li; Li-Min Duan; Hu-Shan Xu; Hua-Gen Xu; Ruo-Fu Chen; He-Yu Wu; Zhen Bai; Zhi-Chang Li; Xiu-Qin Lu; Kui Zhao; Jian-Cheng Liu; Guo-Ji Xu; S. Yu. Kun

2007-05-31

42

Tensor Renormalization of Quantum Many-Body Systems Using Projected Entangled Simplex States

NASA Astrophysics Data System (ADS)

We propose a new class of tensor-network states, which we name projected entangled simplex states (PESS), for studying the ground-state properties of quantum lattice models. These states extend the pair-correlation basis of projected entangled pair states to a simplex. PESS are exact representations of the simplex solid states, and they provide an efficient trial wave function that satisfies the area law of entanglement entropy. We introduce a simple update method for evaluating the PESS wave function based on imaginary-time evolution and the higher-order singular-value decomposition of tensors. By applying this method to the spin-1/2 antiferromagnetic Heisenberg model on the kagome lattice, we obtain accurate and systematic results for the ground-state energy, which approach the lowest upper bounds yet estimated for this quantity.

Xie, Z. Y.; Chen, J.; Yu, J. F.; Kong, X.; Normand, B.; Xiang, T.

2014-01-01

43

Many-Body Localization in a Disordered Quantum Ising Chain

NASA Astrophysics Data System (ADS)

Many-body localization occurs in isolated quantum systems when Anderson localization persists in the presence of finite interactions. Despite strong evidence for the existence of a many-body localization transition, a reliable extraction of the critical disorder strength is difficult due to a large drift with system size in the studied quantities. In this Letter, we explore two entanglement properties that are promising for the study of the many-body localization transition: the variance of the half-chain entanglement entropy of exact eigenstates and the long time change in entanglement after a local quench from an exact eigenstate. We investigate these quantities in a disordered quantum Ising chain and use them to estimate the critical disorder strength and its energy dependence. In addition, we analyze a spin-glass transition at large disorder strength and provide evidence for it being a separate transition. We, thereby, give numerical support for a recently proposed phase diagram of many-body localization with localization protected quantum order [Huse et al., Phys. Rev. B 88, 014206 (2013)].

Kjäll, Jonas A.; Bardarson, Jens H.; Pollmann, Frank

2014-09-01

44

Many-body localization in a disordered quantum Ising chain.

Many-body localization occurs in isolated quantum systems when Anderson localization persists in the presence of finite interactions. Despite strong evidence for the existence of a many-body localization transition, a reliable extraction of the critical disorder strength is difficult due to a large drift with system size in the studied quantities. In this Letter, we explore two entanglement properties that are promising for the study of the many-body localization transition: the variance of the half-chain entanglement entropy of exact eigenstates and the long time change in entanglement after a local quench from an exact eigenstate. We investigate these quantities in a disordered quantum Ising chain and use them to estimate the critical disorder strength and its energy dependence. In addition, we analyze a spin-glass transition at large disorder strength and provide evidence for it being a separate transition. We, thereby, give numerical support for a recently proposed phase diagram of many-body localization with localization protected quantum order [Huse et al., Phys. Rev. B 88, 014206 (2013). PMID:25238383

Kjäll, Jonas A; Bardarson, Jens H; Pollmann, Frank

2014-09-01

45

We study coherent superpositions of clockwise and anticlockwise rotating intermediate complexes with overlapping resonances formed in bimolecular chemical reactions. Disintegration of such complexes represents an analog of a famous double-slit experiment. The time for disappearance of the interference fringes is estimated from heuristic arguments related to fingerprints of chaotic dynamics of a classical counterpart of the coherently rotating complex. Validity of this estimate is confirmed numerically for the H+D{sub 2} chemical reaction. Thus we demonstrate the quantum-classical transition in temporal behavior of highly excited quantum many-body systems in the absence of external noise and coupling to an environment.

Benet, L. [Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico (UNAM), 62210-Cuernavaca, Morelos (Mexico); Chadderton, L. T. [Atomic and Molecular Physics Laboratary, RSPhysSE, Australian National University, Canberra ACT 0200 (Australia); Kun, S. Yu. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos (UAEM), 62209-Cuernavaca, Morelos (Mexico); Nonlinear Physics Center and Department of Theoretical Physics, RSPhysSE, Australian National University, Canberra ACT 0200 (Australia); Qi Wang [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2007-06-15

46

EDITORIAL: Focus on Quantum Information and Many-Body Theory

NASA Astrophysics Data System (ADS)

Quantum many-body models describing natural systems or materials and physical systems assembled piece by piece in the laboratory for the purpose of realizing quantum information processing share an important feature: intricate correlations that originate from the coherent interaction between a large number of constituents. In recent years it has become manifest that the cross-fertilization between research devoted to quantum information science and to quantum many-body physics leads to new ideas, methods, tools, and insights in both fields. Issues of criticality, quantum phase transitions, quantum order and magnetism that play a role in one field find relations to the classical simulation of quantum systems, to error correction and fault tolerance thresholds, to channel capacities and to topological quantum computation, to name but a few. The structural similarities of typical problems in both fields and the potential for pooling of ideas then become manifest. Notably, methods and ideas from quantum information have provided fresh approaches to long-standing problems in strongly correlated systems in the condensed matter context, including both numerical methods and conceptual insights. Focus on quantum information and many-body theory Contents TENSOR NETWORKS Homogeneous multiscale entanglement renormalization ansatz tensor networks for quantum critical systems M Rizzi, S Montangero, P Silvi, V Giovannetti and Rosario Fazio Concatenated tensor network states R Hübener, V Nebendahl and W Dür Entanglement renormalization in free bosonic systems: real-space versus momentum-space renormalization group transforms G Evenbly and G Vidal Finite-size geometric entanglement from tensor network algorithms Qian-Qian Shi, Román Orús, John Ove Fjærestad and Huan-Qiang Zhou Characterizing symmetries in a projected entangled pair state D Pérez-García, M Sanz, C E González-Guillén, M M Wolf and J I Cirac Matrix product operator representations B Pirvu, V Murg, J I Cirac and F Verstraete SIMULATION AND DYNAMICS A quantum differentiation of k-SAT instances B Tamir and G Ortiz Classical Ising model test for quantum circuits Joseph Geraci and Daniel A Lidar Exact matrix product solutions in the Heisenberg picture of an open quantum spin chain S R Clark, J Prior, M J Hartmann, D Jaksch and M B Plenio Exact solution of Markovian master equations for quadratic Fermi systems: thermal baths, open XY spin chains and non-equilibrium phase transition Tomaž Prosen and Bojan Žunkovi? Quantum kinetic Ising models R Augusiak, F M Cucchietti, F Haake and M Lewenstein ENTANGLEMENT AND SPECTRAL PROPERTIES Ground states of unfrustrated spin Hamiltonians satisfy an area law Niel de Beaudrap, Tobias J Osborne and Jens Eisert Correlation density matrices for one-dimensional quantum chains based on the density matrix renormalization group W Münder, A Weichselbaum, A Holzner, Jan von Delft and C L Henley The invariant-comb approach and its relation to the balancedness of multipartite entangled states Andreas Osterloh and Jens Siewert Entanglement scaling of fractional quantum Hall states through geometric deformations Andreas M Läuchli, Emil J Bergholtz and Masudul Haque Entanglement versus gap for one-dimensional spin systems Daniel Gottesman and M B Hastings Entanglement spectra of critical and near-critical systems in one dimension F Pollmann and J E Moore Macroscopic bound entanglement in thermal graph states D Cavalcanti, L Aolita, A Ferraro, A García-Saez and A Acín Entanglement at the quantum phase transition in a harmonic lattice Elisabeth Rieper, Janet Anders and Vlatko Vedral Multipartite entanglement and frustration P Facchi, G Florio, U Marzolino, G Parisi and S Pascazio Entropic uncertainty relations—a survey Stephanie Wehner and Andreas Winter Entanglement in a spin system with inverse square statistical interaction D Giuliano, A Sindona, G Falcone, F Plastina and L Amico APPLICATIONS Time-dependent currents of one-dimensional bosons in an optical lattice J Schachenmayer, G Pupillo and A J Daley Implementing quantum gates using t

Eisert, Jens; Plenio, Martin B.

2010-02-01

47

Decoherence of many-body systems due to many-body interactions

We study a spin-gas model, where N{sub S} system qubits are interacting with N{sub B} bath qubits via many-body interactions. We consider multipartite Ising interactions and show how the effect of decoherence depends on the specific coupling between the system and its environment. For instance, we analyze the influence of decoherence induced by k-body interactions for different values of k. Moreover, we study how the effect of decoherence depends on the correlation between bath qubits that are coupled to different individual system qubits and compare Markovian with non-Markovian scenarios. We derive a useful canonical form of a completely positive map that describes a class of system environment interactions with a finite size of environment correlations. As examples we consider specific quantum many-body states and investigate their evolution under different decoherence models. As a complementary investigation, we study how the coupling to the environment can be employed to generate a desired multipartite state.

Carle, T.; Kraus, B. [Institute for Theoretical Physics, University of Innsbruck, Innsbruck (Austria); Briegel, H. J. [Institute for Theoretical Physics, University of Innsbruck, Innsbruck (Austria); Institute for Quantum Optics and Quantum Information, Austrian Academy of Science, Innsbruck (Austria)

2011-07-15

48

Analyzing Many-Body Localization with a Quantum Computer

NASA Astrophysics Data System (ADS)

Many-body localization, the persistence against electron-electron interactions of the localization of states with nonzero excitation energy density, poses a challenge to current methods of theoretical and numerical analyses. Numerical simulations have so far been limited to a small number of sites, making it difficult to obtain reliable statements about the thermodynamic limit. In this paper, we explore the ways in which a relatively small quantum computer could be leveraged to study many-body localization. We show that, in addition to studying time evolution, a quantum computer can, in polynomial time, obtain eigenstates at arbitrary energies to sufficient accuracy that localization can be observed. The limitations of quantum measurement, which preclude the possibility of directly obtaining the entanglement entropy, make it difficult to apply some of the definitions of many-body localization used in the recent literature. We discuss alternative tests of localization that can be implemented on a quantum computer.

Bauer, Bela; Nayak, Chetan

2014-10-01

49

Analyzing many-body localization with a quantum computer

Many-body localization, the persistence against electron-electron interactions of the localization of states with non-zero excitation energy density, poses a challenge to current methods of theoretical and numerical analysis. Numerical simulations have so far been limited to a small number of sites, making it difficult to obtain reliable statements about the thermodynamic limit. In this paper, we explore the ways in which a relatively small quantum computer could be leveraged to study many-body localization. We show that, in addition to studying time-evolution, a quantum computer can, in polynomial time, obtain eigenstates at arbitrary energies to sufficient accuracy that localization can be observed. The limitations of quantum measurement, which preclude the possibility of directly obtaining the entanglement entropy, make it difficult to apply some of the definitions of many-body localization used in the recent literature. We discuss alternative tests of localization that can be implemented on a quantum computer.

Bela Bauer; Chetan Nayak

2014-07-07

50

Studying many-body physics through quantum coding theory

The emerging closeness between correlated spin systems and error-correcting codes enables us to use coding theoretical techniques to study physical properties of many-body spin systems. This thesis illustrates the use of ...

Yoshida, Beni

2012-01-01

51

Computational Nuclear Quantum Many-Body Problem: The UNEDF Project

The UNEDF project was a large-scale collaborative effort that applied high-performance computing to the nuclear quantum many-body problem. UNEDF demonstrated that close associations among nuclear physicists, mathematicians, and computer scientists can lead to novel physics outcomes built on algorithmic innovations and computational developments. This review showcases a wide range of UNEDF science results to illustrate this interplay.

Scott Bogner; Aurel Bulgac; Joseph A. Carlson; Jonathan Engel; George Fann; Richard J. Furnstahl; Stefano Gandolfi; Gaute Hagen; Mihai Horoi; Calvin W. Johnson; Markus Kortelainen; Ewing Lusk; Pieter Maris; Hai Ah Nam; Petr Navratil; Witold Nazarewicz; Esmond G. Ng; Gustavo P. A. Nobre; Erich Ormand; Thomas Papenbrock; Junchen Pei; Steven C. Pieper; Sofia Quaglioni; Kenneth J. Roche; Jason Sarich; Nicolas Schunck; Masha Sosonkina; Jun Terasaki; Ian J. Thompson; James P. Vary; Stefan M. Wild

2013-04-12

52

Quantum many body physics in single and bilayer graphene

Two dimensional electron systems (2DES) provide a uniquely promising avenue for investigation of many body physics. Graphene constitutes a new and unusual 2DES, which may give rise to unexpected collective phenomena. ...

Nandkishore, Rahul (Rahul Mahajan )

2012-01-01

53

Understanding the physical properties of strongly interacting many-electron systems remains one of the central goals of condensed matter physics. In this project, the authors have developed and implemented numerical techniques, such as quantum Monte Carlo simulations, to study basic models of interacting electrons: the one-band Hubbard model for positive and negative U, the three-band CuO{sub 2} Hubbard model, the Holstein electron-phonon model, the periodic Anderson model, and the Kondo lattice. Such models exhibit a rich variety of physical properties. For example, the half-filled Holstein model undergoes a Peierls-charge-density wave transition. While away from half-filling there is competition between superconductivity and the Peierls-charge-density wave phase. The ground state of the half-filled 2D Hubbard model has long-range antiferromagnetic order. Away from half-filling, it has been found to have an attractive interaction in the singlet d{sub x{sup 2}{minus}y{sup 2}} pairing channel, and it provides a model for the high-temperature cuprate superconductors. Similarly, it is believed that the periodic Anderson model and the Kondo lattice model provide a framework for understanding the heavy fermion materials which can exhibit antiferromagnetic and superconducting phases. Because of the strong coupling and the interplay between the different correlations, it is possible to tip these delicately balanced systems in favor of a given correlated state by the approximations one makes. Thus it is important to develop systematic, controlled calculations for these models. Numerical calculations provide an important approach for determining the properties of such models. A review of the work on these problems is presented.

Scalapino, D.J.; Sugar, R.L.

1993-12-31

54

Entanglement replication in driven-dissipative many body systems

We study the dissipative dynamics of two independent arrays of many-body systems, locally driven by a common entangled field. We show that in the steady state the entanglement of the driving field is reproduced in an arbitrarily large series of inter-array entangled pairs over all distances. Local nonclassical driving thus realizes a scale-free entanglement replication and long-distance entanglement distribution mechanism that has immediate bearing on the implementation of quantum communication networks.

S. Zippilli; M. Paternostro; G. Adesso; F. Illuminati

2012-04-25

55

Many-body energy localization transition in periodically driven systems

According to the second law of thermodynamics the total entropy of a system is increased during almost any dynamical process. The positivity of the specific heat implies that the entropy increase is associated with heating. This is generally true both at the single particle level, like in the Fermi acceleration mechanism of charged particles reflected by magnetic mirrors, and for complex systems in everyday devices. Notable exceptions are known in noninteracting systems of particles moving in periodic potentials. Here the phenomenon of dynamical localization can prevent heating beyond certain threshold. The dynamical localization is known to occur both at classical (Fermi–Ulam model) and at quantum levels (kicked rotor). However, it was believed that driven ergodic systems will always heat without bound. Here, on the contrary, we report strong evidence of dynamical localization transition in both classical and quantum periodically driven ergodic systems in the thermodynamic limit. This phenomenon is reminiscent of many-body localization in energy space. -- Highlights: •A dynamical localization transition in periodically driven ergodic systems is found. •This phenomenon is reminiscent of many-body localization in energy space. •Our results are valid for classical and quantum systems in the thermodynamic limit. •At critical frequency, the short time expansion for the evolution operator breaks down. •The transition is associated to a divergent time scale.

D’Alessio, Luca, E-mail: dalessio@buphy.bu.edu [Physics Department, Boston University, Boston, MA 02215 (United States) [Physics Department, Boston University, Boston, MA 02215 (United States); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Polkovnikov, Anatoli, E-mail: asp@bu.edu [Physics Department, Boston University, Boston, MA 02215 (United States)] [Physics Department, Boston University, Boston, MA 02215 (United States)

2013-06-15

56

Dissipative many-body quantum optics in Rydberg media.

We develop a theoretical framework for the dissipative propagation of quantized light under conditions of electromagnetically induced transparency in atomic media involving strongly interacting Rydberg states. The theory allows us to determine the peculiar spatiotemporal structure of the output of the recently demonstrated single-photon filter and the recently proposed single-photon subtractor, which, respectively, let through and absorb a single photon. In addition to being crucial for applications of these and other optical quantum devices, the theory opens the door to the study of exotic dissipative many-body dynamics of strongly interacting photons in nonlinear nonlocal media. PMID:25167264

Gorshkov, Alexey V; Nath, Rejish; Pohl, Thomas

2013-04-12

57

Ideal quantum glass transitions: Many-body localization without quenched disorder

NASA Astrophysics Data System (ADS)

We explore the possibility for translationally invariant quantum many-body systems to undergo a dynamical glass transition, at which ergodicity and translational invariance break down spontaneously, driven entirely by quantum effects. In contrast to analogous classical systems, where the existence of such an ideal glass transition remains a controversial issue, a genuine phase transition is predicted in the quantum regime. This ideal quantum glass transition can be regarded as a many-body localization transition due to self-generated disorder. Despite their lack of thermalization, these disorder-free quantum glasses do not possess an extensive set of local conserved operators, unlike what is conjectured for many-body localized systems with strong quenched disorder.

Schiulaz, M.; Müller, M.

2014-08-01

58

Preparation of many-body states for quantum simulation

While quantum computers are capable of simulating many quantum systems efficiently, the simulation algorithms must begin with the preparation of an appropriate initial state. We present a method for generating physically relevant quantum states on a lattice in real space. In particular, the present algorithm is able to prepare general pure and mixed many-particle states of any number of particles. It relies on a procedure for converting from a second-quantized state to its first-quantized counterpart. The algorithm is efficient in that it operates in time that is polynomial in all the essential descriptors of the system, such the number of particles, the resolution of the lattice, and the inverse of the maximum final error. This scaling holds under the assumption that the wavefunction to be prepared is bounded or its indefinite integral known and that the Fock operator of the system is efficiently simulatable.

Nicholas J. Ward; Ivan Kassal; Alán Aspuru-Guzik

2008-12-14

59

The nuclear shell model as a testing ground for many-body quantum chaos

Atomic nuclei analyzed in the framework of the shell model provide a good example of a many-body quantum system with strong interactions between its constituents. As excitation energy and level density increase, the system evolves in the direction of very complicated (“stochastic”) dynamics. Energy levels and stationary wave functions obtained in realistic shell-model calculations are studied from the viewpoint of

Vladimir Zelevinsky; B. Alex Brown; Njema Frazier; Mihai Horoi

1996-01-01

60

Petascale Many Body Methods for Complex Correlated Systems

NASA Astrophysics Data System (ADS)

Correlated systems constitute an important class of materials in modern condensed matter physics. Correlation among electrons are at the heart of all ordering phenomena and many intriguing novel aspects, such as quantum phase transitions or topological insulators, observed in a variety of compounds. Yet, theoretically describing these phenomena is still a formidable task, even if one restricts the models used to the smallest possible set of degrees of freedom. Here, modern computer architectures play an essential role, and the joint effort to devise efficient algorithms and implement them on state-of-the art hardware has become an extremely active field in condensed-matter research. To tackle this task single-handed is quite obviously not possible. The NSF-OISE funded PIRE collaboration ``Graduate Education and Research in Petascale Many Body Methods for Complex Correlated Systems'' is a successful initiative to bring together leading experts around the world to form a virtual international organization for addressing these emerging challenges and educate the next generation of computational condensed matter physicists. The collaboration includes research groups developing novel theoretical tools to reliably and systematically study correlated solids, experts in efficient computational algorithms needed to solve the emerging equations, and those able to use modern heterogeneous computer architectures to make then working tools for the growing community.

Pruschke, Thomas

2012-02-01

61

Many-body interactions with single-electron quantum dots for topological quantum computation

We show that a many-body system of single-electron quantum dots, whose orbital states are dressed by a global magnetic field, can be described by an effective Hamiltonian with an anisotropic XZ spin-spin interaction which is proportional to the Zeeman splitting. We show that these interaction potentials give rise to spin-dependent Hubbard models with tunable nearest neighbor two-body and three-body interactions. The two-body interactions can even be switched off via the external electric field, and hence the three-body interaction plays a dominant role. The derivation of these effective interaction potentials follows from a well-controlled and systematic expansion into many-body interaction terms. Models of this type have appeared in the recent discussion of exotic quantum phases, in particular in the context of topological quantum phases and quantum computing, and we show that quantum dots can be regarded as a realistic experimental route which provides the basic building blocks and techniques toward the study of these phenomena. The main application of this derived model is to develop topological quantum computation.

Xue Peng [Department of Physics, Southeast University, Nanjing 211189 (China)

2010-05-15

62

Interrogating the void : the difficulty of extracting information from many-body systems

In this thesis, I will explore some of the ways the information-theoretic properties of quantum many-body systems can be analyzed. I do this in two different settings. First, I will describe an approach to the "scrambling ...

Diab, Kenan S. (Kenan Sebastian)

2011-01-01

63

Lattice methods for strongly interacting many-body systems

Lattice field theory methods, usually associated with non-perturbative studies of quantum chromodynamics, are becoming increasingly common in the calculation of ground-state and thermal properties of strongly interacting non-relativistic few- and many-body systems, blurring the interfaces between condensed matter, atomic and low-energy nuclear physics. While some of these techniques have been in use in the area of condensed matter physics for a long time, others, such as hybrid Monte Carlo and improved effective actions, have only recently found their way across areas. With this topical review, we aim to provide a modest overview and a status update on a few notable recent developments. For the sake of brevity we focus on zero-temperature, non-relativistic problems. After a short introduction, we lay out some general considerations and proceed to discuss sampling algorithms, observables, and systematic effects. We show selected results on ground- and excited-state properties of fermions in the limit of unitarity. The appendix contains details on group theory on the lattice.

Joaquín E. Drut; Amy N. Nicholson

2012-08-31

64

Dynamical studies of collective behavior of many-body systems

This thesis contains the results of the study of the emergent properties of two classes of many-body systems using computational and analytical techniques. (1) The translational and rotational motion of a sphere in a viscous Lennard-Jones liquid has been studied using molecular dynamics simulations. The drag and torque on a sphere in an effectively unbounded fluid are found to agree

Maxim Vergeles

1997-01-01

65

We construct a quantum Monte Carlo algorithm for interacting fermions using the two-body density as the fundamental quantity. The central idea is mapping the interacting fermionic system onto an auxiliary system of interacting bosons. The correction term is approximated using correlated wave functions for the interacting system, resulting in an effective potential that represents the nodal surface. We calculate the

Balázs Hetényi; L. Brualla; S. Fantoni

2004-01-01

66

NASA Astrophysics Data System (ADS)

We construct a quantum Monte Carlo algorithm for interacting fermions using the two-body density as the fundamental quantity. The central idea is mapping the interacting fermionic system onto an auxiliary system of interacting bosons. The correction term is approximated using correlated wave functions for the interacting system, resulting in an effective potential that represents the nodal surface. We calculate the properties of 3He and find good agreement with experiment and with other theoretical work. In particular, our results for the total energy agree well with other calculations where the same approximations were implemented but the standard quantum Monte Carlo algorithm was used.

Hetényi, Balázs; Brualla, L.; Fantoni, S.

2004-10-01

67

We construct a quantum Monte Carlo algorithm for interacting fermions using the two-body density as the fundamental quantity. The central idea is mapping the interacting fermionic system onto an auxiliary system of interacting bosons. The correction term is approximated using correlated wave functions for the interacting system, resulting in an effective potential that represents the nodal surface. We calculate the properties of 3He and find good agreement with experiment and with other theoretical work. In particular, our results for the total energy agree well with other calculations where the same approximations were implemented but the standard quantum Monte Carlo algorithm was used. PMID:15525051

Hetényi, Balázs; Brualla, L; Fantoni, S

2004-10-22

68

Porter-Thomas distribution in unstable many-body systems

We use the continuum shell model approach to explore the resonance width distribution in unstable many-body systems. The single-particle nature of a decay, the few-body character of the interaction Hamiltonian, and the collectivity that emerges in nonstationary systems due to the coupling to the continuum of reaction states are discussed. Correlations between the structures of the parent and daughter nuclear systems in the common Fock space are found to result in deviations of decay width statistics from the Porter-Thomas distribution.

Volya, Alexander [Department of Physics, Florida State University, Tallahassee, Florida 32306-4350 (United States)

2011-04-15

69

Adiabatic approximations are a powerful tool for simplifying nonlinear quantum dynamics, and are applicable whenever a system exhibits a hierarchy of time scales. Current interest in small nonlinear quantum systems, such as few-mode Bose-Hubbard models, warrants further development of adiabatic methods in the particular context of these models. Here we extend our recent work on a simple four-mode Bose-Hubbard model with two distinct dynamical time scales, in which we showed that among the perturbations around excited stationary states of the system is a slow collective excitation that is not present in the Bogoliubov spectrum. We characterized this mode as a resonant energy exchange with its frequency shifted by nonlinear effects, and referred to it as a second Josephson oscillation, in analogy with the second sound mode of liquid helium II. We now generalize our previous theory beyond the mean field regime, and construct a general Bogoliubov free quasiparticle theory that explicitly respects the system's adiabatic invariant as well the exact conservation of particles. We compare this theory to the numerically exact quantum energy spectrum with up to forty particles, and find good agreement over a significant range of parameter space.

M. P. Strzys; J. R. Anglin

2011-12-21

70

Many-Body Green Function of Degenerate Systems

A rigorous nonperturbative adiabatic approximation of the evolution operator in the many-body physics of degenerate systems is derived. This approximation is used to solve the long-standing problem of the choice of the initial states of H{sub 0} leading to eigenstates of H{sub 0}+V for degenerate systems. These initial states are eigenstates of P{sub 0}VP{sub 0}, where P{sub 0} is the projection onto a degenerate eigenspace of H{sub 0}. This result is used to give the proper definition of the Green function, the statistical Green function and the nonequilibrium Green function of degenerate systems. The convergence of these Green functions is established.

Brouder, Christian [Institut de Mineralogie et de Physique des Milieux Condenses, CNRS UMR 7590, Universites Paris 6 et 7, IPGP, 140 rue de Lourmel, 75015 Paris (France); Panati, Gianluca [Dipartimento di Matematica, Universita di Roma La Sapienza, Roma (Italy); Stoltz, Gabriel [Universite Paris Est, CERMICS, Projet MICMAC ENPC-INRIA, 6 and 8 Avenue Pascal, 77455 Marne-la-Vallee Cedex 2 (France)

2009-12-04

71

Cooling through quantum criticality and many-body effects in condensed matter and cold gases

NASA Astrophysics Data System (ADS)

This article reviews some recent developments for new cooling technologies in the fields of condensed matter physics and cold gases, both from an experimental and theoretical point of view. The main idea is to make use of distinct many-body interactions of the system to be cooled which can be some cooling stage or the material of interest itself, as is the case in ultracold gases. For condensed matter systems, we discuss magnetic cooling schemes based on a large magnetocaloric effect as a result of a nearby quantum phase transition and consider effects of geometrical frustration. For ultracold gases, we review many-body cooling techniques, such as spin-gradient and Pomeranchuk cooling, which can be applied in the presence of an optical lattice. We compare the cooling performance of these new techniques with that of conventional approaches and discuss state-of-the-art applications.

Wolf, Bernd; Honecker, Andreas; Hofstetter, Walter; Tutsch, Ulrich; Lang, Michael

2014-10-01

72

Experimental quantum simulations of many-body physics with trapped ions

NASA Astrophysics Data System (ADS)

Direct experimental access to some of the most intriguing quantum phenomena is not granted due to the lack of precise control of the relevant parameters in their naturally intricate environment. Their simulation on conventional computers is impossible, since quantum behaviour arising with superposition states or entanglement is not efficiently translatable into the classical language. However, one could gain deeper insight into complex quantum dynamics by experimentally simulating the quantum behaviour of interest in another quantum system, where the relevant parameters and interactions can be controlled and robust effects detected sufficiently well. Systems of trapped ions provide unique control of both the internal (electronic) and external (motional) degrees of freedom. The mutual Coulomb interaction between the ions allows for large interaction strengths at comparatively large mutual ion distances enabling individual control and readout. Systems of trapped ions therefore exhibit a prominent system in several physical disciplines, for example, quantum information processing or metrology. Here, we will give an overview of different trapping techniques of ions as well as implementations for coherent manipulation of their quantum states and discuss the related theoretical basics. We then report on the experimental and theoretical progress in simulating quantum many-body physics with trapped ions and present current approaches for scaling up to more ions and more-dimensional systems.

Schneider, Ch; Porras, Diego; Schaetz, Tobias

2012-02-01

73

Experimental quantum simulations of many-body physics with trapped ions.

Direct experimental access to some of the most intriguing quantum phenomena is not granted due to the lack of precise control of the relevant parameters in their naturally intricate environment. Their simulation on conventional computers is impossible, since quantum behaviour arising with superposition states or entanglement is not efficiently translatable into the classical language. However, one could gain deeper insight into complex quantum dynamics by experimentally simulating the quantum behaviour of interest in another quantum system, where the relevant parameters and interactions can be controlled and robust effects detected sufficiently well. Systems of trapped ions provide unique control of both the internal (electronic) and external (motional) degrees of freedom. The mutual Coulomb interaction between the ions allows for large interaction strengths at comparatively large mutual ion distances enabling individual control and readout. Systems of trapped ions therefore exhibit a prominent system in several physical disciplines, for example, quantum information processing or metrology. Here, we will give an overview of different trapping techniques of ions as well as implementations for coherent manipulation of their quantum states and discuss the related theoretical basics. We then report on the experimental and theoretical progress in simulating quantum many-body physics with trapped ions and present current approaches for scaling up to more ions and more-dimensional systems. PMID:22790343

Schneider, Ch; Porras, Diego; Schaetz, Tobias

2012-02-01

74

Dynamical studies of collective behavior of many-body systems

NASA Astrophysics Data System (ADS)

This thesis contains the results of the study of the emergent properties of two classes of many-body systems using computational and analytical techniques. (1) The translational and rotational motion of a sphere in a viscous Lennard-Jones liquid has been studied using molecular dynamics simulations. The drag and torque on a sphere in an effectively unbounded fluid are found to agree with continuum hydrodynamics results even when the size of the sphere is comparable to that of the fluid molecules. The diffusivity of a spherical tracer particle is in accord with the Stokes-Einstein relation, and the corresponding Brownian motion is determined by its interaction with the layers formed by fluid molecules around it. When a sphere moves near a solid wall, the drag and torque are found to agree with lubrication theory down to molecular scales, but the predicted divergence is regularized at very short distances due to depletion of fluid molecules near the wall and the appearance of slip at high shear stress. (2) A new mean field theory of sandpiles with dissipation introduced in a clear and physical way has been proposed. All exponents for our model have been obtained by constructing a master equation and mapping the model into a branching process. Two of the exponents are found to depend on a parameter relating the rate of dissipation to that of addition of sand grains to the system whereas the others are universal. A temperature-like parameter T has been introduced in our mean field theory of sandpiles and in growth and evolution models of self-organized criticality. In contrast with evolution and growth models, where the scaling behavior changes dramatically on the introduction of a non-zero temperature, self-organized criticality in sandpiles exists at all T

Vergeles, Maxim

75

221B Lecture Notes Many-Body Problems I (Quantum Statistics)

221B Lecture Notes Many-Body Problems I (Quantum Statistics) 1 Quantum Statistics of Identical is for bosons (particles that obey BoseÂEinstein statistics) and -1 for fermions (those that obey Fermi-Dirac statistics). The above argument is actually true only for three spatial dimensions and above. In two

Murayama, Hitoshi

76

Scale-free entanglement replication in driven-dissipative many body systems

We study the dynamics of independent arrays of many-body dissipative systems, subject to a common driving by an entangled light field. We show that in the steady state the global system orders in a series of inter-array strongly entangled pairs over all distances. Such scale-free entanglement replication and long-distance distribution mechanism has potential applications for the implementation of robust quantum networked communication.

Zippilli, S; Adesso, G; Illuminati, F

2012-01-01

77

NASA Astrophysics Data System (ADS)

We introduce quantum information engines that extract work from quantum states and a single thermal reservoir. They may operate under three general conditions—(1) unitarily steered evolution (US), driven by a restricted set of available Hamiltonians; (2) irreversible thermalization (IT), and (3) isothermal relaxation (IR)—and hence are called USITIR machines. They include novel engines without traditional feedback control mechanisms, as well as versions which also include them. Explicit constructions of USITIR engines are presented for one- and two-qubit states and their maximum extractable work is computed, which is optimal. Optimality is achieved when the notions of controllable thermalizability and density matrix controllability are fulfilled. Then many-body extensions of USITIR engines are also analyzed and conditions for optimal work extraction are identified. When they are not met, we measure their lack of optimality by means of newly defined uncontrollable entropies, which are explicitly computed for some selected examples. This includes cases of distinguishable and indistinguishable particles.

Diaz de la Cruz, J. M.; Martin-Delgado, M. A.

2014-03-01

78

Strongdeco: Expansion of analytical, strongly correlated quantum states into a many-body basis

NASA Astrophysics Data System (ADS)

We provide a Mathematica code for decomposing strongly correlated quantum states described by a first-quantized, analytical wave function into many-body Fock states. Within them, the single-particle occupations refer to the subset of Fock-Darwin functions with no nodes. Such states, commonly appearing in two-dimensional systems subjected to gauge fields, were first discussed in the context of quantum Hall physics and are nowadays very relevant in the field of ultracold quantum gases. As important examples, we explicitly apply our decomposition scheme to the prominent Laughlin and Pfaffian states. This allows for easily calculating the overlap between arbitrary states with these highly correlated test states, and thus provides a useful tool to classify correlated quantum systems. Furthermore, we can directly read off the angular momentum distribution of a state from its decomposition. Finally we make use of our code to calculate the normalization factors for Laughlin's famous quasi-particle/quasi-hole excitations, from which we gain insight into the intriguing fractional behavior of these excitations. Program summaryProgram title: Strongdeco Catalogue identifier: AELA_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELA_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 5475 No. of bytes in distributed program, including test data, etc.: 31 071 Distribution format: tar.gz Programming language: Mathematica Computer: Any computer on which Mathematica can be installed Operating system: Linux, Windows, Mac Classification: 2.9 Nature of problem: Analysis of strongly correlated quantum states. Solution method: The program makes use of the tools developed in Mathematica to deal with multivariate polynomials to decompose analytical strongly correlated states of bosons and fermions into a standard many-body basis. Operations with polynomials, determinants and permanents are the basic tools. Running time: The distributed notebook takes a couple of minutes to run.

Juliá-Díaz, Bruno; Graß, Tobias

2012-03-01

79

a Fourth Order Diffusion Monte Carlo Algorithm for Solving Quantum Many-Body Problems

We derive a fourth-order diffusion Monte Carlo algorithm for solving quantum many-body problems. The method uses a factorization of the imaginary time propagator in terms of the usual local energy E and Langevin operators L as well as an additional pseudo-potential consisting of the double commutator [EL, [L, EL

H. A. Forbert; S. A. Chin

2001-01-01

80

A fourth order diffusion Monte Carlo algorithm for solving quantum many-body problems

We derive and numerically implement a fourth order Diffusion Monte Carlo algorithm for solving quantum many-body problems. The method uses a factorization of the imaginary time propagator in terms of the usual local energy and Langevin operators as well as an additional pseudo-potential consisting of the double commutator [EL, [L, EL

Harald Alexander Forbert

1999-01-01

81

A fourth order diffusion Monte Carlo algorithm for solving quantum many-body problems

NASA Astrophysics Data System (ADS)

We derive and numerically implement a fourth order Diffusion Monte Carlo algorithm for solving quantum many-body problems. The method uses a factorization of the imaginary time propagator in terms of the usual local energy and Langevin operators as well as an additional pseudo-potential consisting of the double commutator [EL, [L, EL

Forbert, Harald Alexander

82

Many-Body Quantum Theory in Condensed Matter Physics—An Introduction

This is undoubtedly an ambitious book. It aims to provide a wide ranging, yet self-contained and pedagogical introduction to techniques of quantum many-body theory in condensed matter physics, without losing mathematical `rigor' (which I hope means rigour), and with an eye on physical insight, motivation and application. The authors certainly bring plenty of experience to the task, the book having

D E Logan

2005-01-01

83

BOOK REVIEW: Many-Body Quantum Theory in Condensed Matter Physics---An Introduction

This is undoubtedly an ambitious book. It aims to provide a wide ranging, yet self-contained and pedagogical introduction to techniques of quantum many-body theory in condensed matter physics, without losing mathematical `rigor' (which I hope means rigour), and with an eye on physical insight, motivation and application. The authors certainly bring plenty of experience to the task, the book having

H. Bruus; K. Flensberg

2005-01-01

84

Functional-Integral Approach to Non-Equilibrium Quantum Many-Body Dynamics

NASA Astrophysics Data System (ADS)

We discuss the functional-integral approach to far-from-equilibrium quantum many-body dynamics. Specific techniques considered include the two-particle-irreducible effective action and the real-time flow-equation approach. Different applications, including equilibration after a sudden parameter change and non-equilibrium critical phenomena, illustrate the potential of these methods.

Bodet, Cédric; Kronenwett, Matthias; Nowak, Boris; Sexty, Dénes; Gasenzer, Thomas

2013-02-01

85

Static self-gravitating many-body systems in Einstein gravity

We consider the problem of constructing static, elastic, many-body systems in Einstein gravity. The solutions constructed are deformations of static many-body configurations in Newtonian gravity. No symmetry assumptions are made.

Lars Andersson; Berndt G. Schmidt

2009-05-08

86

PREFACE: Advanced many-body and statistical methods in mesoscopic systems

NASA Astrophysics Data System (ADS)

It has increasingly been realized in recent times that the borders separating various subfields of physics are largely artificial. This is the case for nanoscale physics, physics of lower-dimensional systems and nuclear physics, where the advanced techniques of many-body theory developed in recent times could provide a unifying framework for these disciplines under the general name of mesoscopic physics. Other fields, such as quantum optics and quantum information, are increasingly using related methods. The 6-day conference 'Advanced many-body and statistical methods in mesoscopic systems' that took place in Constanta, Romania, between 27 June and 2 July 2011 was, we believe, a successful attempt at bridging an impressive list of topical research areas: foundations of quantum physics, equilibrium and non-equilibrium quantum statistics/fractional statistics, quantum transport, phases and phase transitions in mesoscopic systems/superfluidity and superconductivity, quantum electromechanical systems, quantum dissipation, dephasing, noise and decoherence, quantum information, spin systems and their dynamics, fundamental symmetries in mesoscopic systems, phase transitions, exactly solvable methods for mesoscopic systems, various extension of the random phase approximation, open quantum systems, clustering, decay and fission modes and systematic versus random behaviour of nuclear spectra. This event brought together participants from seventeen countries and five continents. Each of the participants brought considerable expertise in his/her field of research and, at the same time, was exposed to the newest results and methods coming from the other, seemingly remote, disciplines. The talks touched on subjects that are at the forefront of topical research areas and we hope that the resulting cross-fertilization of ideas will lead to new, interesting results from which everybody will benefit. We are grateful for the financial and organizational support from IFIN-HH, Ovidius University (where the conference took place), the Academy of Romanian Scientists and the Romanian National Authority for Scientific Research. This conference proceedings volume brings together some of the invited and contributed talks of the conference. The hope of the editors is that they will constitute reference material for applying many-body techniques to problems in mesoscopic and nuclear physics. We thank all the participants for their contribution to the success of this conference. D V Anghel and D S Delion IFIN-HH, Bucharest, Romania G S Paraoanu Aalto University, Finland Conference photograph

Anghel, Dragos Victor; Sabin Delion, Doru; Sorin Paraoanu, Gheorghe

2012-02-01

87

Exact solvability of interacting many body lattice systems

We address the problem of exactly describing stochastic nonequilibrium systems that are widely used to model one-dimensional\\u000a transport, in biology, traffic flow and others. We review the matrix product states ansatz to interacting multiparticle systems\\u000a and its extension to a tridiagonal (generalized Onsager) algebra approach. The stationary probability distribution is expressed\\u000a as a matrix product state with respect to a

Boyka Aneva

2010-01-01

88

Many-Body Force and Mobility Measurements in Colloidal Systems

We demonstrate a technique for simultaneously measuring each component of the\\u000aforce vectors and mobility tensor of a small collection of colloidal particles\\u000abased on observing a set of particle trajectories. For a few-body system of\\u000amicron-sized polymer beads in oil separated by several particle radii, we find\\u000athat the mobility tensor is well-described by a pairwise Stokeslet model. This

Jason W. Merrill; Sunil K. Sainis; Eric R. Dufresne

2009-01-01

89

Many-Body Force and Mobility Measurements in Colloidal Systems

We demonstrate a technique for simultaneously measuring each component of the force vectors and mobility tensor of a small collection of colloidal particles based on observing a set of particle trajectories. For a few-body system of micron-sized polymer beads in oil separated by several particle radii, we find that the mobility tensor is well-described by a pairwise Stokeslet model. This

Jason W. Merrill; Sunil K. Sainis; Jerzy Blawzdziewicz; Eric R. Dufresne

2009-01-01

90

Dynamic correlations in Brownian many-body systems

NASA Astrophysics Data System (ADS)

For classical Brownian systems driven out of equilibrium, we derive inhomogeneous two-time correlation functions from functional differentiation of the one-body density and current with respect to external fields. In order to allow for appropriate freedom upon building the derivatives, we formally supplement the Smoluchowski dynamics by a source term, which vanishes at the physical solution. These techniques are applied to obtain a complete set of dynamic Ornstein-Zernike equations, which serve for the development of approximation schemes. The rules of functional calculus lead naturally to non-Markovian equations of motion for the two-time correlators. Memory functions are identified as functional derivatives of a unique space- and time-nonlocal dissipation power functional.

Brader, Joseph M.; Schmidt, Matthias

2014-01-01

91

Dynamic correlations in Brownian many-body systems

For classical Brownian systems driven out of equilibrium we derive inhomogeneous two-time correlation functions from functional differentiation of the one-body density and current with respect to external fields. In order to allow for appropriate freedom upon building the derivatives, we formally supplement the Smoluchowski dynamics by a source term, which vanishes at the physical solution. These techniques are applied to obtain a complete set of dynamic Ornstein-Zernike equations, which serve for the development of approximation schemes. The rules of functional calculus lead naturally to non-Markovian equations of motion for the two-time correlators. Memory functions are identified as functional derivatives of a unique space- and time-nonlocal dissipation power functional.

Joseph M. Brader; Matthias Schmidt

2013-10-30

92

Emergent Localization from Many-Body Physics in Clean Quantum Point Contacts

NASA Astrophysics Data System (ADS)

Quantized conductance in quantum point contacts (QPCs) is the signature of control over electron transport at the nanoscale. As a function of channel width the conductance then increases in steps of G0=2e^2/h. However, experiments often show an additional feature with a conductance plateau near 0.7G0, known as the 0.7 anomaly. This has been studied since 1995 but its full understanding is still an open problem. Spontaneous localization due to many-body effects in open QPCs, and the associated Kondo effect, has emerged as a promising theory for the 0.7 anomaly [1]. This theory work predicted that the many-body effects should for certain QPC geometries not give a single localized state but a pair of localized states, but signatures of this were till now not reported. For the first time, we have fabricated length-tunable QPCs in clean semiconductors and we discovered a periodic modulation of the 0.7 anomaly as a function of length. This modulation correlates with signatures for single and paired quasi-localized states, in the form of single- and two-impurity Kondo physics. Our results demonstrate that Friedel oscillations and emergent impurity states from many-body physics are fundamental to these phenomena. [1] T. Rejec and Y. Meir, Nature 442, 900 (2006).

van der Wal, Caspar H.; Iqbal, M. J.; Koop, E. J.; Dekker Dekker, J. B.; de Jong, J. P.; van der Velde, J. H. M.; Reuter, D.; Wieck, A. D.; Aguado, R.; Meir, Y.

2013-03-01

93

On the rate of convergence for the mean field approximation of many-body quantum dynamics

We consider the time evolution of quantum states by many-body Schr\\"odinger dynamics and study the rate of convergence of their reduced density matrices in the mean field limit. If the prepared state at initial time is of coherent or factorized type and the number of particles $n$ is large enough then it is known that $1/n$ is the correct rate of convergence at any time. We show in the simple case of bounded pair potentials that the previous rate of convergence holds in more general situations with possibly correlated prepared states. In particular, it turns out that the coherent structure at initial time is unessential and the important fact is rather the speed of convergence of all reduced density matrices of the prepared states. We illustrate our result with several numerical simulations and examples of multi-partite entangled quantum states borrowed from quantum information.

Zied Ammari; Marco Falconi; Boris Pawilowski

2014-11-23

94

The structure of many-body entanglement

In this thesis we discuss the general spatial structure of quantum entanglement in local many-body systems. A central theme is the organizing power of the renormalization group for thinking about many-body entanglement. ...

Swingle, Brian Gordon

2011-01-01

95

Cavity quantum electrodynamics with many-body states of a two-dimensional electron gas.

Light-matter interaction has played a central role in understanding as well as engineering new states of matter. Reversible coupling of excitons and photons enabled groundbreaking results in condensation and superfluidity of nonequilibrium quasiparticles with a photonic component. We investigated such cavity-polaritons in the presence of a high-mobility two-dimensional electron gas, exhibiting strongly correlated phases. When the cavity was on resonance with the Fermi level, we observed previously unknown many-body physics associated with a dynamical hole-scattering potential. In finite magnetic fields, polaritons show distinct signatures of integer and fractional quantum Hall ground states. Our results lay the groundwork for probing nonequilibrium dynamics of quantum Hall states and exploiting the electron density dependence of polariton splitting so as to obtain ultrastrong optical nonlinearities. PMID:25278508

Smolka, Stephan; Wuester, Wolf; Haupt, Florian; Faelt, Stefan; Wegscheider, Werner; Imamoglu, Ataç

2014-10-17

96

BOOK REVIEW: Many-Body Quantum Theory in Condensed Matter Physics—An Introduction

NASA Astrophysics Data System (ADS)

This is undoubtedly an ambitious book. It aims to provide a wide ranging, yet self-contained and pedagogical introduction to techniques of quantum many-body theory in condensed matter physics, without losing mathematical `rigor' (which I hope means rigour), and with an eye on physical insight, motivation and application. The authors certainly bring plenty of experience to the task, the book having grown out of their graduate lectures at the Niels Bohr Institute in Copenhagen over a five year period, with the feedback and refinement this presumably brings. The book is also of course ambitious in another sense, for it competes in the tight market of general graduate/advanced undergraduate texts on many-particle physics. Prospective punters will thus want reasons to prefer it to, or at least give it space beside, well established texts in the field. Subject-wise, the book is a good mix of the ancient and modern, the standard and less so. Obligatory chapters deal with the formal cornerstones of many-body theory, from second quantization, time-dependence in quantum mechanics and linear response theory, to Green's function and Feynman diagrams. Traditional topics are well covered, including two chapters on the electron gas, chapters on phonons and electron phonon coupling, and a concise account of superconductivity (confined, no doubt judiciously, to the conventional BCS case). Less mandatory, albeit conceptually vital, subjects are also aired. These include a chapter on Fermi liquid theory, from both semi-classical and microscopic perspectives, and a freestanding account of one-dimensional electron gases and Luttinger liquids which, given the enormity of the topic, is about as concise as it could be without sacrificing clarity. Quite naturally, the authors' own interests also influence the choice of material covered. A persistent theme, which brings a healthy topicality to the book, is the area of transport in mesoscopic systems or nanostructures. Two chapters, some fifty pages of the book, are devoted to electron transport in mesoscopic systems; the one on interacting systems is preceded by a brief account of equation of motion techniques a relative rarity in a general text, used here to provide background to subsequent discussion of the Coulomb blockade in quantum dots. So does it work, and will it find a niche beside other established, wide ranging texts? On the whole I think the answer has to be yes. To begin with, the book is well organised and user-friendly, which must surely appeal to students (and their mentors). The chapters are typically bite-sized and digestible. Each is accompanied by a summary/outlook, which in doing just that attempts to place the specific topic in a wider context, together with a set of problems that illustrate, and in many cases expand substantially on, the basic subject matter. A particularly healthy feature of the book is the extent to which the authors have sought where possible to include physical and/or material applications of basic theory, thereby enlivening old material and enhancing appreciation of the new. The first chapter on the electron gas, for example, introduces the reader to a range of material examples, including 2D heterostructures, carbon nanotubes and quantum dots. A chapter on the formalism of Green's functions takes time out to explain how the single-particle spectral function can be measured by tunnelling spectroscopy, while discussion of impurity scattering and conductivity is refreshed by consideration of weak localization in bulk and mesoscopic systems, and the phenomenon of universal conductance fluctuations. And so on: in a text that could readily descend to the purely formal, the authors have clearly taken seriously the task of incorporating relevant, topical applications of the underlying theory. In a book as wide ranging as this any reviewer is of course bound to perceive the occasional deficiency. I felt for example that some aspects of the discussion of conductance in quantum dots, notably the Coulomb blockade and the Kondo effect, were not quite up to scratch

Logan, D. E.

2005-02-01

97

NASA Astrophysics Data System (ADS)

We study a new class of unconventional critical phenomena that is characterized by singularities only in dynamical quantities and has no thermodynamic signatures. One example of such a transition is the recently proposed many-body localization-delocalization transition, in which transport coefficients vanish at a critical temperature with no singularities in thermodynamic observables. Describing this purely dynamical quantum criticality is technically challenging as understanding the finite-temperature dynamics necessarily requires averaging over a large number of matrix elements between many-body eigenstates. Here, we develop a real-space renormalization group method for excited states that allows us to overcome this challenge in a large class of models. We characterize a specific example: the 1 D disordered transverse-field Ising model with generic interactions. While thermodynamic phase transitions are generally forbidden in this model, using the real-space renormalization group method for excited states we find a finite-temperature dynamical transition between two localized phases. The transition is characterized by nonanalyticities in the low-frequency heat conductivity and in the long-time (dynamic) spin correlation function. The latter is a consequence of an up-down spin symmetry that results in the appearance of an Edwards-Anderson-like order parameter in one of the localized phases.

Pekker, David; Refael, Gil; Altman, Ehud; Demler, Eugene; Oganesyan, Vadim

2014-01-01

98

Radiative heat transfer in anisotropic many-body systems: Tuning and enhancement

NASA Astrophysics Data System (ADS)

A general formalism for calculating the radiative heat transfer in many body systems with anisotropic component is presented. Our scheme extends the theory of radiative heat transfer in isotropic many body systems to anisotropic cases. In addition, the radiative heating of the particles by the thermal bath is taken into account in our formula. It is shown that the radiative heat exchange (HE) between anisotropic particles and their radiative cooling/heating (RCH) could be enhanced several order of magnitude than that of isotropic particles. Furthermore, we demonstrate that both the HE and RCH can be tuned dramatically by particles relative orientation in many body systems.

Nikbakht, Moladad

2014-09-01

99

Many-body Effects in a Laterally Inhomogeneous Semiconductor Quantum Well

NASA Technical Reports Server (NTRS)

Many body effects on conduction and diffusion of electrons and holes in a semiconductor quantum well are studied using a microscopic theory. The roles played by the screened Hartree-Fock (SHE) terms and the scattering terms are examined. It is found that the electron and hole conductivities depend only on the scattering terms, while the two-component electron-hole diffusion coefficients depend on both the SHE part and the scattering part. We show that, in the limit of the ambipolax diffusion approximation, however, the diffusion coefficients for carrier density and temperature are independent of electron-hole scattering. In particular, we found that the SHE terms lead to a reduction of density-diffusion coefficients and an increase in temperature-diffusion coefficients. Such a reduction or increase is explained in terms of a density-and temperature dependent energy landscape created by the bandgap renormalization.

Ning, Cun-Zheng; Li, Jian-Zhong; Biegel, Bryan A. (Technical Monitor)

2002-01-01

100

Renormalization of myoglobin-ligand binding energetics by quantum many-body effects

We carry out a first-principles atomistic study of the electronic mechanisms of ligand binding and discrimination in the myoglobin protein. Electronic correlation effects are taken into account using one of the most advanced methods currently available, namely a linear-scaling density functional theory (DFT) approach wherein the treatment of localized iron 3d electrons is further refined using dynamical mean-field theory. This combination of methods explicitly accounts for dynamical and multireference quantum physics, such as valence and spin fluctuations, of the 3d electrons, while treating a significant proportion of the protein (more than 1,000 atoms) with DFT. The computed electronic structure of the myoglobin complexes and the nature of the Fe–O2 bonding are validated against experimental spectroscopic observables. We elucidate and solve a long-standing problem related to the quantum-mechanical description of the respiration process, namely that DFT calculations predict a strong imbalance between O2 and CO binding, favoring the latter to an unphysically large extent. We show that the explicit inclusion of the many-body effects induced by the Hund’s coupling mechanism results in the correct prediction of similar binding energies for oxy- and carbonmonoxymyoglobin. PMID:24717844

Weber, Cedric; Cole, Daniel J.; O'Regan, David D.; Payne, Mike C.

2014-01-01

101

Code C# for chaos analysis of relativistic many-body systems

This work presents a new Microsoft Visual C# .NET code library, conceived as a general object oriented solution for chaos analysis of three-dimensional, relativistic many-body systems. In this context, we implemented the Lyapunov exponent and the "fragmentation level" (defined using the graph theory and the Shannon entropy). Inspired by existing studies on billiard nuclear models and clusters of galaxies, we tried to apply the virial theorem for a simplified many-body system composed by nucleons. A possible application of the "virial coefficient" to the stability analysis of chaotic systems is also discussed.

I. V. Grossu; C. Besliu; Al. Jipa; D. Felea; C. C. Bordeianu; E. Stan; T. Esanu

2008-10-03

102

We propose a new method to calculate ground state position dependent observables in quantum many-body systems. The method, which we call the path-integral diffusion Monte Carlo (PI-DMC) method, is essentially a combination of path-integral Monte Carlo (PIMC) and diffusion Monte Carlo (DMC) methods. The distribution resulting from a DMC simulation is further propagated in imaginary time by PIMC sampling. Tests

Bala´zs Hete´nyi; Eran Rabani; B. J. Berne

1999-01-01

103

We propose a new method to calculate ground state position dependent observables in quantum many-body systems. The method, which we call the path-integral diffusion Monte Carlo ~PI-DMC! method, is essentially a combination of path-integral Monte Carlo ~PIMC! and diffusion Monte Carlo ~DMC! methods. The distribution resulting from a DMC simulation is further propagated in imaginary time by PIMC sampling. Tests

Balazs Hetenyi; Eran Rabani; B. J. Berne

104

NASA Astrophysics Data System (ADS)

Treating both many-body polarization and dispersion interactions is now recognized as a key element in achieving the level of atomistic modeling required to reveal novel physics in complex systems. The quantum Drude oscillator (QDO), a Gaussian-based, coarse grained electronic structure model, captures both many-body polarization and dispersion and has linear scale computational complexity with system size, hence it is a leading candidate next-generation simulation method. Here, we investigate the extent to which the QDO treatment reproduces the desired long-range atomic and molecular properties. We present closed form expressions for leading order polarizabilities and dispersion coefficients and derive invariant (parameter-free) scaling relationships among multipole polarizability and many-body dispersion coefficients that arise due to the Gaussian nature of the model. We show that these “combining rules” hold to within a few percent for noble gas atoms, alkali metals, and simple (first-row hydride) molecules such as water; this is consistent with the surprising success that models with underlying Gaussian statistics often exhibit in physics. We present a diagrammatic Jastrow-type perturbation theory tailored to the QDO model that serves to illustrate the rich types of responses that the QDO approach engenders. QDO models for neon, argon, krypton, and xenon, designed to reproduce gas phase properties, are constructed and their condensed phase properties explored via linear scale diffusion Monte Carlo (DMC) and path integral molecular dynamics (PIMD) simulations. Good agreement with experimental data for structure, cohesive energy, and bulk modulus is found, demonstrating a degree of transferability that cannot be achieved using current empirical models or fully ab initio descriptions.

Jones, Andrew P.; Crain, Jason; Sokhan, Vlad P.; Whitfield, Troy W.; Martyna, Glenn J.

2013-04-01

105

NASA Astrophysics Data System (ADS)

The many-body correlation effects in the spatially separated electron and hole layers in the coupled quantum wells are investigated. A special case of the many-component electron-hole system is considered. It is shown that if the hole mass is much greater than the electron mass, the negative correlation energy is mainly determined by the holes. The ground state of the system is found to be the 2D electron-hole liquid with the energy smaller than the exciton phase. It is shown that the system decays into the spatially separated neutral electron-hole drops if the initially created charge density in the layers is smaller than the certain critical value neq.

Babichenko, V. S.; Polishchuk, I. Ya.

2014-11-01

106

Code C# for chaos analysis of relativistic many-body systems

NASA Astrophysics Data System (ADS)

This work presents a new Microsoft Visual C# .NET code library, conceived as a general object oriented solution for chaos analysis of three-dimensional, relativistic many-body systems. In this context, we implemented the Lyapunov exponent and the “fragmentation level” (defined using the graph theory and the Shannon entropy). Inspired by existing studies on billiard nuclear models and clusters of galaxies, we tried to apply the virial theorem for a simplified many-body system composed by nucleons. A possible application of the “virial coefficient” to the stability analysis of chaotic systems is also discussed. Catalogue identifier: AEGH_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGH_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 30?053 No. of bytes in distributed program, including test data, etc.: 801?258 Distribution format: tar.gz Programming language: Visual C# .NET 2005 Computer: PC Operating system: .Net Framework 2.0 running on MS Windows Has the code been vectorized or parallelized?: Each many-body system is simulated on a separate execution thread RAM: 128 Megabytes Classification: 6.2, 6.5 External routines: .Net Framework 2.0 Library Nature of problem: Chaos analysis of three-dimensional, relativistic many-body systems. Solution method: Second order Runge-Kutta algorithm for simulating relativistic many-body systems. Object oriented solution, easy to reuse, extend and customize, in any development environment which accepts .Net assemblies or COM components. Implementation of: Lyapunov exponent, “fragmentation level”, “average system radius”, “virial coefficient”, and energy conservation precision test. Additional comments: Easy copy/paste based deployment method. Running time: Quadratic complexity.

Grossu, I. V.; Besliu, C.; Jipa, Al.; Bordeianu, C. C.; Felea, D.; Stan, E.; Esanu, T.

2010-08-01

107

Object oriented .Net Engine for the Simulation of Three-Dimensional, Relativistic Many-Body Systems

We present an original engine, developed in Microsoft C#.NET, for implementing the simulation of three-dimensional, relativistic many-body systems. Based on the object oriented programming principles and a modern technology, the main goal was to provide both flexibility and a framework which enforces a proper way to reuse and customize the code.

Grossu, I V; Jipa, Al; Felea, D; Bordeianu, C C

2008-01-01

108

Code C# for chaos analysis of relativistic many-body systems with reactions

NASA Astrophysics Data System (ADS)

In this work we present a reaction module for “Chaos Many-Body Engine” (Grossu et al., 2010 [1]). Following our goal of creating a customizable, object oriented code library, the list of all possible reactions, including the corresponding properties (particle types, probability, cross section, particle lifetime, etc.), could be supplied as parameter, using a specific XML input file. Inspired by the Poincaré section, we propose also the “Clusterization Map”, as a new intuitive analysis method of many-body systems. For exemplification, we implemented a numerical toy-model for nuclear relativistic collisions at 4.5 A GeV/c (the SKM200 Collaboration). An encouraging agreement with experimental data was obtained for momentum, energy, rapidity, and angular ? distributions. Catalogue identifier: AEGH_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGH_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 184 628 No. of bytes in distributed program, including test data, etc.: 7 905 425 Distribution format: tar.gz Programming language: Visual C#.NET 2005 Computer: PC Operating system: Net Framework 2.0 running on MS Windows Has the code been vectorized or parallelized?: Each many-body system is simulated on a separate execution thread. One processor used for each many-body system. RAM: 128 Megabytes Classification: 6.2, 6.5 Catalogue identifier of previous version: AEGH_v1_0 Journal reference of previous version: Comput. Phys. Comm. 181 (2010) 1464 External routines: Net Framework 2.0 Library Does the new version supersede the previous version?: Yes Nature of problem: Chaos analysis of three-dimensional, relativistic many-body systems with reactions. Solution method: Second order Runge-Kutta algorithm for simulating relativistic many-body systems with reactions. Object oriented solution, easy to reuse, extend and customize, in any development environment which accepts .Net assemblies or COM components. Treatment of two particles reactions and decays. For each particle, calculation of the time measured in the particle reference frame, according to the instantaneous velocity. Possibility to dynamically add particle properties (spin, isospin, etc.), and reactions/decays, using a specific XML input file. Basic support for Monte Carlo simulations. Implementation of: Lyapunov exponent, “fragmentation level”, “average system radius”, “virial coefficient”, “clusterization map”, and energy conservation precision test. As an example of use, we implemented a toy-model for nuclear relativistic collisions at 4.5 A GeV/c. Reasons for new version: Following our goal of applying chaos theory to nuclear relativistic collisions at 4.5 A GeV/c, we developed a reaction module integrated with the Chaos Many-Body Engine. In the previous version, inheriting the Particle class was the only possibility of implementing more particle properties (spin, isospin, and so on). In the new version, particle properties can be dynamically added using a dictionary object. The application was improved in order to calculate the time measured in the own reference frame of each particle. two particles reactions: a+b?c+d, decays: a?c+d, stimulated decays, more complicated schemas, implemented as various combinations of previous reactions. Following our goal of creating a flexible application, the reactions list, including the corresponding properties (cross sections, particles lifetime, etc.), could be supplied as parameter, using a specific XML configuration file. The simulation output files were modified for systems with reactions, assuring also the backward compatibility. We propose the “Clusterization Map” as a new investigation method of many-body systems. The multi-dimensional Lyapunov Exponent was adapted in order to be used for systems with variable structure. Basic support for Monte Carlo simulations was also added. Additiona

Grossu, I. V.; Besliu, C.; Jipa, Al.; Stan, E.; Esanu, T.; Felea, D.; Bordeianu, C. C.

2012-04-01

109

This thesis involves investigations using the Relativistic Linked-Cluster Many-Body Perturbation Theory (RLCMBPT) procedure to study magnetic hyperfine interactions and electric dipole polarizabilities for several atomic systems. First, the hyperfine fields in the ^ {2}S_{1\\/2} ground state of Ca^{+} and Sr^{+} are studied and the calculated net hyperfine fields are found to have very good agreement with experiments, providing confidence in

Xing Yuan

1995-01-01

110

Code C# for chaos analysis of relativistic many-body systems with reactions

In this work we present a reactions module for "Chaos Many-Body Engine" (Grossu et al., 2010 [1]). Following our goal of creating a customizable, object oriented code library, the list of all possible reactions, including the corresponding properties (particle types, probability, cross-section, particles lifetime etc.), could be supplied as parameter, using a specific XML input file. Inspired by the Poincare section, we propose also the "Clusterization map", as a new intuitive analysis method of many-body systems. For exemplification, we implemented a numerical toy-model for nuclear relativistic collisions at 4.5 A GeV/c (the SKM200 collaboration). An encouraging agreement with experimental data was obtained for momentum, energy, rapidity, and angular {\\pi}- distributions.

I. V. Grossu; C. Besliu; Al. Jipa; E. Stan; T. Esanu; D. Felea; C. C. Bordeianu

2010-09-11

111

Code C# for chaos analysis of relativistic many-body systems with reactions

In this work we present a reactions module for "Chaos Many-Body Engine" (Grossu et al., 2010 [1]). Following our goal of creating a customizable, object oriented code library, the list of all possible reactions, including the corresponding properties (particle types, probability, cross-section, particles lifetime etc.), could be supplied as parameter, using a specific XML input file. Inspired by the Poincare section, we propose also the "Clusterization map", as a new intuitive analysis method of many-body systems. For exemplification, we implemented a numerical toy-model for nuclear relativistic collisions at 4.5 A GeV/c (the SKM200 collaboration). An encouraging agreement with experimental data was obtained for momentum, energy, rapidity, and angular {\\pi}- distributions.

Grossu, I V; Jipa, Al; Stan, E; Esanu, T; Felea, D; Bordeianu, C C

2010-01-01

112

Nuclear quantum many-body dynamics. From collective vibrations to heavy-ion collisions

NASA Astrophysics Data System (ADS)

A summary of recent researches on nuclear dynamics with realistic microscopic quantum approaches is presented. The Balian-Vénéroni variational principle is used to derive the time-dependent Hartree-Fock (TDHF) equation describing the dynamics at the mean-field level, as well as an extension including small-amplitude quantum fluctuations which is equivalent to the time-dependent random-phase approximation (TDRPA). Such formalisms as well as their practical implementation in the nuclear physics framework with modern three-dimensional codes are discussed. Recent applications to nuclear dynamics, from collective vibrations to heavy-ion collisions are presented. Particular attention is devoted to the interplay between collective motions and internal degrees of freedom. For instance, the harmonic nature of collective vibrations is questioned. Nuclei are also known to exhibit superfluidity due to pairing residual interaction. Extensions of the theoretical approach to study such pairing vibrations are now available. Large amplitude collective motions are investigated in the framework of heavy-ion collisions leading, for instance, to the formation of a compound system. How fusion is affected by the internal structure of the collision partners, such as their deformation, is discussed. Other mechanisms in competition with fusion, and responsible for the formation of fragments which differ from the entrance channel (transfer reactions, deep-inelastic collisions, and quasi-fission) are investigated. Finally, studies of actinide collisions forming, during very short times of few zeptoseconds, the heaviest nuclear systems available on Earth, are presented.

Simenel, Cédric

2012-11-01

113

Chaos in fermionic many-body systems and the metal-insulator transition

We show that finite Fermi systems governed by a mean field and a few-body interaction generically possess spectral fluctuations of the Wigner-Dyson type and are, thus, chaotic. Our argument is based on an analogy to the metal-insulator transition. We construct a sparse random-matrix ensemble ScE that mimics that transition. Our claim then follows from the fact that the generic random-matrix ensemble modeling a fermionic interacting many-body system is much less sparse than ScE.

T. Papenbrock; Z. Pluhar; J. Tithof; H. A. Weidenmueller

2009-11-02

114

NASA Astrophysics Data System (ADS)

We propose a new method to calculate ground state position dependent observables in quantum many-body systems. The method, which we call the path-integral diffusion Monte Carlo (PI-DMC) method, is essentially a combination of path-integral Monte Carlo (PIMC) and diffusion Monte Carlo (DMC) methods. The distribution resulting from a DMC simulation is further propagated in imaginary time by PIMC sampling. Tests of the new method for simple cases such as the harmonic oscillator, a double well, and a set of ten coupled harmonic oscillators show that the results for several observables converge rapidly to the exact result.

Hetényi, Balázs; Rabani, Eran; Berne, B. J.

1999-04-01

115

Spectral features of a many-body-localized system weakly coupled to a bath

NASA Astrophysics Data System (ADS)

We study many-body-localized (MBL) systems that are weakly coupled to thermalizing environments, focusing on the spectral functions of local operators. These spectral functions carry signatures of localization even away from the limit of perfectly isolated systems. We find that, in the limit of vanishing coupling to a bath, MBL systems come in two varieties, with either discrete or continuous local spectra. Both varieties of MBL systems exhibit a "soft gap" at zero frequency in the spatially averaged spectral functions of local operators, which serves as a diagnostic for localization. We estimate the degree to which coupling to a bath broadens these spectral features, and we find that some characteristics of incipient localization survive as long as the system-bath coupling is much weaker than the characteristic energy scales of the system. We discuss the crossover to localization that occurs as the coupling to the external bath is tuned to zero. Since perfect isolation is impossible, we expect the ideas discussed in this paper to be relevant for experiments on many-body localization.

Nandkishore, Rahul; Gopalakrishnan, Sarang; Huse, David A.

2014-08-01

116

Charge optimized many-body potential for the Si/SiO{sub 2} system

A dynamic-charge, many-body potential for the Si/SiO{sub 2} system, based on an extended Tersoff potential for semiconductors, is proposed and implemented. The validity of the potential function is tested for both pure silicon and for five polymorphs of silica, for which good agreement is found between the calculated and experimental structural parameters and energies. The dynamic charge transfer intrinsic to the potential function allows the interface properties to be captured automatically, as demonstrated for the silicon/{beta}-cristobalite interface.

Yu Jianguo; Sinnott, Susan B.; Phillpot, Simon R. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611-6400 (United States)

2007-02-15

117

Exponential series expansion for correlation functions of many-body systems

NASA Astrophysics Data System (ADS)

We demonstrate that in Hamiltonian many-body systems at equilibrium, any kind of time dependent correlation function c (t) can always be expanded in a series of (complex) exponential functions of time when its Laplace transform C˜(z) has single poles. The characteristic frequencies can be identified as the eigenfrequencies of the correlation. This is done without introducing the concepts of fluctuating forces and memory functions, due to Mori and Zwanzig and extensively used in the literature in the last decades. Our method is based on a different projection technique in the Hilbert space S of the system and shows that appropriate approximations of the exponential series are related to the contraction of S to a finite, usually small, number of dimensions. The time dependence of correlation functions is always described in detail by a multiple-exponential functionality also at long times. This result is therefore also valid for correlation functions of many-body Hamiltonian systems for which a power-law dependence, observed in restricted time ranges and predicted to be the asymptotic one, can be considered at most as a useful approximate modeling of long-time behavior.

Barocchi, Fabrizio; Guarini, Eleonora; Bafile, Ubaldo

2014-09-01

118

A driven similarity renormalization group approach to quantum many-body problems.

Applications of the similarity renormalization group (SRG) approach [F. Wegner, Ann. Phys. 506, 77 (1994) and S. D. G?azek and K. G. Wilson, Phys. Rev. D 49, 4214 (1994)] to the formulation of useful many-body theories of electron correlation are considered. In addition to presenting a production-level implementation of the SRG based on a single-reference formalism, a novel integral version of the SRG is reported, in which the flow of the Hamiltonian is driven by a source operator. It is shown that this driven SRG (DSRG) produces a Hamiltonian flow that is analogous to that of the SRG. Compared to the SRG, which requires propagating a set of ordinary differential equations, the DSRG is computationally advantageous since it consists of a set of polynomial equations. The equilibrium distances, harmonic vibrational frequencies, and vibrational anharmonicities of a series of diatomic molecules computed with the SRG and DSRG approximated with one- and two-body normal ordered operators are in good agreement with benchmark values from coupled cluster with singles, doubles, and perturbative triples. Particularly surprising results are found when the SRG and DSRG methods are applied to C2 and F2. In the former case, both methods fail to converge, while in the latter case an unbound potential energy curve is obtained. A modified commutator approximation is shown to correct these problems in the case of the DSRG method. PMID:25106572

Evangelista, Francesco A

2014-08-01

119

A driven similarity renormalization group approach to quantum many-body problems

Applications of the similarity renormalization group (SRG) approach [F. Wegner, Ann. Phys. 506, 77 (1994), S. D. G{\\l}azek and K. G. Wilson, Phys. Rev. D 49, 4214 (1994)] to the formulation of useful many-body theories of electron correlation are considered. In addition to presenting a production-level implementation of the SRG based on a single-reference formalism, a novel integral version of the SRG is reported, in which the flow of the Hamiltonian is driven by a source operator. It is shown that this driven SRG (DSRG) produces a Hamiltonian flow that is analogous to that of the SRG. Compared to the SRG, which requires propagating a set of ordinary differential equations, the DSRG is computationally advantageous since it consists of a set of polynomial equations. The equilibrium distances, harmonic vibrational frequencies, and vibrational anharmonicities of a series of diatomic molecules computed with the SRG and DSRG approximated with one- and two-body normal ordered operators are in good agreement with be...

Evangelista, Francesco A

2014-01-01

120

Long-Range Interacting Many-Body Systems with Alkaline-Earth-Metal Atoms

NASA Astrophysics Data System (ADS)

Alkaline-earth-metal atoms can exhibit long-range dipolar interactions, which are generated via the coherent exchange of photons on the P03-D13 transition of the triplet manifold. In the case of bosonic strontium, which we discuss here, this transition has a wavelength of 2.6?m and a dipole moment of 4.03 D, and there exists a magic wavelength permitting the creation of optical lattices that are identical for the states P03 and D13. This interaction enables the realization and study of mixtures of hard-core lattice bosons featuring long-range hopping, with tunable disorder and anisotropy. We derive the many-body master equation, investigate the dynamics of excitation transport, and analyze spectroscopic signatures stemming from coherent long-range interactions and collective dissipation. Our results show that lattice gases of alkaline-earth-metal atoms permit the creation of long-lived collective atomic states and constitute a simple and versatile platform for the exploration of many-body systems with long-range interactions. As such, they represent an alternative to current related efforts employing Rydberg gases, atoms with large magnetic moment, or polar molecules.

Olmos, B.; Yu, D.; Singh, Y.; Schreck, F.; Bongs, K.; Lesanovsky, I.

2013-04-01

121

We address the question to what extent the centre-of-mass (COM) separation can change our view of the many-body problem in quantum chemistry and solid state physics. It was shown that the many-body treatment based on the electron-vibrational Hamiltonian is fundamentally inconsistent with the Born-Handy ansatz so that such a treatment can never respect the COM problem. Born-Oppenheimer (B-O) approximation reveals

Michal Svrcek

2010-01-01

122

Stochastic many-body problems in ecology, evolution, neuroscience, and systems biology

NASA Astrophysics Data System (ADS)

Using the tools of many-body theory, I analyze problems in four different areas of biology dominated by strong fluctuations: The evolutionary history of the genetic code, spatiotemporal pattern formation in ecology, spatiotemporal pattern formation in neuroscience and the robustness of a model circadian rhythm circuit in systems biology. In the first two research chapters, I demonstrate that the genetic code is extremely optimal (in the sense that it manages the effects of point mutations or mistranslations efficiently), more than an order of magnitude beyond what was previously thought. I further show that the structure of the genetic code implies that early proteins were probably only loosely defined. Both the nature of early proteins and the extreme optimality of the genetic code are interpreted in light of recent theory [1] as evidence that the evolution of the genetic code was driven by evolutionary dynamics that were dominated by horizontal gene transfer. I then explore the optimality of a proposed precursor to the genetic code. The results show that the precursor code has only limited optimality, which is interpreted as evidence that the precursor emerged prior to translation, or else never existed. In the next part of the dissertation, I introduce a many-body formalism for reaction-diffusion systems described at the mesoscopic scale with master equations. I first apply this formalism to spatially-extended predator-prey ecosystems, resulting in the prediction that many-body correlations and fluctuations drive population cycles in time, called quasicycles. Most of these results were previously known, but were derived using the system size expansion [2, 3]. I next apply the analytical techniques developed in the study of quasi-cycles to a simple model of Turing patterns in a predator-prey ecosystem. This analysis shows that fluctuations drive the formation of a new kind of spatiotemporal pattern formation that I name "quasi-patterns." These quasi-patterns exist over a much larger range of physically accessible parameters than the patterns predicted in mean field theory and therefore account for the apparent observations in ecology of patterns in regimes where Turing patterns do not occur. I further show that quasi-patterns have statistical properties that allow them to be distinguished empirically from mean field Turing patterns. I next analyze a model of visual cortex in the brain that has striking similarities to the activator-inhibitor model of ecosystem quasi-pattern formation. Through analysis of the resulting phase diagram, I show that the architecture of the neural network in the visual cortex is configured to make the visual cortex robust to unwanted internally generated spatial structure that interferes with normal visual function. I also predict that some geometric visual hallucinations are quasi-patterns and that the visual cortex supports a new phase of spatially scale invariant behavior present far from criticality. In the final chapter, I explore the effects of fluctuations on cycles in systems biology, specifically the pervasive phenomenon of circadian rhythms. By exploring the behavior of a generic stochastic model of circadian rhythms, I show that the circadian rhythm circuit exploits leaky mRNA production to safeguard the cycle from failure. I also show that this safeguard mechanism is highly robust to changes in the rate of leaky mRNA production. Finally, I explore the failure of the deterministic model in two different contexts, one where the deterministic model predicts cycles where they do not exist, and another context in which cycles are not predicted by the deterministic model.

Butler, Thomas C.

123

Entropy production and wave packet dynamics in the Fock space of closed chaotic many-body systems

NASA Astrophysics Data System (ADS)

Highly excited many-particle states in quantum systems such as nuclei, atoms, quantum dots, spin systems, quantum computers, etc., can be considered as ``chaotic'' superpositions of mean-field basis states (Slater determinants, products of spin or qubit states). This is due to a very high level density of many-body states that are easily mixed by a residual interaction between particles (quasiparticles). For such systems, we have derived simple analytical expressions for the time dependence of the energy width of wave packets, as well as for the entropy, number of principal basis components, and inverse participation ratio, and tested them in numerical experiments. It is shown that the energy width ?(t) increases linearly and very quickly saturates. The entropy of a system increases quadratically, S(t)~t2, at small times, and afterward can grow linearly, S(t)~t, before saturation. Correspondingly, the number of principal components determined by the entropy Npc~exp[S(t)] or by the inverse participation ratio increases exponentially fast before saturation. These results are explained in terms of a cascade model which describes the flow of excitation in the Fock space of basis components. Finally, the striking phenomenon of damped oscillations in the Fock space at the transition to equilibrium is discussed.

Flambaum, V. V.; Izrailev, F. M.

2001-09-01

124

Transition pathways in a many-body system: Application to hydrogen-bond breaking in water

We apply a stochastic method introduced by Dellago {ital et al.} [J. Chem. Phys. {bold 108}, 1964 (1998)] to sample transition paths in high-dimensional systems. The method connects two endpoint regions (for example a reactant and a product region) by a set of space-time paths. This approach is an importance sampling for rare events that does not require prior knowledge of the location of dynamical bottlenecks. Transition paths are generated with a weight corresponding to a chain of Metropolis Monte Carlo steps. We derive Monte Carlo algorithms and apply the technique to the dynamics of hydrogen-bond breaking in liquid water. We obtain averages in a transition path ensemble for the structure and energy along the trajectory. While characterized by a rate constant, hydrogen-bond breaking in water occurs frequently enough to be studied by standard methods. The process therefore provides a useful test of path sampling methods. The comparison between path sampling and standard Monte Carlo demonstrate the feasibility of transition path sampling for a many-body system with a rough potential energy surface. {copyright} {ital 1998 American Institute of Physics.}

Csajka, F.S.; Chandler, D. [Department of Chemistry, University of California at Berkeley, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California at Berkeley, Berkeley, California 94720 (United States)

1998-07-01

125

Gauge Equivalence among Quantum Nonlinear Many Body Systems

Transformations performing on the dependent and\\/or the independent variables are an useful method used to classify PDE in\\u000a class of equivalence. In this paper we consider a large class of U(1)-invariant nonlinear Schrödinger equations containing\\u000a complex nonlinearities. The U(1) symmetry implies the existence of a continuity equation for the particle density ??|?|2 where the current j\\u000a \\u000a ?\\u000a has, in general,

Antonio M. Scarfone

2008-01-01

126

IASSNS-HEP-91/23 Many-body Systems with Non-Abelian Statistics *

field theory to construct many-body Hamiltoni- ans whose ground states support quasiparticle excitations. We discuss the calculation of the quasiparticle statistics from the low energy effective theory(k) level N CS theory, and the charge e/k quasiparticles were shown to carry the non-abelian statistics

Wen, Xiao-Gang

127

NASA Astrophysics Data System (ADS)

A simple approach is discussed which associates to (solvable) matrix equations (solvable) dynamical systems, generally interpretable as (interesting) many-body problems, possibly involving auxiliary dependent variables in addition to those identifying the positions of the moving particles. We then focus on cases in which the auxiliary variables can be altogether eliminated, reobtaining thereby (via this unified approach) well-known solvable many-body problems, and moreover a (solvable) extension of the "goldfish" model.

Calogero, Francesco

2004-06-01

128

The following issues are discussed inspired by the recent paper of Kadanoff (arXiv: 1403:6162): (a) Construction of a generalized one-particle Wigner distribution (GWD) function (analog of the classical distribution function) from which the quantum kinetic equation due to Kadanoff and Baym (KB) is derived, often called the Quantum Boltzmann Equation (QBE); (b) The equation obeyed by this has a collision contribution in the form of a two-particle Green function. This term is manipulated to have Kinetic Entropy in parallel to its counterpart in the classical Boltzmann kinetic equation for the classical distribution function. This proved to be problematic in that unlike in the classical Boltzmann kinetic equation, the contribution from the kinetic entropy term was non-positive; (3) Kadanoff surmised that this situation could perhaps be related to quantum entanglement that may not have been included in his theory. It is shown that GWD is not positive everywhere (indicating dynamical quantumness) just like the commonly recognized property of the Wigner function (negative property indicating quantumness of the state). The issue of non-positive feature appearing in approximate evaluation of patently positive entities in many particle systems is here pointed to an early discussion of this issue (Phys. Rev. A10, 1852 (1974)) in terms of a theorem on truncation of cumulant expansion of a probability distribution function due to Marcinkeiwicz. The last issue of presence or absence of entanglement in an approximate evaluation of a many particle correlation poses a new problem; it is considered here in terms of fermionic entanglement theory in the light of density matrix and Green function theory of many-fermion systems. The clue comes from the fact that the Hartree-Fock approximation exhbits no entantanglement in two-particle fermion density matrix and hence also in two-particle Green function.

A. K. Rajgaopal

2014-05-12

129

Physics 832: Quantum Many-Body Physics Fall 2011 Lecture: TuTh 2:00Â3:15 in Phy 2202 by Michael Levin (Office: Phy 2220). Prerequisites: Quantum mechanics (Physics 402), Statistical physics (Physics, and the renormalization group, I will discuss some modern topics in quantum condensed matter physics, including (hopefully

Lathrop, Daniel P.

130

Simulating many-body lattice systems on a single nano-mechanical resonator

We show that lattice systems, such as the Bose-Hubbard model, can be simulated on a single nano- or micro-mechanical resonator, by exploiting its many modes. The on-site Hamiltonians are engineered by coupling the mechanical modes to the modes of a pair of optical or stripline resonators, and the connections between the lattice sites are engineered in a similar way. The lattice network structure is encoded in the frequency components of the fields driving the resonators. This three-resonator configuration also allows universal quantum computing on the nano-resonator.

Kurt Jacobs

2012-09-12

131

The coupled-cluster approach to quantum many-body problem in a three-Hilbert-space reinterpretation

The quantum many-body bound-state problem in its computationally successful coupled cluster method (CCM) representation is reconsidered. In conventional practice one factorizes the ground-state wave functions $|\\Psi\\rangle= e^S |\\Phi\\rangle$ which live in the "physical" Hilbert space ${\\cal H}^{(P)}$ using an elementary ansatz for $|\\Phi\\rangle$ plus a formal expansion of $S$ in an operator basis of multi-configurational creation operators. In our paper a reinterpretation of the method is proposed. Using parallels between the CCM and the so called quasi-Hermitian, alias three-Hilbert-space (THS), quantum mechanics, the CCM transition from the known microscopic Hamiltonian (denoted by usual symbol $H$), which is self-adjoint in ${\\cal H}^{(P)}$, to its effective lower-case isospectral avatar $\\hat{h}=e^{-S} H e^S$, is assigned a THS interpretation. In the opposite direction, a THS-prescribed, non-CCM, innovative reinstallation of Hermiticity is shown to be possible for the CCM effective Hamiltonian $\\hat{h}$, which only appears manifestly non-Hermitian in its own ("friendly") Hilbert space ${\\cal H}^{(F)}$. This goal is achieved via an ad hoc amendment of the inner product in ${\\cal H}^{(F)}$, thereby yielding the third ("standard") Hilbert space ${\\cal H}^{(S)}$. Due to the resulting exact unitary equivalence between the first and third spaces, ${\\cal H}^{(P)}\\sim {\\cal H}^{(S)}$, the indistinguishability of predictions calculated in these alternative physical frameworks is guaranteed.

Raymond F. Bishop; Miloslav Znojil

2013-11-25

132

The (Berry-Aharonov-Anandan) geometric phase acquired during a cyclic quantum evolution of finite-dimensional quantum systems is studied. It is shown that a pure quantum state in a (2J+1)-dimensional Hilbert space (or, equivalently, of a spin-J system) can be mapped onto the partition function of a gas of independent Dirac strings moving on a sphere and subject to the Coulomb repulsion of 2J fixed test charges (the Majorana stars) characterizing the quantum state. The geometric phase may be viewed as the Aharonov-Bohm phase acquired by the Majorana stars as they move through the gas of Dirac strings. Expressions for the geometric connection and curvature, for the metric tensor, as well as for the multipole moments (dipole, quadrupole, etc.), are given in terms of the Majorana stars. Finally, the geometric formulation of the quantum dynamics is presented and its application to systems with exotic ordering such as spin nematics is outlined. PMID:23004240

Bruno, Patrick

2012-06-15

133

Ultra-cold atomic matter and quantum information My group studies various many-body states of ultra cold atoms and investigates possible applications towards quantum computation. Two subjects studies of nematic Mott states and dimerized valence bond states of spin-one atoms. We also have

Plotkin, Steven S.

134

The Relativistic Linked-Cluster Many-Body Perturbation Theory (RLCMBPT) technique has been successfully applied to the study of the magnetic dipole hyperfine interaction in a variety of atomic and ionic systems. The RLCMBPT procedure has produced theoretical results which agree well with those experimental results which are available. In addition, the RLCMBPT method makes it possible to calculate the contributions to the

Randy Wade Dougherty

1991-01-01

135

NASA Astrophysics Data System (ADS)

Recent experimental achievements in controlling ultracold gases in optical lattices open a new perspective on quantum many-body physics. In these experimental setups, it is possible to study coherent time evolution of isolated quantum systems. These dynamics reveal new physics beyond the low-energy properties that are usually relevant in solid-state many-body systems. In this paper, we study the time evolution of antiferromagnetic order in the Heisenberg chain after a sudden change of the anisotropy parameter, using various numerical and analytical methods. As a generic result, we find that the order parameter, which can show oscillatory or non-oscillatory dynamics, decays exponentially except for the effectively non-interacting case of the XX limit. For weakly ordered initial states, we also find evidence for an algebraic correction to the exponential law. The study is based on numerical simulations using a numerical matrix product method for infinite system sizes (iMPS), for which we provide a detailed description and an error analysis. Additionally, we investigate in detail the exactly solvable XX limit. These results are compared to approximative analytical approaches including an effective description by the XZ model as well as by mean-field, Luttinger-liquid and sine-Gordon theories. The comparison reveals which aspects of non-equilibrium dynamics can, as in equilibrium, be described by low-energy theories and which are the novel phenomena specific to quantum quench dynamics. The relevance of the energetically high part of the spectrum is illustrated by means of a full numerical diagonalization of the Hamiltonian.

Barmettler, Peter; Punk, Matthias; Gritsev, Vladimir; Demler, Eugene; Altman, Ehud

2010-05-01

136

Many-body energies during proton transfer in an aqueous system.

The energetics of the mechanism of proton transfer from a hydronium ion to one of the water molecules in its first solvation shell are studied using density functional theory and the Møller-Plesset perturbation (MP2) method. The potential energy surface of the proton transfer mechanism is obtained at the B3LYP and MP2 levels with the 6-311++G** basis set. Many-body analysis is applied to the proton transfer mechanism to obtain the change in relaxation energy, two-body, three-body and four-body energies when proton transfer occurs from the hydronium ion to one of the water molecules in its first solvation shell. It is observed that the binding energy (BE) of the complex decreases during the proton transfer process at both levels of theory. During the proton transfer process, the % contribution of the total two-body energy to the binding energy of the complex increases from 62.9 to 68.09% (39.9 to 45.95%), and that of the total three-body increases from 25.9 to 27.09% (24.16 to 26.17%) at the B3LYP/6-311++G** (MP2/ 6-311++G**) level. There is almost no change in the water-water-water three-body interaction energy during the proton transfer process at both levels of theory. The contribution of the relaxation energy and the total four-body energy to the binding energy of the complex is greater at the MP2 level than at the B3LYP level. Significant differences are found between the relaxation energies, the hydronium-water interaction energies and the four-body interaction energies at the B3LYP and MP2 levels. PMID:20195664

Chaudhari, Ajay; Meraj, Gul Afroz; Lee, Shyi-Long

2010-10-01

137

Many-body effects in electron spin resonance in 2D systems with Rashba spin-orbit interaction

NASA Astrophysics Data System (ADS)

We report effects of electron-electron (e-e) interaction on electron spin resonance (ESR) in two-dimensional (2D) systems with Rashba spin-orbit interaction (SOI). Using the Hartree-Fock approximation, we demonstrate that Rashba SOI results in non-zero many-body corrections to the ESR energy. We discover that e-e interaction in 2D systems with SOI can not only enhance the ESR energy but also lead to the ESR energy reduction. The magnitude of this effect exhibits remarkable features in a wide range of parameters relevant to experiment: it is found to be rather sensitive to the sign of g-factor and the filling factor of Landau levels ?. We derive analytical expressions for many-body corrections to ESR energy and energy dispersion of spin wave excitations for the case of \

Krishtopenko, S. S.

2014-06-01

138

NASA Astrophysics Data System (ADS)

We take advantage of the simple approach, recently discussed, which associates to (solvable) matrix equations (solvable) dynamical systems interpretable as (interesting) many-body problems, possibly involving auxiliary dependent variables in addition to those identifying the positions of the moving particles. Starting from a solvable matrix evolution equation, we obtain the corresponding many-body model and note that in one case the auxiliary variables can be altogether eliminated, obtaining thereby an (also Hamiltonian) extension of the "goldfish" model. The solvability of this novel model, and of its isochronous variant, is exhibited. A related, as well solvable, model, is also introduced, as well as its isochronous variant. Finally, the small oscillations of the isochronous models around their equilibrium configurations are investigated, and from their isochronicity certain diophantine relations are evinced.

Calogero, Francesco

2004-12-01

139

January 2014) For classical Brownian systems driven out of equilibrium, we derive inhomogeneous two for the development of approximation schemes. The rules of functional calculus lead naturally to non-Markovian-body systems Joseph M. Brader1,a) and Matthias Schmidt2,b) 1 Soft Matter Theory, University of Fribourg, CH

Schmidt, Matthias

140

a Solvable Model of Interacting Many Body Systems Exhibiting a Breakdown of the Boltzmann Equation

NASA Astrophysics Data System (ADS)

In a particular exactly solvable model of an interacting system, the Boltzmann equation predicts a constant single particle density operator, whereas the exact solution gives a single particle density operator with a nontrivial time dependence. All of the time dependence of the single particle density operator is generated by the correlations.

McKellar, B. H. J.

2014-12-01

141

Detecting two-site spin-entanglement in many-body systems with local particle-number fluctuations

We derive experimentally measurable lower bounds for the two-site entanglement of the spin-degrees of freedom of many-body systems with local particle-number fluctuations. Our method aims at enabling the spatially resolved detection of spin-entanglement in Hubbard systems using high-resolution imaging in optical lattices. A possible application is the observation of entanglement generation and spreading during spin impurity dynamics, for which we provide numerical simulations. More generally, the scheme can simplify the entanglement detection in ion chains, Rydberg atoms, or similar atomic systems.

Leonardo Mazza; Davide Rossini; Rosario Fazio; Manuel Endres

2014-08-20

142

Influence of the interaction range on the thermostatistics of a classical many-body system

NASA Astrophysics Data System (ADS)

We numerically study a one-dimensional system of N classical localized planar rotators coupled through interactions which decay with distance as 1/r? (??0). The approach is a first principle one (i.e., based on Newton’s law), and yields the probability distribution of momenta. For ? large enough and N?1 we observe, for longstanding states, the Maxwellian distribution, landmark of Boltzmann-Gibbs thermostatistics. But, for ? small or comparable to unity, we observe instead robust fat-tailed distributions that are quite well fitted with q-Gaussians. These distributions extremize, under appropriate simple constraints, the nonadditive entropy Sq upon which nonextensive statistical mechanics is based. The whole scenario appears to be consistent with nonergodicity and with the thesis of the q-generalized Central Limit Theorem.

Cirto, Leonardo J. L.; Assis, Vladimir R. V.; Tsallis, Constantino

2014-01-01

143

Relativistic nuclear many-body theory

Nonrelativistic models of nuclear systems have provided important insight into nuclear physics. In future experiments, nuclear systems will be examined under extreme conditions of density and temperature, and their response will be probed at momentum and energy transfers larger than the nucleon mass. It is therefore essential to develop reliable models that go beyond the traditional nonrelativistic many-body framework. General properties of physics, such as quantum mechanics, Lorentz covariance, and microscopic causality, motivate the use of quantum field theories to describe the interacting, relativistic, nuclear many-body system. Renormalizable models based on hadronic degrees of freedom (quantum hadrodynamics) are presented, and the assumptions underlying this framework are discussed. Some applications and successes of quantum hadrodynamics are described, with an emphasis on the new features arising from relativity. Examples include the nuclear equation of state, the shell model, nucleon-nucleus scattering, and the inclusion of zero-point vacuum corrections. Current issues and problems are also considered, such as the construction of improved approximations, the full role of the quantum vacuum, and the relationship between quantum hadrodynamics and quantum chromodynamics. We also speculate on future developments. 103 refs., 18 figs.

Serot, B.D. (Indiana Univ., Bloomington, IN (United States)); Walecka, J.D. (Southeastern Universities Research Association, Newport News, VA (United States). Continuous Electron Beam Accelerator Facility)

1991-09-11

144

arXiv:math-ph/9907016v121Jul1999 The Lanczos Algorithm for extensive Many-Body Systems in the

to a review of the applications of this method[1] in strongly correlated electron problems. In this work wearXiv:math-ph/9907016v121Jul1999 UMP-98/? The Lanczos Algorithm for extensive Many-Body Systems rigourously the scaling properties of the Lanczos process applied to an arbitrary extensive Many-Body System

Witte, Nicholas

145

In this letter we report the singlet ground state structure of the full carotenoid peridinin by means of variational Monte Carlo (VMC) calculations. The VMC relaxed geometry has an average bond length alternation of 0.1165(10) {\\AA}, larger than the values obtained by DFT (PBE, B3LYP and CAM-B3LYP) and shorter than that calculated at the Hartree-Fock (HF) level. TDDFT and EOM-CCSD calculations on a reduced peridinin model confirm the HOMO-LUMO major contribution of the Bu+-like (S2) bright excited state. Many Body Green's Function Theory (MBGFT) calculations of the vertical excitation energy of the Bu+-like state for the VMC structure (VMC/MBGFT) provide excitation energy of 2.62 eV, in agreement with experimental results in n-hexane (2.72 eV). The dependence of the excitation energy on the bond length alternation in the MBGFT and TDDFT calculations with different functionals is discussed.

Coccia, Emanuele; Guidoni, Leonardo

2014-01-01

146

A charge-optimized many-body potential for the U-UO2-O2 system.

Building on previous charge-optimized many-body (COMB) potentials for metallic ?-U and gaseous O2, we have developed a new potential for UO2, which also allows the simulation of U-UO2-O2 systems. The UO2 lattice parameter, elastic constants and formation energies of stoichiometric and non-stoichiometric intrinsic defects are well reproduced. Moreover, this is the first rigid-ion potential that produces the correct deviation of the Cauchy relation, as well as the first classical interatomic potential that is able to determine the defect energies of non-stoichiometric intrinsic point defects in UO2 with an appropriate reference state. The oxygen molecule interstitial in the ?-U structure is shown to decompose, with some U-O bonds approaching the natural bond length of perfect UO2. Finally, we demonstrate the capability of this COMB potential to simulate a complex system by performing a simulation of the ?-U + O2 ? UO2 phase transformation. We also identify a possible mechanism for uranium oxidation and the orientation of the resulting fluorite UO2 structure relative to the coordinate system of orthorhombic ?-U. PMID:24275484

Li, Yangzhong; Liang, Tao; Sinnott, Susan B; Phillpot, Simon R

2013-12-18

147

NASA Astrophysics Data System (ADS)

In this paper, we discuss the regularities of average energies with a fixed angular momentum I (denoted as EI’s) in many-body systems interacting via a two-body random ensemble. It is found that EI’s with I˜Imin (minimum of I) or I˜Imax (maximum of I) have large probabilities [denoted as P(I)] to be the smallest in energy, and P(I) is close to zero elsewhere. A simple argument assuming the randomness of the two-particle coefficients of fractional parentage is given to explain these observations. A compact trajectory of the energy EI vs I(I+1) is found to be robust. Other regularities, such that there are two or three sizable P(I)’s with I˜Imin but P(I)?P(Imax)’s with I˜Imax, and that the coefficients C defined by

Zhao, Y. M.; Arima, A.; Yoshinaga, N.

2002-12-01

148

NASA Astrophysics Data System (ADS)

Inter-cellular communication is essential for coordinated cell movement and spatio-temporal differentiation. Examples are collective behavior of unicellular organisms (such as Dictyostelium aggregation) and formation of structures in multi-cellular organisms (e.g. gastrulation in early embryos). Cells communicate with one another via short-range contact interactions and long-range interactions mediated by chemical signaling fields. In the examples given above the number of cells varies between hundreds to tens of thousands, and the cell population may have strong phenotypic heterogeneity. It is therefore important to develop a model framework which retains discrete cell identity, and allows a flexible description of cell-cell interactions. We present one such framework here, inspired by the many-body formulation of interacting systems, and constructed using approximations which are biologically plausible. We describe a perturbative analysis of chemotactic aggregation, which illustrates the importance of statistical correlations between cells. We also discuss the implementation of this framework as an optimized numerical algorithm, and show some early results on primitive streak formation in the chick embryo.

Newman, Timothy

2005-03-01

149

We propose that it might be possible to determine the contribution of many-body interactions to the large effective mass in ''heavy-fermion'' materials, e.g., UPt/sub 3/, by the method of conduction-electron-spin resonance (CESR). A microwave transmission observation of CESR may show a resonance pattern which, based on already measured parameters, would clearly distinguish among suggested models.

Bedell, K.S.; Meltzer, D.E.

1985-08-01

150

Shaul Mukamel,2 and Steven T. Cundiff1, 1 JILA, National Institute of Standards and Technology, Irvine, California, 92697-2025, USA 3 National Institute of Standards and Technology, Boulder, Colorado. A hallmark of many-body interactions has been the appearance of a signal for negative delay in two

Mukamel, Shaul

151

Given a quantum many-body system, the Self-Consistent Phonons (SCP) method provides an optimal harmonic approximation by minimizing the free energy. In particular, the SCP estimate for the vibrational ground state (zero temperature) appears to be surprisingly accurate. We explore the possibility of going beyond the SCP approximation by considering the system Hamiltonian evaluated in the harmonic eigenbasis of the SCP Hamiltonian. It appears that the SCP ground state is already uncoupled to all singly- and doubly-excited basis functions. So, in order to improve the SCP result at least triply-excited states must be included, which then reduces the error in the ground state estimate substantially. For a multidimensional system two numerical challenges arise, namely, evaluation of the potential energy matrix elements in the harmonic basis, and handling and diagonalizing the resulting Hamiltonian matrix, whose size grows rapidly with the dimensionality of the system. Using the example of water hexamer we demonstrate that such calculation is feasible, i.e., constructing and diagonalizing the Hamiltonian matrix in a triply-excited SCP basis, without any additional assumptions or approximations. Our results indicate particularly that the ground state energy differences between different isomers (e.g., cage and prism) of water hexamer are already quite accurate within the SCP approximation.

Georgescu, Ionu?, E-mail: ionutg@gmail.com; Mandelshtam, Vladimir A. [Chemistry Department, University of California, Irvine, California 92697 (United States)] [Chemistry Department, University of California, Irvine, California 92697 (United States); Jitomirskaya, Svetlana [Department of Mathematics, University of California, Irvine, California 92697 (United States)] [Department of Mathematics, University of California, Irvine, California 92697 (United States)

2013-11-28

152

Many-Body Localization: Concepts and Simple Models

We review recent results on many-body localization for two explicitly analyzable models of many-body quantum systems, the XY spin chain in transversal magnetic field as well as interacting systems of harmonic quantum oscillators. In both models the presence of disorder leads to dynamical localization in the form of zero-velocity Lieb-Robinson bounds and to exponential decay of ground state correlations. Moreover, for oscillator systems one can also show exponential decay of thermal states as well as an area law bound for the entanglement entropy of ground and thermal states. The key fact which allows a rigorous analysis of these models is that they are given by many-body Hamiltonians which can be reduced to effective single particle Hamiltonians.

Robert Sims; Gunter Stolz

2013-12-02

153

Nuclear Many-Body Physics Where Structure And Reactions Meet

The path from understanding a simple reaction problem of scattering or tunneling to contemplating the quantum nuclear many-body system, where structure and continuum of reaction-states meet, overlap and coexist, is a complex and nontrivial one. In this presentation we discuss some of the intriguing aspects of this route.

Naureen Ahsan; Alexander Volya

2009-06-24

154

Interferometric Probes of Many-Body Localization

We propose a method for detecting many-body localization (MBL) in disordered spin systems. The method involves pulsed coherent spin manipulations that probe the dephasing of a given spin due to its entanglement with a set ...

Knap, M.

155

Penn State: Consortium for Education in Many-Body Applications

NSDL National Science Digital Library

Funded by the National Science Foundation, the Consortium for Education in Many-Body Applications at Penn State University brings together scientists from a range of scientific and engineering disciplines to address "many-body" problems. These problems refer to "the complexities that arise when more than a few electrons or atoms or particles are involved." The solutions involve "the use of high performance and massively parallel computers coupled with improved algorithms." Drawing from seven academic departments (Aerospace Engineering, Chemistry, Chemical Engineering, Computer Science and Engineering, Materials Science and Engineering, Mathematics, and Physics) they offer courses, summer internships, seminars and tutorials, and conduct research projects. The Research section of the website provides summary articles on a variety of topics, including High-Performance and Parallel Computing; Advanced Visualization; and Quantum mechanics of many-body systems. Descriptions of courses and seminars as well as some of the PowerPoint presentations are also available online.

156

We study the nearest-neighbor distributions of the k -body embedded ensembles of random matrices for n bosons distributed over two-degenerate single-particle states. This ensemble, as a function of k , displays a transition from harmonic-oscillator behavior (k=1) to random-matrix-type behavior (k=n) . We show that a large and robust quasidegeneracy is present for a wide interval of values of k when the ensemble is time-reversal invariant. These quasidegenerate levels are Shnirelman doublets which appear due to the integrability and time-reversal invariance of the underlying classical systems. We present results related to the frequency in the spectrum of these degenerate levels in terms of k and discuss the statistical properties of the splittings of these doublets. PMID:20365843

Hernández-Quiroz, Saúl; Benet, Luis

2010-03-01

157

We show the coherent control of dephasing process of exciton polarization due to heavy hole-heavy hole and heavy hole-light hole scatterings in a GaAs single quantum well. The memory time of the exction scattering is estimated as 0.47 ps.

Ogawa, Y.; Minami, F. [Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan)

2013-12-04

158

Many-body wave function in a dipole blockade configuration

We report the results of simulations of the many atom wave function when a cold gas is excited to highly excited states. We simulated the many body wave function by direct numerical solution of Schroedinger's equation. We investigated the fraction of atoms excited and the correlation of excited atoms in the gas for different types of excitation when the blockade region was small compared to the sample size. We also investigated the blockade effect when the blockade region is comparable to the sample size to determine the sensitivity of this system and constraints for quantum information.

Robicheaux, F.; Hernandez, J. V. [Department of Physics, Auburn University, Alabama 36849-5311 (United States)

2005-12-15

159

A review on recent applications of the sequential quantum Mechanics\\/Molecular mechanics (QM\\/MM) methodology to the study of the electronic properties of hydrogen bond systems is presented. Results for the absorption spectra of water clusters and liquid water, ionization of liquid water and ammonia, charge transfer to solvent in halide aqueous solution, and solvatochromic shifts of small organic molecules in water

Ricardo A. Mata; B. J. Costa Cabral

2010-01-01

160

The self-healing diffusion Monte Carlo algorithm (SHDMC) [Reboredo, Hood and Kent, Phys. Rev. B {\\bf 79}, 195117 (2009); Reboredo, {\\it ibid.} {\\bf 80}, 125110 (2009)] is extended to study the ground and excited states of magnetic and periodic systems. The method converges to exact eigenstates as the statistical data collected increases if the wave function is sufficiently flexible. It is shown that the wave functions of complex anti-symmetric eigen-states can be written as the product of an anti-symmetric real factor and a symmetric phase factor. The dimensionality of the nodal surface is dependent on whether phase is a scalar function or not. A recursive optimization algorithm is derived from the time evolution of the mixed probability density, which is given by an ensemble of electronic configurations (walkers) with complex weight. This complex weight allows the amplitude of the fixed-node wave function to move away from the trial wave function phase. This novel approach is both a generalization of SHDMC and the fixed-phase approximation [Ortiz, Ceperley and Martin, Phys Rev. Lett. {\\bf 71}, 2777 (1993)]. When used recursively it simultaneously improves the node and the phase. The algorithm is demonstrated to converge to nearly exact solutions of model systems with periodic boundary conditions or applied magnetic fields. The computational cost is proportional to the number of independent degrees of freedom of the phase. The method is applied to obtain low-energy excitations of Hamiltonians with magnetic field or periodic boundary conditions. The method is used to optimize wave functions with twisted boundary conditions, which are included in a many-body Bloch phase. The potential applications of this new method to study periodic, magnetic, and complex Hamiltonians are discussed.

Fernando Agustín Reboredo

2010-07-19

161

NASA Astrophysics Data System (ADS)

The self-healing diffusion Monte Carlo algorithm (SHDMC) [F. A. Reboredo, R. Q. Hood, and P. R. C. Kent, Phys. Rev. B 79, 195117 (2009); F. A. Reboredo, ibid. 80, 125110 (2009)] is extended to study the ground and excited states of magnetic and periodic systems. The method converges to exact eigenstates as the statistical data collected increase if the wave function is sufficiently flexible. It is shown that the dimensionality of the nodal surface is dependent on whether phase is a scalar function or not. A recursive optimization algorithm is derived from the time evolution of the mixed probability density, which is given by an ensemble of electronic configurations (walkers) with complex weight. This complex weight allows the phase of the fixed-node wave function to move away from the trial wave function phase. This novel approach is both a generalization of SHDMC and the fixed-phase approximation [G. Ortiz, D. M. Ceperley, and R. M. Martin, Phys Rev. Lett. 71, 2777 (1993)]. When used recursively it simultaneously improves the node and the phase. The algorithm is demonstrated to converge to nearly exact solutions of model systems with periodic boundary conditions or applied magnetic fields. The computational cost is proportional to the number of independent degrees of freedom of the phase. The method is applied to obtain low-energy excitations of Hamiltonians with magnetic field. Periodic boundary conditions are also considered optimizing wave functions with twisted boundary conditions which are included in a many-body Bloch phase. The potential applications of this new method to study periodic, magnetic, and complex Hamiltonians are discussed.

Reboredo, Fernando Agustín

2012-05-01

162

Introducing many-body physics using atomic spectroscopy

NASA Astrophysics Data System (ADS)

Atoms constitute relatively simple many-body systems, making them suitable objects for developing an understanding of basic aspects of many-body physics. Photoabsorption spectroscopy is a prominent method to study the electronic structure of atoms and the inherent many-body interactions. In this article, the impact of many-body effects on well-known spectroscopic features, such as Rydberg series, Fano resonances, Cooper minima, and giant resonances, is studied and related many-body phenomena in other fields are outlined. To calculate photoabsorption cross sections, the time-dependent configuration interaction singles (TDCIS) model is employed. The conceptual clearness of TDCIS in combination with the compactness of atomic systems allows for a pedagogical introduction to many-body phenomena.

Krebs, Dietrich; Pabst, Stefan; Santra, Robin

2014-02-01

163

Emergence of stationary many-body entanglement in driven-dissipative Rydberg lattice gases

Non-equilibrium quantum dynamics represents an emerging paradigm for condensed matter physics, quantum information science, and statistical mechanics. Strongly interacting Rydberg atoms offer an attractive platform to study driven-dissipative dynamics of quantum spin models with long-range order. Here, we explore the conditions under which stationary many-body entanglement persists with near-unit fidelity and high scalability. In our approach, coherent many-body dynamics is driven by Rydberg-mediated laser transitions, while atoms at the lattice boundary reduce the entropy of the many-body state. Surprisingly, the many-body entanglement is established by continuously evolving a locally dissipative Rydberg system towards the steady-state, as with optical pumping. We characterize the dynamics of multipartite entanglement in a 1D lattice by way of quantum uncertainty relations, and demonstrate the long-range behavior of the stationary entanglement with finite-size scaling, reaching "hectapartite" entanglement under experimental conditions. Our work opens a route towards dissipative preparation of many-body entanglement with unprecedented scaling behavior.

S. K. Lee; J. Cho; K. S. Choi

2013-12-30

164

On the Neutrino Self Refraction Problem from a Many-Body Perspective

We consider a dense neutrino gas as a many body system by taking into account both vacuum oscillations and self interactions of neutrinos. We show that the exact many body Hamiltonian which describes the flavor oscillations of such a dense neutrino gas has many constants of motion whose eigenvalues represent a set of good quantum numbers. However, if one adopts the random phase approximation as an effective one particle description, these operators are no longer conserved (i.e. they cease to represent good quantum numbers) although their expectation values are still conserved.

Pehlivan, Y. [Mimar Sinan Fine Arts University Besiktas, Istanbul 34349 (Turkey); National Astronomical Observatory of Japan 2-21-1 Osawa, Mitaka Tokyo, 181-8588 (Japan); Kajino, Toshitaka [National Astronomical Observatory of Japan 2-21-1 Osawa, Mitaka Tokyo, 181-8588 (Japan); Department of Astronomy, Graduate School of Science, University of Tokyo, Tokyo 113-0033 (Japan); Balantekin, A. B. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Yoshida, Takashi [Department of Astronomy, Graduate School of Science, University of Tokyo, Tokyo 113-0033 (Japan); Maruyama, Tomoyuki [College of Bioresource Sciences, Nihon University, Fujisawa 252-8510 (Japan)

2010-08-12

165

Interferometric probes of many-body localization.

We propose a method for detecting many-body localization (MBL) in disordered spin systems. The method involves pulsed coherent spin manipulations that probe the dephasing of a given spin due to its entanglement with a set of distant spins. It allows one to distinguish the MBL phase from a noninteracting localized phase and a delocalized phase. In particular, we show that for a properly chosen pulse sequence the MBL phase exhibits a characteristic power-law decay reflecting its slow growth of entanglement. We find that this power-law decay is robust with respect to thermal and disorder averaging, provide numerical simulations supporting our results, and discuss possible experimental realizations in solid-state and cold-atom systems. PMID:25325656

Serbyn, M; Knap, M; Gopalakrishnan, S; Papi?, Z; Yao, N Y; Laumann, C R; Abanin, D A; Lukin, M D; Demler, E A

2014-10-01

166

Interferometric Probes of Many-Body Localization

NASA Astrophysics Data System (ADS)

We propose a method for detecting many-body localization (MBL) in disordered spin systems. The method involves pulsed coherent spin manipulations that probe the dephasing of a given spin due to its entanglement with a set of distant spins. It allows one to distinguish the MBL phase from a noninteracting localized phase and a delocalized phase. In particular, we show that for a properly chosen pulse sequence the MBL phase exhibits a characteristic power-law decay reflecting its slow growth of entanglement. We find that this power-law decay is robust with respect to thermal and disorder averaging, provide numerical simulations supporting our results, and discuss possible experimental realizations in solid-state and cold-atom systems.

Serbyn, M.; Knap, M.; Gopalakrishnan, S.; Papi?, Z.; Yao, N. Y.; Laumann, C. R.; Abanin, D. A.; Lukin, M. D.; Demler, E. A.

2014-10-01

167

Few-body Physics in a Many-body World

The study of quantum mechanical few-body systems is a century old pursuit relevant to countless subfields of physics. While the two-body problem is generally considered to be well-understood theoretically and numerically, venturing to three or more bodies brings about complications but also a host of interesting phenomena. In recent years, the cooling and trapping of atoms and molecules has shown great promise to provide a highly controllable environment to study few-body physics. However, as is true for many systems where few-body effects play an important role the few-body states are not isolated from their many-body environment. An interesting question then becomes if or (more precisely) when we should consider few-body states as effectively isolated and when we have to take the coupling to the environment into account. Using some simple, yet non-trivial, examples I will try to suggest possible approaches to this line of research.

N. T. Zinner

2014-01-03

168

Many body population trapping in ultracold dipolar gases

NASA Astrophysics Data System (ADS)

A system of interacting dipoles is of paramount importance for understanding many-body physics. The interaction between dipoles is anisotropic and long-range. While the former allows one to observe rich effects due to different geometries of the system, long-range (1/{{r}^{3}}) interactions lead to strong correlations between dipoles and frustration. In effect, interacting dipoles in a lattice form a paradigmatic system with strong correlations and exotic properties with possible applications in quantum information technologies, and as quantum simulators of condensed matter physics, material science, etc. Notably, such a system is extremely difficult to model due to a proliferation of interaction induced multi-band excitations for sufficiently strong dipole-dipole interactions. In this article we develop a consistent theoretical model of interacting polar molecules in a lattice by applying the concepts and ideas of ionization theory which allows us to include highly excited Bloch bands. Additionally, by involving concepts from quantum optics (population trapping), we show that one can induce frustration and engineer exotic states, such as Majumdar-Ghosh state, or vector-chiral states in such a system.

Dutta, Omjyoti; Lewenstein, Maciej; Zakrzewski, Jakub

2014-05-01

169

Collision rates for many body encounters

Rarefied gas dynamics has traditionally been founded on the dilute gas assumption, which presupposes that the densities are so low that only binary collisions and single-body gas surface interactions occur. However, expressions for many-body collision rates and for many-body gas surface interaction (GSI) rates seem to suggest that at lower heights the dilute gas assumption is not valid. In particular,

A. A. Agbormbai

2001-01-01

170

H theorem for many body collisions

Although rarefied gas dynamics has traditionally stood on the dilute gas assumption, which supposes that the densities are so low that only binary collisions and single-body gas surface interactions occur, expressions for many-body collision rates and for many-body gas surface interaction (GSI) rates seem to suggest that at lower heights the dilute gas assumption is not valid. In particular, in

A. A. Agbormbai

2001-01-01

171

Local Conservation Laws and the Structure of the Many-Body Localized States

NASA Astrophysics Data System (ADS)

We construct a complete set of local integrals of motion that characterize the many-body localized (MBL) phase. Our approach relies on the assumption that local perturbations act locally on the eigenstates in the MBL phase, which is supported by numerical simulations of the random-field XXZ spin chain. We describe the structure of the eigenstates in the MBL phase and discuss the implications of local conservation laws for its nonequilibrium quantum dynamics. We argue that the many-body localization can be used to protect coherence in the system by suppressing relaxation between eigenstates with different local integrals of motion.

Serbyn, Maksym; Papi?, Z.; Abanin, Dmitry A.

2013-09-01

172

Novel solvable variants of the goldfish many-body model

NASA Astrophysics Data System (ADS)

A recent technique to identify solvable many-body problems in two-dimensional space yields, via a new twist, new many-body problems of "goldfish" type. Some of these models are isochronous, namely their generic solutions are completely periodic with a fixed period (independent of the initial data). The investigation of the behavior of some of these isochronous systems in the vicinity of their equilibrium configurations yields some amusing diophantine relations.

Bruschi, M.; Calogero, F.

2006-02-01

173

High precision framework for chaos many-body engine

NASA Astrophysics Data System (ADS)

In this paper we present a C# 4.0 high precision framework for simulation of relativistic many-body systems. In order to benefit from the, previously developed, chaos analysis instruments, all new modules were integrated with Chaos Many-Body Engine (Grossu et al. 2010, 2013). As a direct application, we used 46 digits precision for analyzing the "Butterfly Effect" of the gravitational force in a specific relativistic nuclear collision toy-model.

Grossu, I. V.; Besliu, C.; Felea, D.; Jipa, Al.

2014-04-01

174

Observation of coherent quench dynamics in a metallic many-body state of fermions

The investigation of nonequilibrium dynamics in interacting quantum many-body systems has emerged as a key approach to characterize the nature of quantum states, to study excitation spectra, and to shed light on thermalization processes. So far, research on nonequilibrium dynamics has focused on many-body quantum states of bosonic particles, leading to the observation of coherent quench dynamics and the exploration of relaxation and thermalization in isolated quantum systems. Here we report on the observation of coherent quench dynamics in a many-body quantum state of fermionic particles. In the experiment, we prepare a metallic state of ultracold spin-polarized fermionic atoms in a shallow three-dimensional (3D) optical lattice. The delocalized fermions are in contact with a Bose-Einstein condensate (BEC) that is simultaneously loaded into the lattice. With a rapid increase of lattice depth, we take the system out of equilibrium and induce quench dynamics that is driven by the interactions between fermions and bosons. We observe the time evolution of the fermionic momentum distribution, which shows long-lived coherent oscillations for up to ten periods, both for attractive and repulsive Fermi-Bose interactions. A theoretical model reveals that the dynamics arises as a consequence of the delocalized nature of the initial fermionic state and the on-site number fluctuations of the BEC. Our work demonstrates that coherent quench dynamics constitutes a powerful technique to gain insight into the nature of fermionic quantum many-body states and to accurately determine Hamiltonian parameters used in their microscopic description.

Sebastian Will; Deepak Iyer; Marcos Rigol

2014-06-10

175

Reciprocity theory of many-body interactions

The reciprocity approach is applied to the problem of many body interactions in which an arbitrary number of molecules simultaneously collide with one another at the same impact point in physical space. First, the relevant features in the theory of binary collisions are reviewed, and then the problem of three bodies is considered. It is shown that this reduces to

Adolf A. Agbormbai

1990-01-01

176

Neutrino diffraction induced by many body interaction

The neutrino produced in the pion decay reveals a new diffraction phenomenon due to many-body interactions in an intermediate time region when wave functions of the parent and daughters overlap. Because of diffraction, the probability to detect the neutrino involves a large finite-size correction that depends on the neutrino mass, $m_{\

Kenzo Ishikawa; Yutaka Tobita

2011-06-24

177

PREFACE: 17th International Conference on Recent Progress in Many-Body Theories (MBT17)

NASA Astrophysics Data System (ADS)

These are the proceedings of the XVII International Conference on Recent Progress in Many-Body Theories, which was held from 8-13 September 2013 in Rostock, Germany. The conference continued the triennial series initiated in Trieste in 1978 and was devoted to new developments in the field of many-body theories. The conference series encourages the exchange of ideas between physicists working in such diverse areas as nuclear physics, quantum chemistry, lattice Hamiltonians or quantum uids. Many-body theories are an integral part in different fields of theoretical physics such as condensed matter, nuclear matter and field theory. Phase transitions and macroscopic quantum effects such as magnetism, Bose-Einstein condensation, super uidity or superconductivity have been investigated within ultra-cold gases, finite systems or various nanomaterials. The conference series on Recent Progress in Many-Body Theories is devoted to foster the interaction and to cross-fertilize between different fields and to discuss future lines of research. The topics of the 17th meeting were Cluster Physics Cold Gases High Energy Density Matter and Intense Lasers Magnetism New Developments in Many-Body Techniques Nuclear Many-Body and Relativistic Theories Quantum Fluids and Solids Quantum Phase Transitions Topological Insulators and Low Dimensional Systems. 109 participants from 20 countries participated. 44 talks and 61 posters werde presented. As a particular highlight of the conference, The Eugene Feenberg Memorial Medal for outstanding results in the field of many-body theory and The Hermann Kümmel Early Achievement Award in Many-Body Physics for young scientists in that field were awarded. The Feenberg Medal went jointly to Patrick Lee (MIT, USA) for his fundamental contributions to condensed-matter theory, especially in regard to the quantum Hall effect, to universal conductance uctuations, and to the Kondo effect in quantum dots, and Douglas Scalapino (UC Santa Barbara, USA) for his imaginative use and development of the Monte-Carlo approach and for his ground-breaking contributions to superconductivity. The Kümmel Award went to Max Metlitski (UC Santa Barbara) for remarkable advances in the theory of quantum criticality in metals. The nominations for the Kümmel Award were of such high standard that the Committee announced Honourable Mentions to Martin Eckstein (MPDS/U Hamburg, Germany) for his leading contributions in the development of non-equilibrium dynamical mean field theory, Emanuel Gull (U Michigan, USA) for the development of the Continuous-Time Auxiliary-Field Quantum Monte Carlo Method and for its use in understanding the interplay of the pseudogap and superconductivity in the Hubbard model and Kai Sun (U Michigan, USA) for seminal contributions to the theory of topological effects in strongly correlated electron systems. The Conference continues the series of conferences held before in Trieste, Italy (1979); Oaxtapec, Mexico (1981); Odenthal-Altenberg, Germany (1983); San Francisco, USA (1985); Oulu, Finland (1987); Arad, Israel (1989); Minneapolis, USA (1991); Schloé Segau, Austria (1994); Sydney, Australia (1997); Seattle, USA (1999); Manchester, UK (2001); Santa Fe, USA (2004); Buenos Aires, Argentina (2005); Barcelona, Spain (2007); Columbus, USA (2009) and Bariloche, Argentina (2011). It has been a great pleasure to prepare for the conference. We thank the IAC and in particular Susana Hernandez and David Neilson as well as the International Programme Committee for their great support and advice. Many more people have been involved locally in organizing this international meeting and thanks goes to them, in particular to the members of the LOC Sonja Lorenzen, Dieter Bauer, Niels-Uwe Bastian, Marina Hertzfeldt, Volker Mosert and Gerd Röpke. The next meeting will take place in Buffalo, USA in 2015 and we look forward to yet another exciting exchange on Recent Progress in Many-Body Theories. Heidi Reinholz and Jordi Boronat Guest editors Conference photograph Details of the committees are available in the PDF.

Reinholz, Heidi; Boronat, Jordi

2014-08-01

178

Many-body physics of slow light

We study the properties of slow light propagating under the electromagnetically induced transparency condition in a medium consisting of a mesoscopic number of atoms (~100). This system can be mapped onto the generalized Tavis-Cummings model. The exact diagonalization of the latter's Hamiltonian yields the spectrum of dark polaritons. These fully quantum results are found to be in a good agreement with the mean-field approach.

I. E. Mazets

2014-04-14

179

NASA Astrophysics Data System (ADS)

An explicit set of ordinary differential equations that approximately describe the dynamics of many rigid bodies (without any hypothesis on their geometry) inside an ideal fluid is presented. Two applications of these equations are made. At first, it is shown how to use these equations to compute the added-mass tensor of a single body made up of simpler units (like spheres, cylinders, and ellipsoids). Then the hydrodynamic force and torque that a small-amplitude fast oscillating body induces on another body that can freely move in its vicinity is computed. The noticeable result is that if the free body is sufficiently far from the oscillating one then the averaged interaction force is attractive if and only if the density of the free body is larger than the density of the fluid. Finally, computations for a pendulum system are presented. It seems that the latter system is suitable for experimentation.

Ragazzo, Clodoaldo Grotta

2002-05-01

180

The self-healing diffusion Monte Carlo algorithm (SHDMC) [Reboredo, Hood and Kent, Phys. Rev. B {\\bf 79}, 195117 (2009); Reboredo, {\\it ibid.} {\\bf 80}, 125110 (2009)] is extended to study the ground and excited states of magnetic and periodic systems. The method converges to exact eigenstates as the statistical data collected increases if the wave function is sufficiently flexible. A recursive optimization algorithm is derived from the time evolution of the mixed probability density, which is given by an ensemble of electronic configurations (walkers) with complex weight. This complex weight allows the amplitude of the fixed-node wave function to move away from the trial wave function phase. This novel approach is both a generalization of SHDMC and the fixed-phase approximation [Ortiz, Ceperley and Martin, Phys Rev. Lett. {\\bf 71}, 2777 (1993)]. When used recursively it simultaneously improves the node and the phase. The algorithm is demonstrated to converge to nearly exact solutions of model systems with pe...

Reboredo, Fernando Agustín

2010-01-01

181

The self-healing diffusion Monte Carlo algorithm (SHDMC) [Reboredo, Hood and Kent, Phys. Rev. B {\\bf 79}, 195117 (2009), Reboredo, {\\it ibid.} {\\bf 80}, 125110 (2009)] is extended to study the ground and excited states of magnetic and periodic systems. A recursive optimization algorithm is derived from the time evolution of the mixed probability density. The mixed probability density is given by an ensemble of electronic configurations (walkers) with complex weight. This complex weigh allows the amplitude of the fix-node wave function to move away from the trial wave function phase. This novel approach is both a generalization of SHDMC and the fixed-phase approximation [Ortiz, Ceperley and Martin Phys Rev. Lett. {\\bf 71}, 2777 (1993)]. When used recursively it improves simultaneously the node and phase. The algorithm is demonstrated to converge to the nearly exact solutions of model systems with periodic boundary conditions or applied magnetic fields. The method is also applied to obtain low energy excitations with magnetic field or periodic boundary conditions. The potential applications of this new method to study periodic, magnetic, and complex Hamiltonians are discussed.

Reboredo, Fernando A [ORNL

2012-01-01

182

Alternative formulation of many-body perturbation theory for electron–proton correlation

We present a formulation of nuclear-electronic many-body perturbation theory for treating electron–proton correlation. Our analysis indicates that removal of the proton–proton Coulomb-exchange operator from the reference Hamiltonian can lead to a significantly lower second-order energy and potentially faster convergence of the perturbation series for many-electron systems with a single quantum nucleus and many classical nuclei. This alternative reference Hamiltonian gives

Chet Swalina; Michael V. Pak; Sharon Hammes-Schiffer

2005-01-01

183

Goldfishing: A new solvable many-body problem

NASA Astrophysics Data System (ADS)

A recent technique allows one to identify and investigate solvable dynamical systems naturally interpretable as classical many-body problems, being characterized by equations of motion of Newtonian type (generally in two-dimensional space). In this paper we tersely review results previously obtained in this manner and present novel findings of this kind: mainly solvable variants of the goldfish many-body model, including models that feature isochronous classes of completely periodic solutions. Different formulations of these models are presented. The behavior of one of these isochronous dynamical systems in the neighborhood of its equilibrium configuration is investigated, and in this manner some remarkable Diophantine findings are obtained.

Bruschi, M.; Calogero, F.

2006-10-01

184

Normal and superconducting many-body systems

NASA Astrophysics Data System (ADS)

This thesis consists of three Chapters. In the first Chapter, based on a planar unconventional Fermi liquid model, we present several results on the optimally doped and overdoped cuprate superconductors. For the normal state, we have analytically derived a linear in temperature and energy scattering rate for the carriers. This scattering rate yields necessarily a linear in temperature resistivity and a linear in 1/energy optical conductivity. The linearity of the scattering rate requires that the interacting Fermi liquid has strong peaks in its density of states (van-Hove singularities in 2 dimensions) near the chemical potential mu. Our results are backed by self-consistent Baym-Kadanoff (BK) numerical calculations. We show that the low energy dependence of the Millis-Monien-Pines susceptibility chisb{MMP} can have a fermionic origin. We obtain particularly high transition temperatures Tsb{c} from our BK-Eliashberg scheme by introducing an ansatz for the susceptibility of the carriers. We postulate that the latter is enhanced in an additive manner due to the weak antiferromagnetic order of the CuOsb2 planes. Thus we have obtained a dsb{xsp2-ysp2} gap with Tsb{c} > 120sp°K for nearest neighbor hopping t = 250meV. In the second Chapter we propose a novel mechanism for giant corrections to the transport quantities, including positive giant magnetoresistance, due to the presence of paramagnons in a weakly disordered metal. We obtain very good agreement between this theory and four (4) different positive giant magnetoresistance experiments, including very recent ones, while making specific material-dependent predictions. We emphasize that our theory broadens the 'conventional wisdom' viewpoint that weak disorder would only generate small corrections to transport quantities. In the third Chapter we examine the effects of interface roughness and/or planar impurity doping in a superlattice, under the assumption that a weak disorder description is adequate. This study can offer quantitative insight to transport properties of multilayers and devices, which contain inadvertently structural disorder at the interfaces.

Kastrinakis, George

1998-08-01

185

Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoherence

NASA Astrophysics Data System (ADS)

Central spin decoherence caused by nuclear spin baths is often a critical issue in various quantum computing schemes, and it has also been used for sensing single-nuclear spins. Recent theoretical studies suggest that central spin decoherence can act as a probe of many-body physics in spin baths; however, identification and detection of many-body correlations of nuclear spins in nanoscale systems are highly challenging. Here, taking a phosphorus donor electron spin in a 29Si nuclear spin bath as our model system, we discover both theoretically and experimentally that many-body correlations in nanoscale nuclear spin baths produce identifiable signatures in decoherence of the central spin under multiple-pulse dynamical decoupling control. We demonstrate that under control by an odd or even number of pulses, the central spin decoherence is principally caused by second- or fourth-order nuclear spin correlations, respectively. This study marks an important step toward studying many-body physics using spin qubits.

Ma, Wen-Long; Wolfowicz, Gary; Zhao, Nan; Li, Shu-Shen; Morton, John J. L.; Liu, Ren-Bao

2014-09-01

186

Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoherence

Central spin decoherence caused by nuclear spin baths is often a critical issue in various quantum computing schemes, and it has also been used for sensing single-nuclear spins. Recent theoretical studies suggest that central spin decoherence can act as a probe of many-body physics in spin baths; however, identification and detection of many-body correlations of nuclear spins in nanoscale systems are highly challenging. Here, taking a phosphorus donor electron spin in a 29Si nuclear spin bath as our model system, we discover both theoretically and experimentally that many-body correlations in nanoscale nuclear spin baths produce identifiable signatures in decoherence of the central spin under multiple-pulse dynamical decoupling control. We demonstrate that under control by an odd or even number of pulses, the central spin decoherence is principally caused by second- or fourth-order nuclear spin correlations, respectively. This study marks an important step toward studying many-body physics using spin qubits. PMID:25205440

Ma, Wen-Long; Wolfowicz, Gary; Zhao, Nan; Li, Shu-Shen; Morton, John J.L.; Liu, Ren-Bao

2014-01-01

187

Recent Progress in Many-Body Theories: Proceedings of the 12th International Conference

NASA Astrophysics Data System (ADS)

Preface -- International advisory committee -- Feenberg medal session. Surface and superconductivity / L. P. Gor'kov. Spartak T. Belyaev - recipient of the Feenberg Medal / V. Zelevinsky. Many-body physics and spontaneous symmetry breaking / S. T. Belyaev -- Keynote speaker. The future lies ahead / P. W. Anderson -- Strongly correlated systems and phase transitions. Exact results for many-body problems using few-body methods / J. Cardy. Quantum matters: physics beyond Landau's paradigms / T. Senthil. Microscopic calculations of quantum phase transitions in frustrated magnetic lattices / R. F. Bishop & S. E. Krüger. Recent applications of the DMRG method / K. Hallberg. Functional renormalization group in the 2D Hubbard model / C. Honerkamp. Quantum phase transitions and event horizons: condensed matter analogies / G. Chapline. Spin-charge separation and topological phase transitions in Aharnov-Bohm rings of interacting electrons / B. Normand ... [et al.] -- Quantum fluids and solids. Two-particle-two-hole excitations in [symbol]He / E. Krotscheck, H. M. Böhm & K. Schörkhuber. Monolayer charged quantum films: a quantum simulation study / K. Wierschem & E. Manousakis. Can inconmensuration stabilize a superfluid phase of para-hydrogen? / M. Boninsegni. Analysis of the interatomic potential of the helium systems / S. Ujevic & S. A. Vitiello -- Nuclear physics and QCD. Quantum phase transitions in mesoscopic systems / F. Iachello. Nuclear-structure theory in the search for new fundamental physics / J. Engel. Matter at extreme density and its role in neutron stars and supernova / S. Reddy. New approaches to strong coupling lattice QCD / S. Chandrasekharan. Nuclear interactions from the renormalization group / A. Schwenk. Random interactions and ground state spin of finite Fermi systems / V. Zelevinsky & A. Volya -- Cold atoms and quantum information. Superfluid regimes in degenerate atomic fermi gases / G. V. Shlyapnikov. Bosons in optical lattices / S. L. Rolston. Generalized entanglement and quantum phase transitions / R. Somma ... [et al.]. Ground state of many-body lattice systems via a central limit theorem / C. Presilla & M. Ostilli. Effects of a single quantum spin on Josephson oscillations / M. Hru\\vska ... [et al.] -- Complex systems. Spin textures and random fields in dirty quantum hall ferromagnets / J. T. Chalker. Dissipative quantum disordered models / L. F. Cugliandolo. Possibly exact solution for the multicritical point of finite-dimensional spin glasses / H. Nishimori, K. Takeda & T. Sasamoto. From statistical physics methods to algorithms / D. Battaglia, M. Kola? & R. Zecchina.

Carlson, Joseph A.; Ortiz, Gerardo

2006-07-01

188

Many-body dynamics of dipolar molecules in an optical lattice

Understanding the many-body dynamics of isolated quantum systems is one of the central challenges in modern physics. To this end, the direct experimental realization of strongly correlated quantum systems allows one to gain insights into the emergence of complex phenomena. Such insights enable the development of theoretical tools that broaden our understanding. Here, we theoretically model and experimentally probe with Ramsey spectroscopy the quantum dynamics of disordered, dipolar-interacting, ultracold molecules in a partially filled optical lattice. We report the capability to control the dipolar interaction strength, and we demonstrate that the many-body dynamics extends well beyond a nearest-neighbor or mean-field picture, and cannot be quantitatively described using previously available theoretical tools. We develop a novel cluster expansion technique and demonstrate that our theoretical method accurately captures the measured dependence of the spin dynamics on molecule number and on the dipolar interaction strength. In the spirit of quantum simulation, this agreement simultaneously benchmarks the new theoretical method and verifies our microscopic understanding of the experiment. Our findings pave the way for numerous applications in quantum information science, metrology, and condensed matter physics.

Kaden R. A. Hazzard; Bryce Gadway; Michael Foss-Feig; Bo Yan; Steven A. Moses; Jacob P. Covey; Norman Y. Yao; Mikhail D. Lukin; Jun Ye; Deborah S. Jin; Ana Maria Rey

2014-02-11

189

Many-body luminescence from a ring-shaped dot: Luttinger liquid theory

NASA Astrophysics Data System (ADS)

Luminescence spectrum of a single photoexcited quantum dot represents a system of very narrow spectral lines corresponding to optical transitions within confined exciton multiplexes.^1 We study theoretically the shape of the luminescence spectrum for quantum dots of a ring geometry, which have been recently fabricated.^2,3 For high excitation intensities, photoexcited electrons and holes form Fermi seas in conduction and valence bands, thus allowing to adopt the Lutinger liquid description. The recombination of an electron-hole pair is accompanied by the emission of the Fermi sea excitations (shake-up effect). We have calculated analytically the oscillator strengths of the many-body luminescence lines as a function of the interaction strength. We find that close to the emission threshold, the many-body lines constitute weak satellites of single-particle transitions. However, away from the emission threshold, the shape of the spectrum is comletely dominated by many-body transitions. ^1See, e.g., E. Dekel et. al, Phys. Rev B 61, 11009 (2000); ibid. 62, 11038 (2000). ^2A. Lorke et. al, Phys. Rev. Lett. 84, 2223 (2000). ^3R. J. Warburton et al, Nature 405, 926 (2000).

Shahbazyan, T. V.; Perakis, I. E.; Raikh, M. E.

2001-03-01

190

Many-body forces and the cluster decomposition

Direct-interaction dynamics is considered in the relativistic Hamiltonian constraint formalism. It is proven that the Todorov-Komar equations for an N-particle system (N>2) of mutually interacting particles have no solutions that permit interaction if only two-body forces are admitted. The inclusion of many-body forces leads to a system of equations that determines allowed classes of such forces recursively. Starting with given

F. Rohrlich

1981-01-01

191

Thermalization of an Open Quantum System Via Full Diagonalization

NASA Astrophysics Data System (ADS)

Thermalization, the irreversible relaxation of a system to thermodynamic equilibrium, ultimately arises from the reversible dynamics of many-body quantum systems. Weakly coupling a small system to a large many-body quantum system (heat bath) results in the equilibration of the small system to the Boltzmann distribution. We solve numerically, using full diagonalization, a model in which a small system is coupled to a large quantum system, and retrieve the thermodynamic behavior from the underlying quantum mechanics. We discuss the mechanism of thermalization, and the applications of our simulation for exploring the behavior of damped quantum systems.

Jacobs, K.; Silvestri, Luciano

192

High precision framework for Chaos Many-Body Engine

In this paper we present a C# 4.0 high precision framework for simulation of relativistic many-body systems. In order to benefit from, previously developed, chaos analysis instruments, all new modules were designed to be integrated with Chaos Many-Body Engine [1,3]. As a direct application, we used 46 digits precision for analyzing the Butterfly Effect of the gravitational force in a specific relativistic nuclear collision toy-model. Trying to investigate the average Lyapunov Exponent dependency on the incident momentum, an interesting case of intermittency was noticed. Based on the same framework, other high-precision simulations are currently in progress (e.g. study on the possibility of considering, hard to detect, extremely low frequency photons as one of the dark matter components).

I. V. Grossu; C. Besliu; D. Felea; Al. Jipa

2013-03-04

193

Superadiabatic Forces in Brownian Many-Body Dynamics

NASA Astrophysics Data System (ADS)

Theoretical approaches to nonequilibrium many-body dynamics generally rest upon an adiabatic assumption, whereby the true dynamics is represented as a sequence of equilibrium states. Going beyond this simple approximation is a notoriously difficult problem. For the case of classical Brownian many-body dynamics, we present a simulation method that allows us to isolate and precisely evaluate superadiabatic correlations and the resulting forces. Application of the method to a system of one-dimensional hard particles reveals the importance for the dynamics, as well as the complexity, of these nontrivial out-of-equilibrium contributions. Our findings help clarify the status of dynamical density functional theory and provide a rational basis for the development of improved theories.

Fortini, Andrea; de las Heras, Daniel; Brader, Joseph M.; Schmidt, Matthias

2014-10-01

194

Influence of many-body interactions during the ionization of gases by short intense optical pulses.

The excitation of atomic gases by short high-intensity optical pulses leads to significant electron ionization. In dilute systems, the generated distribution of ionized electrons is highly anisotropic, reflecting the quantum mechanical properties of the atomic states involved in the many photon transitions. For higher atomic densities, the Coulomb interaction in the electron-ion system leads to the development of an isotropic electron plasma. To study the ionization process in the presence of the many-body interaction, a fully microscopic model is developed that combines a generalized version of the optical Bloch equations describing the optical excitation with a microscopic description of the many-body interactions. The numerical evaluation shows that the Coulomb interaction significantly modifies the distribution anisotropy already during the excitation process. Whereas a reduced anisotropy is still present after the pulse for low ionization degrees and pressures, it is completely absent for elevated gas densities. An ionization degree is predicted that is significantly enhanced by the many-body interactions. PMID:24730952

Schuh, K; Hader, J; Moloney, J V; Koch, S W

2014-03-01

195

Many-body theory of indirect nuclear interactions

NASA Astrophysics Data System (ADS)

We derive an expression for the indirect nuclear coupling tensor (A??jj') including spin-orbit and many-body effects. We use a finite-temperature Green's-function method where the thermodynamic potential is expressed in terms of the exact one-particle propagator and the proper self-energy, and derive a general expression for A??jj' in the Bloch representation. While the effects of spin-orbit interaction appear in our expression through the modification of the one-particle eigenvalues and eigenstates and through a change in the orbital hyperfine interaction via the modification of the electronic momentum operator, the many-body effects are more subtle. We find that the many-body corrections to A??jj' in the quasiparticle approximation are cancelled in part by the inclusion of exchange and correlation effects. We also show, by making drastic assumptions while solving the matrix integral equations for the nuclear spin-dependent part of the self-energy, that the exchange enhancement effects in a band model on A??jj' are different for different terms. The remarkability of the theory is that for the first time a systematic effort has been made to study the effects of electron-electron interaction on the various contributions to A??jj'. We also discuss the importance of relativistic and electron-electron interaction effects in the calculation of the coupling constant in real systems. The theory is general and can be applied to metals, semiconductors, and insulators.

Tripathi, Gouri S.

1985-04-01

196

Machine learning for many-body physics: The case of the Anderson impurity model

NASA Astrophysics Data System (ADS)

Machine learning methods are applied to finding the Green's function of the Anderson impurity model, a basic model system of quantum many-body condensed-matter physics. Different methods of parametrizing the Green's function are investigated; a representation in terms of Legendre polynomials is found to be superior due to its limited number of coefficients and its applicability to state of the art methods of solution. The dependence of the errors on the size of the training set is determined. The results indicate that a machine learning approach to dynamical mean-field theory may be feasible.

Arsenault, Louis-François; Lopez-Bezanilla, Alejandro; von Lilienfeld, O. Anatole; Millis, Andrew J.

2014-10-01

197

NASA Astrophysics Data System (ADS)

The energy and entanglement spectrum of fractionally filled interacting topological insulators exhibit a peculiar manifold of low-energy states separated by a gap from a high-energy set of spurious states. In the current paper, we show that in the case of fractionally filled Chern insulators, the topological information of the many-body state developing in the system resides in this low-energy manifold. We identify an emergent many-body translational symmetry which allows us to separate the states in quasidegenerate center-of-mass momentum sectors. Within one center-of-mass sector, the states can be further classified as eigenstates of an emergent (in the thermodynamic limit) set of many-body relative translation operators. We analytically establish a mapping between the two-dimensional Brillouin zone for the fractional quantum Hall effect on the torus and the one for the fractional Chern insulator. We show that the counting of quasidegenerate levels below the gap for the fractional Chern insulator should arise from a folding of the states in the fractional quantum Hall system at an identical filling factor. We show how to count and separate the excitations of the Laughlin, Moore-Read, and Read-Rezayi series in the fractional quantum Hall effect into two-dimensional Brillouin zone momentum sectors and then how to map these into the momentum sectors of the fractional Chern insulator. We numerically check our results by showing the emergent symmetry at work for Laughlin, Moore-Read, and Read-Rezayi states on the checkerboard model of a Chern insulator, thereby also showing, as a proof of principle, that non-Abelian fractional Chern insulators exist.

Bernevig, B. Andrei; Regnault, N.

2012-02-01

198

In the spectrum of many-body quantum systems, the low-energy eigenstates were the traditional focus of research. The interest in the statistical properties of the full eigenspectrum has grown more recently, in particular in the context of non-equilibrium questions. Wave functions of interacting lattice quantum systems can be characterized either by local observables, or by global properties such as the participation ratio (PR) in a many-body basis or the entanglement between various partitions. We present a study of the PR and of the entanglement entropy (EE) between two roughly equal spatial partitions of the system, in all the eigenfunctions of local Hamiltonians. Motivated by the similarity of the PR and EE - both are generically larger in the bulk and smaller near the edges of the spectrum - we quantitatively analyze the correlation between them. We elucidate the effect of (proximity to) integrability, showing how low-entanglement and low-PR states appear also in the middle of the spectrum as one approaches integrable points. We also determine the precise scaling behavior of the eigenstate-to-eigenstate fluctuations of the PR and EE with respect to system size, and characterize the statistical distribution of these quantities near the middle of the spectrum.

Wouter Beugeling; Alexei Andreanov; Masudul Haque

2014-10-28

199

Quantum simulations with 8?8?Sr+? ions on planar lattice traps

Quantum simulations are the use of well controlled many-body quantum systems to simulate and solve other many-body quantum systems that are not understood. This thesis describes theoretical proposals and experimental ...

Lin, Ziliang (Ziliang Carter)

2008-01-01

200

No-go theorem for one-way quantum computing on naturally occurring two-level systems

The ground states of some many-body quantum systems can serve as resource states for the one-way quantum computing model, achieving the full power of quantum computation. Such resource states are found, for example, in ...

Chen, Jianxin

201

Constructing local integrals of motion in the many-body localized phase

Many-body localization provides a generic mechanism of ergodicity breaking in quantum systems. In contrast to conventional ergodic systems, many-body localized (MBL) systems are characterized by extensively many local integrals of motion (LIOM), which underlie the absence of transport and thermalization in these systems. Here we report a physically motivated construction of local integrals of motion in the MBL phase. We show that any local operator (e.g., a local particle number or a spin flip operator), evolved with the system's Hamiltonian and averaged over time, becomes a LIOM in the MBL phase. Such operators have a clear physical meaning, describing the response of the MBL system to a local perturbation. In particular, when a local operator represents a density of some globally conserved quantity, the corresponding LIOM describes how this conserved quantity propagates through the MBL phase. Being uniquely defined and experimentally measurable, these LIOMs provide a natural tool for characterizing the properties of the MBL phase, both in experiments and numerical simulations. We demonstrate the latter by numerically constructing an extensive set of LIOMs in the MBL phase of a disordered spin chain model. We show that the resulting LIOMs are quasi-local, and use their decay to extract the localization length and establish the location of the transition between the MBL and ergodic phases.

Anushya Chandran; Isaac H. Kim; Guifre Vidal; Dmitry A. Abanin

2014-07-31

202

The self-healing diffusion Monte Carlo method for complex functions [F. A. Reboredo J. Chem. Phys. {\\bf 136}, 204101 (2012)] and some ideas of the correlation function Monte Carlo approach [D. M. Ceperley and B. Bernu, J. Chem. Phys. {\\bf 89}, 6316 (1988)] are blended to obtain a method for the calculation of thermodynamic properties of many-body systems at low temperatures. In order to allow the evolution in imaginary time to describe the density matrix, we remove the fixed-node restriction using complex antisymmetric trial wave functions. A statistical method is derived for the calculation of finite temperature properties of many-body systems near the ground state. In the process we also obtain a parallel algorithm that optimizes the many-body basis of a small subspace of the many-body Hilbert space. This small subspace is optimized to have maximum overlap with the one expanded by the lower energy eigenstates of a many-body Hamiltonian. We show in a model system that the Helmholtz free energy is minimized within this subspace as the iteration number increases. We show that the subspace expanded by the small basis systematically converges towards the subspace expanded by the lowest energy eigenstates. Possible applications of this method to calculate the thermodynamic properties of many-body systems near the ground state are discussed. The resulting basis can be also used to accelerate the calculation of the ground or excited states with Quantum Monte Carlo.

Kim, Jeongnim [ORNL] [ORNL; Reboredo, Fernando A [ORNL] [ORNL

2014-01-01

203

Many-body functions of nonprimitive electrolytes in one dimension

NASA Astrophysics Data System (ADS)

The statistical mechanics of a mixture of hard-core ions and dipoles in one dimension, namely, the one-dimensional version of the so-called nonprimitive model of an electrolyte, is considered by stressing the effect of the charge-dipole interactions and the hard-core repulsions on the thermodynamics and, especially, on the many-body functions of the systems. The adaptation of Baxter's generating function technique to this model lets us express the thermodynamic and structural functions in terms of a non-Hermitian generalized Hill-type Hamiltonian. The eigenvalues and eigenfunctions of this differential operator yield, in closed form, the n-body correlation functions in the bulk and near the container's walls. We also comment on the screening of the electric fields by the system ions and study the Donnan equilibrium when one of the ionic species in the mixture cannot diffuse through a semipermeable membrane.

Vericat, Fernando; Blum, Lesser

1990-12-01

204

High precision module for Chaos Many-Body Engine

In this paper we present a C# high precision relativistic many-body module integrated with Chaos Many-Body Engine. As a direct application, we used it for estimating the butterfly effect involved by the gravitational force in a specific nuclear relativistic collision toy-model.

Grossu, I V; Felea, D; Jipa, Al

2014-01-01

205

NASA Astrophysics Data System (ADS)

We study theoretically the collective dynamics of rotational excitations of polar molecules loaded into an optical lattice in two dimensions. We explore the collective many-body phases that form following a microwave pulse. We show that, owing to the long-range interactions between molecules and energy conservation in this isolated system, the rotational excitations can form a Bose-Einstein condensate with long-range order, even for the natural (undressed) dipole interactions. This manifests itself as a divergent T2 coherence time of the rotational transition even in the presence of inhomogeneous broadening. The dynamical evolution of a dense gas of rotational excitations shows regimes of nonergodicity, characteristic of many-body localization and localization protected quantum order.

Kwasigroch, M. P.; Cooper, N. R.

2014-08-01

206

Matter wave optical techniques for probing many-body targets

This thesis reports on our investigation of the uses of matter waves to probe many-body targets. We begin by discussing decoherence in an atom interferometer, in which a free gas acts as a refractive medium for a matter ...

Sanders, Scott Nicholas

2010-01-01

207

Investigation of many-body forces in krypton and xenon

The simplicity of the state dependence at relatively high temperatures ofthe many-body potential contribution to the pressure and energy has been pointed out previously (J. Ram and P. A. Egelstaff, J. Phys. Chem. Liq. 14, 29 (1984); A. Teitsima and P. A. Egelstaff, Phys. Rev. A 21, 367 (1980)). In this paper, we investigate how far these many-body potential terms may be represented by simple models in the case of krypton on the 423-, 273-, 190-, and 150-K isotherms, and xenon on the 170-, 210-, and 270-K isotherms. At the higher temperatures the best agreement is found for the mean-field type of theory, and some consequences are pointed out. On the lower isotherms a state point is found where the many-body energy vanishes, and large departures from mean-field behavior are observed. This is attributed to the influence of short-ranged many-body forces.

Salacuse, J.J.; Egelstaff, P.A.

1988-10-15

208

Communication: Random phase approximation renormalized many-body perturbation theory

We derive a renormalized many-body perturbation theory (MBPT) starting from the random phase approximation (RPA). This RPA-renormalized perturbation theory extends the scope of single-reference MBPT methods to small-gap systems without significantly increasing the computational cost. The leading correction to RPA, termed the approximate exchange kernel (AXK), substantially improves upon RPA atomization energies and ionization potentials without affecting other properties such as barrier heights where RPA is already accurate. Thus, AXK is more balanced than second-order screened exchange [A. Grüneis et al., J. Chem. Phys. 131, 154115 (2009)], which tends to overcorrect RPA for systems with stronger static correlation. Similarly, AXK avoids the divergence of second-order Møller-Plesset (MP2) theory for small gap systems and delivers a much more consistent performance than MP2 across the periodic table at comparable cost. RPA+AXK thus is an accurate, non-empirical, and robust tool to assess and improve semi-local density functional theory for a wide range of systems previously inaccessible to first-principles electronic structure calculations.

Bates, Jefferson E.; Furche, Filipp, E-mail: filipp.furche@uci.edu [Department of Chemistry, University of California, Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025 (United States)] [Department of Chemistry, University of California, Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025 (United States)

2013-11-07

209

Communication: Random phase approximation renormalized many-body perturbation theory

NASA Astrophysics Data System (ADS)

We derive a renormalized many-body perturbation theory (MBPT) starting from the random phase approximation (RPA). This RPA-renormalized perturbation theory extends the scope of single-reference MBPT methods to small-gap systems without significantly increasing the computational cost. The leading correction to RPA, termed the approximate exchange kernel (AXK), substantially improves upon RPA atomization energies and ionization potentials without affecting other properties such as barrier heights where RPA is already accurate. Thus, AXK is more balanced than second-order screened exchange [A. Grüneis et al., J. Chem. Phys. 131, 154115 (2009)], which tends to overcorrect RPA for systems with stronger static correlation. Similarly, AXK avoids the divergence of second-order Møller-Plesset (MP2) theory for small gap systems and delivers a much more consistent performance than MP2 across the periodic table at comparable cost. RPA+AXK thus is an accurate, non-empirical, and robust tool to assess and improve semi-local density functional theory for a wide range of systems previously inaccessible to first-principles electronic structure calculations.

Bates, Jefferson E.; Furche, Filipp

2013-11-01

210

Communication: Random phase approximation renormalized many-body perturbation theory.

We derive a renormalized many-body perturbation theory (MBPT) starting from the random phase approximation (RPA). This RPA-renormalized perturbation theory extends the scope of single-reference MBPT methods to small-gap systems without significantly increasing the computational cost. The leading correction to RPA, termed the approximate exchange kernel (AXK), substantially improves upon RPA atomization energies and ionization potentials without affecting other properties such as barrier heights where RPA is already accurate. Thus, AXK is more balanced than second-order screened exchange [A. Grüneis et al., J. Chem. Phys. 131, 154115 (2009)], which tends to overcorrect RPA for systems with stronger static correlation. Similarly, AXK avoids the divergence of second-order Møller-Plesset (MP2) theory for small gap systems and delivers a much more consistent performance than MP2 across the periodic table at comparable cost. RPA+AXK thus is an accurate, non-empirical, and robust tool to assess and improve semi-local density functional theory for a wide range of systems previously inaccessible to first-principles electronic structure calculations. PMID:24206280

Bates, Jefferson E; Furche, Filipp

2013-11-01

211

Stochastic many-body perturbation theory for anharmonic molecular vibrations

NASA Astrophysics Data System (ADS)

A new quantum Monte Carlo (QMC) method for anharmonic vibrational zero-point energies and transition frequencies is developed, which combines the diagrammatic vibrational many-body perturbation theory based on the Dyson equation with Monte Carlo integration. The infinite sums of the diagrammatic and thus size-consistent first- and second-order anharmonic corrections to the energy and self-energy are expressed as sums of a few m- or 2m-dimensional integrals of wave functions and a potential energy surface (PES) (m is the vibrational degrees of freedom). Each of these integrals is computed as the integrand (including the value of the PES) divided by the value of a judiciously chosen weight function evaluated on demand at geometries distributed randomly but according to the weight function via the Metropolis algorithm. In this way, the method completely avoids cumbersome evaluation and storage of high-order force constants necessary in the original formulation of the vibrational perturbation theory; it furthermore allows even higher-order force constants essentially up to an infinite order to be taken into account in a scalable, memory-efficient algorithm. The diagrammatic contributions to the frequency-dependent self-energies that are stochastically evaluated at discrete frequencies can be reliably interpolated, allowing the self-consistent solutions to the Dyson equation to be obtained. This method, therefore, can compute directly and stochastically the transition frequencies of fundamentals and overtones as well as their relative intensities as pole strengths, without fixed-node errors that plague some QMC. It is shown that, for an identical PES, the new method reproduces the correct deterministic values of the energies and frequencies within a few cm-1 and pole strengths within a few thousandths. With the values of a PES evaluated on the fly at random geometries, the new method captures a noticeably greater proportion of anharmonic effects.

Hermes, Matthew R.; Hirata, So

2014-08-01

212

Transport properties of quantum-classical systems.

Correlation function expressions for calculating transport coefficients for quantum-classical systems are derived. The results are obtained by starting with quantum transport coefficient expressions and replacing the quantum time evolution with quantum-classical Liouville evolution, while retaining the full quantum equilibrium structure through the spectral density function. The method provides a variety of routes for simulating transport coefficients of mixed quantum-classical systems, composed of a quantum subsystem and a classical bath, by selecting different but equivalent time evolution schemes of any operator or the spectral density. The structure of the spectral density is examined for a single harmonic oscillator where exact analytical results can be obtained. The utility of the formulation is illustrated by considering the rate constant of an activated quantum transfer process that can be described by a many-body bath reaction coordinate. PMID:15974726

Kim, Hyojoon; Kapral, Raymond

2005-06-01

213

Many-body Rabi oscillations of Rydberg excitation in small mesoscopic samples

We investigate the collective aspects of Rydberg excitation in ultracold mesoscopic systems. Strong interactions between Rydberg atoms influence the excitation process and impose correlations between excited atoms. The manifestations of the collective behavior of Rydberg excitation are the many-body Rabi oscillations, spatial correlations between atoms as well as the fluctuations of the number of excited atoms. We study these phenomena in detail by numerically solving the many-body Schr\\"edinger equation.

J. Stanojevic; R. Côté

2008-01-15

214

A three-dimensional attractive Bose-Einstein condensate is expected to collapse when the number of the particles N in the ground state or the interaction strength {lambda}{sub 0} exceeds a critical value. We study systems of different particle numbers and interaction strength and find that even if the overall ground state is collapsed there is a plethora of fragmented excited states that are still in the metastable region. Utilizing the configuration interaction expansion we determine the spectrum of the ground (''yrast'') and excited many-body states with definite total angular-momentum quantum numbers 0{<=}L{<=}N and -L{<=}M{sub L{<=}}L, and we find and examine states that survive the collapse. This opens up the possibility of realizing a metastable system with overcritical numbers of bosons in a ground state with angular momentum L{ne}0. The multiorbital mean-field theory predictions about the existence of fragmented metastable states with overcritical numbers of bosons are verified and elucidated at the many-body level. The descriptions of the total angular momentum within the mean-field and the many-body approaches are compared.

Tsatsos, Marios C.; Streltsov, Alexej I.; Alon, Ofir E.; Cederbaum, Lorenz S. [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany)

2010-09-15

215

Short History of Nuclear Many-Body Problem

This is a very short presentation regarding developments in the theory of nuclear many-body problems, as seen and experienced by the author during the past 60 years with particular emphasis on the contributions of Gerry Brown and his research-group. Much of his work was based on Brueckner's formulation of the nuclear many-body problem. It is reviewed briefly together with the Moszkowski-Scott separation method that was an important part of his early work. The core-polarisation and his work related to effective interactions in general are also addressed.

H. S. Köhler

2014-05-02

216

221B Lecture Notes Many-Body Problems IV

221B Lecture Notes Many-Body Problems IV Nuclear Physics 1 Nuclei Nuclei sit at the center of any. Due to some reason, however, the nuclear physics had not been taught so much in the standard physics curriculum. I try to briefly review nuclear physics in a few lectures. Obviously I can't go into much details

Murayama, Hitoshi

217

221B Lecture Notes Many-Body Problems II

221B Lecture Notes Many-Body Problems II Nuclear Physics 1 Nuclei Nuclei sit at the center of any. Due to some reason, however, the nuclear physics had not been taught so much in the standard physics curriculum. I try to briefly review nuclear physics in about a week. Obviously I can't go into much details

Murayama, Hitoshi

218

Rapid mixing renders quantum dissipative systems stable

The physics of many materials is modeled by quantum many-body systems with local interactions. If the model of the system is sensitive to noise from the environment, or small perturbations to the original interactions, it will not model properly the robustness of the real physical system it aims to describe, or be useful when engineering novel systems for quantum information processing. We show that local observables and correlation functions of local Liouvillians are stable to local perturbations if the dynamics is rapidly mixing and has a unique fixed point. No other condition is required.

Angelo Lucia; Toby S. Cubitt; Spyridon Michalakis; David Pérez-García

2014-09-27

219

Many-body polarization effects and the membrane dipole potential.

Molecular dynamics simulations of a lipid monolayer at a water-air interface are used to investigate the dipole potential that arises at the water-lipid interface. One simulation explicitly accounts for many-body polarization effects by using a model based on classical Drude oscillators. The dipole potential of the Drude model monolayer is 0.35V in excellent agreement with experimental estimates that range between 0.3 and 0.4V, whereas, a simulation using a nonpolarizable model significantly overestimates the potential with a calculated value of 0.8V. Induced polarization effects in the nonpolar region of the monolayer are found to buffer the residual positive lipid potential that results from competing polarization effects at the polar water/monolayer interface. These results, indicate the utility of the inclusion of many-body polarization effects in empirical force field models of lipids.

Harder, E.; MacKerell, A. D.; Roux, B. (Biosciences Division); (Univ. of Chicago); (Univ. of Maryland)

2009-01-01

220

Convergence properties of multireference many-body perturbation theory

The applicability of multireference many-body perturbation theory is considered by numerically investigating the practical convergence properties of a common variant. Perturbation energies through 20th order are reported for BeH2 at geometries near the Be-->H2 symmetric-insertion transition state and for BH in its equilibrium region. The recursive perturbation-theory equations are solved using a computationally intensive, but conceptually simple, configuration-based algorithm. In

S. Zarrabian; W. D. Laidig; Rodney J. Bartlett

1990-01-01

221

NASA Astrophysics Data System (ADS)

A recently proposed Markov approach provides Lindblad-type scattering superoperators, which ensure the physical (positive-definite) character of the many-body density matrix. We apply the mean-field approximation to such a many-body equation, in the presence of one- and two-body scattering mechanisms, and we derive a closed equation of motion for the electronic single-particle density matrix, which turns out to be nonlinear as well as non-Lindblad. We prove that, in spite of its nonlinear and non-Lindblad structure, the mean-field approximation does preserve the positive-definite character of the single-particle density matrix, an essential prerequisite of any reliable kinetic treatment of semiconductor quantum devices. This result is in striking contrast with conventional (non-Lindblad) Markov approaches, where the single-particle mean-field equations can lead to positivity violations and thus to unphysical results. Furthermore, the proposed single-particle formulation is extended to the case of quantum systems with spatial open boundaries, providing a formal derivation of a recently proposed density-matrix treatment based on a Lindblad-like system-reservoir scattering superoperator.

Rosati, Roberto; Iotti, Rita Claudia; Dolcini, Fabrizio; Rossi, Fausto

2014-09-01

222

Many-Body Effects on Bandgap Shrinkage, Effective Masses, and Alpha Factor

NASA Technical Reports Server (NTRS)

Many-body Coulomb effects influence the operation of quantum-well (QW) laser diode (LD) strongly. In the present work, we study a two-band electron-hole plasma (EHP) within the Hatree-Fock approximation and the single plasmon pole approximation for static screening. Full inclusion of momentum dependence in the many-body effects is considered. An empirical expression for carrier density dependence of the bandgap renormalization (BGR) in an 8 nm GaAs/Al(0.3)G(4.7)As single QW will be given, which demonstrates a non-universal scaling behavior for quasi-two-dimension structures, due to size-dependent efficiency of screening. In addition, effective mass renormalization (EMR) due to momentum-dependent self-energy many-body correction, for both electrons and holes is studied and serves as another manifestation of the many-body effects. Finally, the effects on carrier density dependence of the alpha factor is evaluated to assess the sensitivity of the full inclusion of momentum dependence.

Li, Jian-Zhong; Ning, C. Z.; Woo, Alex C. (Technical Monitor)

2000-01-01

223

Lefschetz thimble Monte Carlo for many-body theories: A Hubbard model study

NASA Astrophysics Data System (ADS)

Recently, a method based on stochastic integration on the surfaces of steepest descent of the action was introduced to tackle the sign problem in quantum-field theories. We show how this method can be used in many-body theories to perform fully nonperturbative calculations of quantum corrections about mean-field solutions. We discuss an explicit algorithm for implementing our method, and present results for the repulsive Hubbard model away from half-filling at intermediate temperatures. Our results are consistent with those from other state-of-the-art calculations.

Mukherjee, Abhishek; Cristoforetti, Marco

2014-07-01

224

A statistical method is derived for the calculation of thermodynamic properties of many-body systems at low temperatures. This method is based on the self-healing diffusion Monte Carlo method for complex functions [F. A. Reboredo, J. Chem. Phys. 136, 204101 (2012)] and some ideas of the correlation function Monte Carlo approach [D. M. Ceperley and B. Bernu, J. Chem. Phys. 89, 6316 (1988)]. In order to allow the evolution in imaginary time to describe the density matrix, we remove the fixed-node restriction using complex antisymmetric guiding wave functions. In the process we obtain a parallel algorithm that optimizes a small subspace of the many-body Hilbert space to provide maximum overlap with the subspace spanned by the lowest-energy eigenstates of a many-body Hamiltonian. We show in a model system that the partition function is progressively maximized within this subspace. We show that the subspace spanned by the small basis systematically converges towards the subspace spanned by the lowest energy eigenstates. Possible applications of this method for calculating the thermodynamic properties of many-body systems near the ground state are discussed. The resulting basis can also be used to accelerate the calculation of the ground or excited states with quantum Monte Carlo. PMID:24559334

Reboredo, Fernando A; Kim, Jeongnim

2014-02-21

225

Three-body decay of many-body resonances

We use the hyperspherical coordinates to describe decay of many-body resonances. Direct and sequential decay are described by different paths in the distances between the particles. We generalize the WKB expression for the {alpha}-decay width to decay of three charged particles. Decay mechanisms and resonance structures are computed in coordinate space. The energy distributions of the particles after decay are discussed. Moderate s-wave scattering lengths prefer decay via corresponding virtual state possibly leaving unique fingerprints of this reminiscence of the Efimov effect in the decay of excited states. Numerical illustrations are resonances in 6He, 12C, 17Ne.

Jensen, A.S.; Fedorov, D.V.; Fynbo, H.O.U. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Garrido, E. [Instituto de Estructura de la Materia, CSIC, Serrano 123, E-28006 Madrid (Spain)

2005-10-14

226

Collective Many-Body Interaction in Rydberg Dressed Atoms

We present a method to control the shape and character of the interaction potential between cold atomic gases by weakly dressing the atomic ground state with a Rydberg level. For increasing particle densities, a crossover takes place from a two-particle interaction into a collective many-body interaction, where the dipole-dipole or van der Waals blockade phenomenon between the Rydberg levels plays a dominant role. We study the influence of these collective interaction potentials on a Bose-Einstein condensate and present the optimal parameters for its experimental detection.

Honer, Jens; Weimer, Hendrik; Buechler, Hans Peter [Institute for Theoretical Physics III, University of Stuttgart, Stuttgart (Germany); Pfau, Tilman [5. Physikalische Institut, University of Stuttgart, Stuttgart (Germany)

2010-10-15

227

and a many-body energy decomposition scheme for the explicit polarization plus symmetry-adapted perturbation, and on this basis we introduce an energy decomposition scheme that extends tradi- tional SAPT energy decomposition to systems containing more than two monomers. For (H2O)6, the many-body contribution to the interaction

Herbert, John

228

Effective field theory for neutron stars with genuine many-body forces

NASA Astrophysics Data System (ADS)

The aim of our contribution is to shed some light on open questions facing the high density nuclear many-body problem. We focus our attention on the conceptual issue of naturalness and its role for the baryon-meson coupling for nuclear matter at high densities. As a guideline for the strengths of the various couplings the concept of naturalness has been adopted. In order to encourage possible new directions of research, we discuss relevant aspects of a relativistic effective theory for nuclear matter with {``natural''} parametric couplings and genuine many-body forces. Among other topics, we discuss in this work the connection of this theory with other known effective Quantum Hadrodynamics (QHD) models found in literature and how we can potentially use our approach to describe new physics for neutron stars. We also show some preliminary results for the equation of state, population profiles and mass-radius relation for neutron stars assuming local charge neutrality and beta equilibrium.

Vasconcellos , C. A. Z.; Gomes, R. O.; Dexheimer, V.; Negreiros, R. P.; Horvath, J.; Hadjimichef, D.

2014-09-01

229

Effective Field Theory for Neutron Stars with Genuine Many-body Forces

The aim of our contribution is to shed some light on open questions facing the high density nuclear many-body problem. We focus our attention on the conceptual issue of naturalness and its role for the baryon-meson coupling for nuclear matter at high densities. As a guideline for the strengths of the various couplings the concept of naturalness has been adopted. In order to encourage possible new directions of research, we discuss relevant aspects of a relativistic effective theory for nuclear matter with natural parametric couplings and genuine many-body forces. Among other topics, we discuss in this work the connection of this theory with other known effective Quantum Hadrodynamics (QHD) models found in literature and how we can potentially use our approach to describe new physics for neutron stars. We also show some preliminary results for the equation of state, population profiles and mass-radius relation for neutron stars assuming local charge neutrality and beta equilibrium.

Vasconcellos, C A Z; Dexheimer, V; Negreiros, R P; Horvath, J; Hadjimichef, D

2014-01-01

230

Effective Field Theory for Neutron Stars with Genuine Many-body Forces

The aim of our contribution is to shed some light on open questions facing the high density nuclear many-body problem. We focus our attention on the conceptual issue of naturalness and its role for the baryon-meson coupling for nuclear matter at high densities. As a guideline for the strengths of the various couplings the concept of naturalness has been adopted. In order to encourage possible new directions of research, we discuss relevant aspects of a relativistic effective theory for nuclear matter with natural parametric couplings and genuine many-body forces. Among other topics, we discuss in this work the connection of this theory with other known effective Quantum Hadrodynamics (QHD) models found in literature and how we can potentially use our approach to describe new physics for neutron stars. We also show some preliminary results for the equation of state, population profiles and mass-radius relation for neutron stars assuming local charge neutrality and beta equilibrium.

C. A. Z. Vasconcellos; R. O. Gomes; V. Dexheimer; R. P. Negreiros; J. Horvath; D. Hadjimichef

2014-02-23

231

Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoherence

Many-body correlations can yield key insights into the nature of interacting systems; however, detecting them is often very challenging in many-particle physics, especially in nanoscale systems. Here, taking a phosphorus donor electron spin in a natural-abundance 29Si nuclear spin bath as our model system, we discover both theoretically and experimentally that many-body correlations in nanoscale nuclear spin baths produce identifiable signatures in the decoherence of the central spin under multiple-pulse dynamical decoupling control. We find that when the number of decoupling -pulses is odd, central spin decoherence is primarily driven by second-order nuclear spin correlations (pairwise flip-flop processes). In contrast, when the number of -pulses is even, fourth-order nuclear spin correlations (diagonal interaction renormalized pairwise flip-flop processes) are principally responsible for the central spin decoherence. Many-body correlations of different orders can thus be selectively detected by central spin decoherence under different dynamical decoupling controls, providing a useful approach to probing many-body processes in nanoscale nuclear spin baths.

Wen-Long Ma; Gary Wolfowicz; Nan Zhao; Shu-Shen Li; John J. L. Morton; Ren-Bao Liu

2014-04-10

232

Effective Operators from Exact Many-Body Renormalization

We construct effective two-body Hamiltonians and E2 operators for the p-shell by performing 16{h_bar}{Omega} ab initio no-core shell model (NCSM) calculations for A = 5 and A = 6 nuclei and explicitly projecting the many-body Hamiltonians and E2 operator onto the 0{h_bar}{Omega} space. We then separate the effective E2 operator into one-body and two-body contributions employing the two-body valence cluster approximation. We analyze the convergence of proton and neutron valence one-body contributions with increasing model space size and explore the role of valence two-body contributions. We show that the constructed effective E2 operator can be parametrized in terms of one-body effective charges giving a good estimate of the NCSM result for heavier p-shell nuclei.

Lisetskiy, A F; Kruse, M G; Barrett, B R; Navratil, P; Stetcu, I; Vary, J P

2009-06-11

233

Many-body tight-binding model for aluminum nanoparticles

A new, parametrized many-body tight-binding model is proposed for calculating the potential energy surface for aluminum nanoparticles. The parameters have been fitted to reproduce the energies for a variety of aluminum clusters (Al{sub 2}, Al{sub 3}, Al{sub 4}, Al{sub 7}, Al{sub 13}) calculated recently by the PBE0/MG3 method as well as the experimental face-centered-cubic cohesive energy, lattice constant, and a small set of Al cluster ionization potentials. Several types of parametrization are presented and compared. The mean unsigned error per atom for the best model is less than 0.03 eV.

Staszewska, Grazyna; Staszewski, Przemyslaw; Schultz, Nathan E.; Truhlar, Donald G. [Institute of Physics, Nicolaus Copernicus University, ul. Grudziadzka 5, 87-100 Torun (Poland); Department of Theoretical Foundations of Biomedical Sciences and Medical Informatics, Collegium Medicum, Nicolaus Copernicus University, ul. Jagiellonska 13, 85-067 Bydgoszcz (Poland); Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 44455-0431 (United States)

2005-01-15

234

Another New Solvable Many-Body Model of Goldfish Type

NASA Astrophysics Data System (ADS)

A new solvable many-body problem is identified. It is characterized by nonlinear Newtonian equations of motion (''acceleration equal force'') featuring one-body and two-body velocity-dependent forces ''of goldfish type'' which determine the motion of an arbitrary number N of unit-mass point-particles in a plane. The N (generally complex) values z_{n}( t) at time t of the N coordinates of these moving particles are given by the N eigenvalues of a time-dependent N× N matrix U( t) explicitly known in terms of the 2N initial data z_{n}( 0) and dot{z}_{n}(0) . This model comes in two different variants, one featuring 3 arbitrary coupling constants, the other only 2; for special values of these parameters all solutions are completely periodic with the same period independent of the initial data (''isochrony''); for other special values of these parameters this property holds up to corrections vanishing exponentially as t? ? (''asymptotic isochrony''). Other isochronous variants of these models are also reported. Alternative formulations, obtained by changing the dependent variables from the N zeros of a monic polynomial of degree N to its N coefficients, are also exhibited. Some mathematical findings implied by some of these results - such as Diophantine properties of the zeros of certain polynomials - are outlined, but their analysis is postponed to a separate paper.

Calogero, Francesco

2012-07-01

235

Band structure of polyethylene from many-body perturbation theory

NASA Astrophysics Data System (ADS)

The electronic structure of polyethylene is an important benchmark and the infinite chain limit for the electronic properties of many molecules, monolayers, and oligomers. Therefore, the band structure of the ideal, one-dimensional polyethylene chain has been extensively researched, from both the experimental and the theoretical viewpoints. Despite this extensive effort, to the best of our knowledge agreement between theoretical calculations and the electronic structure obtained from photoelectron spectroscopy could only be obtained using artificial shifting and ``stretching'' of the computed data. Here, we present a quantitative quasi-particle band-structure for polyethylene using many-body perturbation theory. The approach is employed within the G0W0 approximation, based on a starting point calculated within the generalized gradient approximation to density functional theory. We compare our calculated band-structure to angle resolved photoemission spectroscopy measurements for various long saturated carbohydrates, demonstrate a much improved agreement with experiment, and discuss remaining discrepancies and their possible origins within both theory and experiment.

Biller, Ariel; Sharifzadeh, Sahar; Segev, Lior; Ismail-Beigi, Sohrab; Neaton, Jeffrey B.; Kronik, Leeor

2013-03-01

236

NASA Astrophysics Data System (ADS)

High quality epitaxial graphene films can be applied as templates for tailoring graphene–substrate interfaces that allow for precise control of the charge carrier behavior in graphene through doping and many-body effects. By combining scanning tunneling microscopy, angle-resolved photoemission spectroscopy and density functional theory we demonstrate that oxygen intercalated epitaxial graphene on Ir(111) has high structural quality, is quasi free-standing, and shows signatures of many-body interactions. Using this system as a template, we show that pn-interfaces can be patterned by adsorption and intercalation of rubidium, and that the n-doped graphene regions exhibit a reduced Coulomb screening via enhanced electron–plasmon coupling. These findings are central for understanding and tailoring the properties of graphene-metal contacts e.g. for realizing quantum tunneling devices.

Ulstrup, Søren; Andersen, Mie; Bianchi, Marco; Barreto, Lucas; Hammer, Bjørk; Hornekær, Liv; Hofmann, Philip

2014-09-01

237

Novel solvable extensions of the goldfish many-body model

NASA Astrophysics Data System (ADS)

A novel solvable extension of the goldfish N-body problem is presented. Its Newtonian equations of motion read ??n=2a?\\dot n?n+2?m =1,m?nN(?\\dot n-a?n2)(?\\dot m-a?m2)/(?n-?m), n =1,…,N, where a is an arbitrary (nonvanishing) constant and the rest of the notation is self-evident. The isochronous version of this model is characterized by the Newtonian equations of motion ??n-3i?\\zdot n-2?2zn=2a(\\zdot n-i?zn)zn+2?m =1,m?nN(\\zdot n-i?zn-azn2)(\\zdot m-i?zm-azm2)/(zn-zm), n =1,…,N, where ? is an arbitrary positive constant and the points zn(t) move now necessarily in the complex z-plane. The generic solution of this second model is completely periodic with a period Tk=kT which is an integer multiple k (not larger than N!, indeed generally much smaller) of the basic period T =2?/? and which is independent of the initial data (for sufficiently small, but otherwise arbitrary, changes of such data). These many-body models have an intriguing variety of equilibrium configurations (genuine: with no two particles sitting at the same place), but only for small values of N (N =2,3,4 for the first model, N =2,3,4,5 for the second). Other versions of these models are also discussed. The study of the behavior of the second, isochronous model around its equilibrium configurations yields some amusing diophantine results.

Calogero, F.; Iona, S.

2005-10-01

238

Holographic Duality with a View Toward Many-Body Physics

These are notes based on a series of lectures given at the KITP workshop Quantum Criticality and the AdS/CFT Correspondence in July, 2009. The goal of the lectures was to introduce condensed matter physicists to the AdS/CFT ...

McGreevy, John

239

GEOMETRY AND ANALYSIS IN MANY-BODY SCATTERING 1. Introduction

;guration space and phase space. This geometry is closely related to classical mechanics, playing the role, namely the propagation of singularities connecting classical and quantum mechanics. Much as for the wave in Hiroshi Isozaki's lecture notes [30]. Indeed, in some sense, the current notes continue where [30] left o

Vasy, AndrÃ¡s

240

A many-body potential approach to modelling the thermomechanical properties of actinide oxides.

A many-body potential model for the description of actinide oxide systems, which is robust at high temperatures, is reported for the first time. The embedded atom method is used to describe many-body interactions ensuring good reproduction of a range of thermophysical properties (lattice parameter, bulk modulus, enthalpy and specific heat) between 300 and 3000 K for AmO2, CeO2, CmO2, NpO2, ThO2, PuO2 and UO2. Additionally, the model predicts a melting point for UO2 between 3000 and 3100 K, in close agreement with experiment. Oxygen-oxygen interactions are fixed across the actinide oxide series because it facilitates the modelling of oxide solid solutions. The new potential is also used to predict the energies of Schottky and Frenkel pair disorder processes. PMID:24553129

Cooper, M W D; Rushton, M J D; Grimes, R W

2014-03-12

241

Recent development of complex scaling method for many-body resonances and continua in light nuclei

NASA Astrophysics Data System (ADS)

The complex scaling method (CSM) is a useful similarity transformation of the Schrödinger equation, in which bound-state spectra are not changed but continuum spectra are separated into resonant and non-resonant continuum ones. Because the asymptotic wave functions of the separated resonant states are regularized by the CSM, many-body resonances can be obtained by solving an eigenvalue problem with the L2 basis functions. Applying this method to a system consisting of a core and valence nucleons, we investigate many-body resonant states in weakly bound nuclei very far from the stability lines. Non-resonant continuum states are also obtained with the discretized eigenvalues on the rotated branch cuts. Using these complex eigenvalues and eigenstates in CSM, we construct the extended completeness relations and Green's functions to calculate strength functions and breakup cross sections. Various kinds of theoretical calculations and comparisons with experimental data are presented.

Myo, Takayuki; Kikuchi, Yuma; Masui, Hiroshi; Kat?, Kiyoshi

2014-11-01

242

Entanglement in fermion systems and quantum metrology

Entanglement in fermion many-body systems is studied using a generalized definition of separability based on partitions of the set of observables, rather than on particle tensor products. In this way, the characterizing properties of non-separable fermion states can be explicitly analyzed, allowing a precise description of the geometric structure of the corresponding state space. These results have direct applications in fermion quantum metrology: sub-shot noise accuracy in parameter estimation can be obtained without the need of a preliminary state entangling operation.

F. Benatti; R. Floreanini; U. Marzolino

2014-03-05

243

Entanglement in fermion systems and quantum metrology

Entanglement in fermion many-body systems is studied using a generalized definition of separability based on partitions of the set of observables, rather than on particle tensor products. In this way, the characterizing properties of non-separable fermion states can be explicitly analyzed, allowing a precise description of the geometric structure of the corresponding state space. These results have direct applications in fermion quantum metrology: sub-shot noise accuracy in parameter estimation can be obtained without the need of a preliminary state entangling operation.

Benatti, F; Marzolino, U

2014-01-01

244

Periodic thermodynamics of isolated quantum systems.

The nature of the behavior of an isolated many-body quantum system periodically driven in time has been an open question since the beginning of quantum mechanics. After an initial transient period, such a system is known to synchronize with the driving; in contrast to the nondriven case, no fundamental principle has been proposed for constructing the resulting nonequilibrium state. Here, we analytically show that, for a class of integrable systems, the relevant ensemble is constructed by maximizing an appropriately defined entropy subject to constraints, which we explicitly identify. This result constitutes a generalization of the concepts of equilibrium statistical mechanics to a class of far-from-equilibrium systems, up to now mainly accessible using ad hoc methods. PMID:24785013

Lazarides, Achilleas; Das, Arnab; Moessner, Roderich

2014-04-18

245

Many-body correlations of electrostatically trapped dipolar excitons

NASA Astrophysics Data System (ADS)

We study the photoluminescence (PL) of a two-dimensional liquid of oriented dipolar excitons in InxGa1-xAs coupled double quantum wells confined to a microtrap. Generating excitons outside the trap and transferring them at lattice temperatures down to T=240 mK into the trap we create cold quasiequilibrium bosonic ensembles of some 1000 excitons with thermal de Broglie wavelengths exceeding the excitonic separation. With decreasing temperature and increasing density n?5×1010(1)/(cm2) we find an increasingly asymmetric PL line shape with a sharpening blue edge and a broad red tail which we interpret to reflect correlated behavior mediated by dipolar interactions. From the PL intensity I(E) below the PL maximum at E0 we extract at T<5 K a distinct power law I(E)˜(E0-E)-|?| with -|?|?-0.8 in the range E0-E of 1.5-4 meV, comparable to the dipolar interaction energy.

Schinner, G. J.; Repp, J.; Schubert, E.; Rai, A. K.; Reuter, D.; Wieck, A. D.; Govorov, A. O.; Holleitner, A. W.; Kotthaus, J. P.

2013-05-01

246

Quantum Monte Carlo Methods for Strongly Correlated Electron Systems

We review some of the recent development in quantum Monte Carlo (QMC) methods for models of strongly correlated electron systems.\\u000a QMC is a promising general theoretical tool to study many-body systems, and has been widely applied in areas spanning condensed-matter,\\u000a high-energy, and nuclear physics. Recent progress has included two new methods, the ground-state and finite-temperature constrained\\u000a path Monte Carlo methods.

Shiwei Zhang

247

Nonequilibrium Quantum Breakdown in a Strongly Correlated Electron System

During the past decades, there has been an increasing fascination and surprises with diverse quantum many-body effects. With the magical touch of interaction a simple electron system may assume insulating, metallic, magnetic or superconducting\\u000a states according as the control parameters are changed. Strongly correlated electron systems, as exemplified by the high-Tc\\u000a superconductors and their host materials realized in transition-metal oxides,

Takashi Oka; Hideo Aoki

2008-01-01

248

Irreducible Scalar Many-Body Casimir Energies: Theorems and Numerical Studies

We define irreducible N-body spectral functions and Casimir energies and consider a massless scalar quantum field interacting locally by positive potentials with classical objects. Irreducible N-body spectral functions in this case are shown to be conditional probabilities of random walks. The corresponding irreducible contributions to scalar many-body Casimir energies are finite and positive/negative for an odd/even number of objects. The force between any two finite objects separable by a plane is always attractive in this case. Analytical and numerical world-line results for the irreducible four-body Casimir energy of a scalar with Dirichlet boundary conditions on a tic-tac-toe pattern of lines are presented. Numerical results for the irreducible three-body Casimir energy of a massless scalar satisfying Dirichlet boundary conditions on three intersecting lines forming an isosceles triangle are also reported. In both cases the symmetric configuration (square and isosceles triangle) corresponds to the minima...

Schaden, Martin

2011-01-01

249

Strong local passivity in finite quantum systems.

Passive states of quantum systems are states from which no system energy can be extracted by any cyclic (unitary) process. Gibbs states of all temperatures are passive. Strong local (SL) passive states are defined to allow any general quantum operation, but the operation is required to be local, being applied only to a specific subsystem. Any mixture of eigenstates in a system-dependent neighborhood of a nondegenerate entangled ground state is found to be SL passive. In particular, Gibbs states are SL passive with respect to a subsystem only at or below a critical system-dependent temperature. SL passivity is associated in many-body systems with the presence of ground state entanglement in a way suggestive of collective quantum phenomena such as quantum phase transitions, superconductivity, and the quantum Hall effect. The presence of SL passivity is detailed for some simple spin systems where it is found that SL passivity is neither confined to systems of only a few particles nor limited to the near vicinity of the ground state. PMID:25122271

Frey, Michael; Funo, Ken; Hotta, Masahiro

2014-07-01

250

Solvable Many-Body Models of Goldfish Type with One-, Two- and Three-Body Forces

NASA Astrophysics Data System (ADS)

The class of solvable many-body problems ''of goldfish type'' is extended by including (the additional presence of) three-body forces. The solvable N-body problems thereby identified are characterized by Newtonian equations of motion featuring 19 arbitrary ''coupling constants''. Restrictions on these constants are identified which cause these systems - or appropriate variants of them - to be isochronous or asymptotically isochronous, i.e. all their solutions to be periodic with a fixed period (independent of the initial data) or to have this property up to contributions vanishing exponentially as t? ?.

Bihun, Oksana; Calogero, Francesco

2013-10-01

251

Photon-induced sideband transitions in a many-body Landau-Zener process

NASA Astrophysics Data System (ADS)

We investigate the many-body Landau-Zener (LZ) process in a two-site Bose-Hubbard model driven by a time-periodic field. We find that the driving field may induce sideband transitions in addition to the main LZ transitions. These photon-induced sideband transitions are a signature of the photon-assisted tunneling in our many-body LZ process. In the Rabi regime, where the system is dominated by the intermode coupling, the system can be looked as an ensemble of identical noninteracting single-particle LZ systems and the photon-induced sideband transitions are similar to the ones in single-particle LZ systems. In the Fock regime, where the system is dominated by the interparticle interaction, we develop an analytical theory for understanding the sideband transitions, which is confirmed by our numerical simulation. Furthermore, we discuss the quantization of the driving field. In the effective model of the quantized driving field, the sideband transitions can be understood as the LZ transitions between states of different "photon" numbers.

Zhong, Honghua; Xie, Qiongtao; Huang, Jiahao; Qin, Xizhou; Deng, Haiming; Xu, Jun; Lee, Chaohong

2014-08-01

252

Symmetric Tensor Decomposition Description of Fermionic Many-Body Wavefunctions

The configuration interaction (CI) is a versatile wavefunction theory for interacting fermions but it involves an extremely long CI series. Using a symmetric tensor decomposition (STD) method, we convert the CI series into a compact and numerically tractable form. The converted series encompasses the Hartree-Fock state in the first term and rapidly converges to the full-CI state, as numerically tested using small molecules. Provided that the length of the STD-CI series grows only moderately with the increasing complexity of the system, the new method will serve as one of the alternative variational methods to achieve full-CI with enhanced practicability.

Uemura, Wataru

2012-01-01

253

The relativistic many body problem with an oscillator interaction

NASA Technical Reports Server (NTRS)

We start with the total energy E for a system of three scalar relativistic particles that, because of Einstein's relation, will have square roots of functions of the momenta. By taking powers of this relation, we finally get a fourth degree polynomial in E(exp 2), where the square roots have disappeared, and which we can convert into a type of Schroedinger equation. To be in the center of mass frame we pass to Jocobi momenta and then replace them by creation and annihilation operators. We thus get an equation in terms of the generators of a U(2) group, which, in principle, we can solve in an elementary way. Finally, we rewrite our equation in a Poincare invariant form.

Moshinsky, Marcos

1995-01-01

254

The damping of the harmonic oscillator is studied in the framework of the\\u000aLindblad theory for open quantum systems. A generalization of the fundamental\\u000aconstraints on quantum mechanical diffusion coefficients which appear in the\\u000amaster equation for the damped quantum oscillator is presented; the\\u000aSchr\\\\\\

A. Isar; A. Sandulescu; H. Scutaru; E. Stefanescu; W. Scheid

2004-01-01

255

Quantum Mechanics + Open Systems

Quantum Mechanics + Open Systems = Thermodynamics ? Jochen Gemmer TÂ¨ubingen, 09.02.2006 #12., World Scientific) #12;Fundamental Law or Emergent Description? Quantum Mechanics i t = (- 2 2m + V or Emergent Description? Quantum Mechanics i t = (- 2 2m + V ) "Heisenberg Cut" Classical Mechanics: m d2

Steinhoff, Heinz-JÃ¼rgen

256

Open quantum system identification

Engineering quantum systems offers great opportunities both technologically and scientifically for communication, computation, and simulation. The construction and operation of large scale quantum information devices presents a grand challenge and a major issue is the effective control of coherent dynamics. This is often in the presence of decoherence which further complicates the task of determining the behaviour of the system. Here, we show how to determine open system Markovian dynamics of a quantum system with restricted initialisation and partial output state information.

Sophie G. Schirmer; Daniel K. L. Oi; Weiwei Zhou; Erling Gong; Ming Zhang

2012-05-28

257

Many-body Green's function study of coumarins for dye-sensitized solar cells

We study within the many-body Green's function $GW$ and Bethe-Salpeter formalisms the excitation energies of several coumarin dyes proposed as an efficient alternative to ruthenium complexes for dye-sensitized solar cells. Due to their internal donor-acceptor structure, these chromophores present low-lying excitations showing a strong intramolecular charge-transfer character. We show that combining $GW$ and Bethe-Salpeter calculations leads to charge-transfer excitation energies and oscillator strengths in excellent agreement with reference range-separated functional studies or coupled-cluster calculations. The present results confirm the ability of this family of approaches to describe accurately Frenkel and charge-transfer photo-excitations in both extended and finite size systems without any system-dependent adjustable parameter, paving the way to the study of dye-sensitized semiconducting surfaces.

Faber, C; Deutsch, T; Blase, X

2012-01-01

258

Loschmidt Echo and the Many-Body Orthogonality Catastrophe in a Qubit-Coupled Luttinger Liquid

NASA Astrophysics Data System (ADS)

We investigate the many-body generalization of the orthogonality catastrophe by studying the generalized Loschmidt echo of Luttinger liquids (LLs) after a global change of interaction. It decays exponentially with system size and exhibits universal behavior: the steady state exponent after quenching back and forth n times between 2 LLs (bang-bang protocol) is 2n times bigger than that of the adiabatic overlap and depends only on the initial and final LL parameters. These are corroborated numerically by matrix-product state based methods of the XXZ Heisenberg model. An experimental setup consisting of a hybrid system containing cold atoms and a flux qubit coupled to a Feshbach resonance is proposed to measure the Loschmidt echo using rf spectroscopy or Ramsey interferometry.

Dóra, Balázs; Pollmann, Frank; Fortágh, József; Zaránd, Gergely

2013-07-01

259

We describe a many-body quantum system which can be made to quantum compute by the adiabatic application of a large applied field to the system. Prior to the application of the field quantum information is localized on one boundary of the device, and after the application of the field this information has propagated to the other side of the device with a quantum circuit applied to the information. The applied circuit depends on the many-body Hamiltonian of the material, and the computation takes place in a degenerate ground space with symmetry-protected topological order. Such adiabatic quantum transistors are universal adiabatic quantum computing devices which have the added benefit of being modular. Here we describe this model, provide arguments for why it is an efficient model of quantum computing, and examine these many-body systems in the presence of a noisy environment.

Dave Bacon; Steven T. Flammia; Gregory M. Crosswhite

2012-07-11

260

We describe a many-body quantum system that can be made to quantum compute by the adiabatic application of a large applied field to the system. Prior to the application of the field, quantum information is localized on one boundary of the device, and after the application of the field, this information propagates to the other side of the device, with a quantum circuit applied to the information. The applied circuit depends on the many-body Hamiltonian of the material, and the computation takes place in a degenerate ground space with symmetry-protected topological order. Such “adiabatic quantum transistors” are universal adiabatic quantum computing devices that have the added benefit of being modular. Here, we describe this model, provide arguments for why it is an efficient model of quantum computing, and examine these many-body systems in the presence of a noisy environment.

Bacon, Dave; Flammia, Steven T.; Crosswhite, Gregory M.

2013-06-01

261

Irreducible Scalar Many-Body Casimir Energies: Theorems and Numerical Studies

NASA Astrophysics Data System (ADS)

We define irreducible N-body spectral functions and Casimir energies and consider a massless scalar quantum field interacting locally by positive potentials with classical objects. Irreducible N-body spectral functions in this case are shown to be conditional probabilities of random walks. The corresponding irreducible contributions to scalar many-body Casimir energies are finite and positive/negative for an odd/even number of objects. The force between any two finite objects separable by a plane is always attractive in this case. Analytical and numerical world-line results for the irreducible four-body Casimir energy of a scalar with Dirichlet boundary conditions on a tic-tac-toe pattern of lines are presented. Numerical results for the irreducible three-body Casimir energy of a massless scalar satisfying Dirichlet boundary conditions on three intersecting lines forming an isosceles triangle are also reported. In both cases the symmetric configuration (square and isosceles triangle) corresponds to the minimal irreducible contribution to the Casimir energy.

Schaden, Martin

2012-07-01

262

Many-body physics in the classical-field description of a degenerate Bose gas

The classical-field formalism has been widely applied in the calculation of normal correlation functions, and the characterization of condensation, in finite-temperature Bose gases. Here we discuss the extension of this method to the calculation of more general correlations, including the so-called anomalous correlations of the field, without recourse to symmetry-breaking assumptions. Our method is based on the introduction of U(1)-symmetric classical-field variables analogous to the modified quantum ladder operators of number-conserving approaches to the degenerate Bose gas, and allows us to rigorously quantify the anomalous and non-Gaussian character of the field fluctuations. We compare our results for anomalous correlation functions with the predictions of mean-field theories, and demonstrate that the nonlinear classical-field dynamics incorporate a full description of many-body processes which modify the effective mean-field potentials experienced by condensate and noncondensate atoms. We discuss the role of these processes in shaping the condensate mode, and thereby demonstrate the consistency of the Penrose-Onsager definition of the condensate orbital in the classical-field equilibrium. We consider the contribution of various noncondensate-field correlations to the overall suppression of density fluctuations and interactions in the field, and demonstrate the distinct roles of phase and density fluctuations in the transition of the field to the normal phase.

Wright, T. M.; Davis, M. J. [University of Queensland, School of Mathematics and Physics, ARC Centre of Excellence for Quantum-Atom Optics, Queensland 4072 (Australia); Proukakis, N. P. [School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom); University of Queensland, School of Mathematics and Physics, ARC Centre of Excellence for Quantum-Atom Optics, Queensland 4072 (Australia)

2011-08-15

263

Irreducible Scalar Many-Body Casimir Energies: Theorems and Numerical Studies

We define irreducible N-body spectral functions and Casimir energies and consider a massless scalar quantum field interacting locally by positive potentials with classical objects. Irreducible N-body spectral functions in this case are shown to be conditional probabilities of random walks. The corresponding irreducible contributions to scalar many-body Casimir energies are finite and positive/negative for an odd/even number of objects. The force between any two finite objects separable by a plane is always attractive in this case. Analytical and numerical world-line results for the irreducible four-body Casimir energy of a scalar with Dirichlet boundary conditions on a tic-tac-toe pattern of lines are presented. Numerical results for the irreducible three-body Casimir energy of a massless scalar satisfying Dirichlet boundary conditions on three intersecting lines forming an isosceles triangle are also reported. In both cases the symmetric configuration (square and isosceles triangle) corresponds to the minimal irreducible contribution to the Casimir energy.

Martin Schaden

2011-12-14

264

Electronic excitations of bulk LiCl from many-body perturbation theory

We present the quasiparticle band structure and the optical excitation spectrum of bulk LiCl, using many-body perturbation theory. Density-functional theory is used to calculate the ground-state geometry of the system. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into consideration, electron-hole pair states and optical excitations are obtained by solving the Bethe-Salpeter equation for the electron-hole two-particle Green function. The calculated band gap is 9.5 eV, which is in good agreement with the experimental result of 9.4 eV. And the calculated optical absorption spectrum, which contains an exciton peak at 8.8 eV and a resonant-exciton peak at 9.8 eV, is also in good agreement with experimental data.

Jiang, Yun-Feng; Wang, Neng-Ping, E-mail: wangnengping@nbu.edu.cn [Science Faculty, Ningbo University, Fenghua Road 818, 315211 Ningbo (China)] [Science Faculty, Ningbo University, Fenghua Road 818, 315211 Ningbo (China); Rohlfing, Michael [Institut für Festkörpertheorie, Universität Münster, 48149 Münster (Germany)] [Institut für Festkörpertheorie, Universität Münster, 48149 Münster (Germany)

2013-12-07

265

The fixed hypernode method for the solution of the many body Schroedinger equation

We propose a new scheme for an approximate solution of the Schroedinger equation for a many-body interacting system, based on the use of pairs of walkers. Trial wavefunctions for these pairs are combinations of standard symmetric and antisymmetric wavefunctions. The method consists in applying a fixed-node restriction in the enlarged space, and computing the energy of the antisymmetric state from the knowledge of the exact ground state energy for the symmetric state. We made two conjectures: first, that this fixed-hypernode energy is an upper bound to the true fermion energy; second that this bound would necessarily be lower than the usual fixed-node energy using the same antisymmetric trial function. The first conjecture is true, and is proved in this paper. The second is not, and numerical and analytical counterexamples are given. The question of whether the fixed-hypernode energy can be better than the usual bound remains open.

Pederiva, F; Kalos, M H; Reboredo, F; Bressanini, D; Guclu, D; Colletti, L; Umrigar, C J

2006-01-24

266

How Many-Body Effects Modify the van der Waals Interaction between Graphene Sheets

NASA Astrophysics Data System (ADS)

Undoped-graphene (Gr) sheets at low temperatures are known, via random-phase-approximation (RPA) calculations, to exhibit unusual van der Waals (vdW) forces. Here, we show that graphene is the first known system where effects beyond the RPA within each interacting subsystem make qualitative changes to the vdW force, observable via its local exponent dlog(F)/dlog(D). For large separations D ?10 nm, where only the ?z vdW forces remain, we find that the Gr-Gr vdW interaction is substantially reduced from the RPA prediction. Its D dependence is very sensitive to the form of the long-wavelength, in-plane many-body enhancement of the velocity of the massless Dirac fermions and may provide independent confirmation of the latter via direct force measurements. The simple connection that we expose is a strong motivation for further refinement of recent successful direct vdW force measurements.

Dobson, John F.; Gould, Tim; Vignale, Giovanni

2014-04-01

267

A charge optimized many-body potential for titanium nitride (TiN).

This work presents a new empirical, variable charge potential for TiN systems in the charge-optimized many-body potential framework. The potential parameters were determined by fitting them to experimental data for the enthalpy of formation, lattice parameters, and elastic constants of rocksalt structured TiN. The potential does a good job of describing the fundamental physical properties (defect formation and surface energies) of TiN relative to the predictions of first-principles calculations. This potential is used in classical molecular dynamics simulations to examine the interface of fcc-Ti(0 0 1)/TiN(0 0 1) and to characterize the adsorption of oxygen atoms and molecules on the TiN(0 0 1) surface. The results indicate that the potential is well suited to model TiN thin films and to explore the chemistry associated with their oxidation. PMID:24903100

Cheng, Y-T; Liang, T; Martinez, J A; Phillpot, S R; Sinnott, S B

2014-07-01

268

Electronic excitations of bulk LiCl from many-body perturbation theory.

We present the quasiparticle band structure and the optical excitation spectrum of bulk LiCl, using many-body perturbation theory. Density-functional theory is used to calculate the ground-state geometry of the system. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into consideration, electron-hole pair states and optical excitations are obtained by solving the Bethe-Salpeter equation for the electron-hole two-particle Green function. The calculated band gap is 9.5 eV, which is in good agreement with the experimental result of 9.4 eV. And the calculated optical absorption spectrum, which contains an exciton peak at 8.8 eV and a resonant-exciton peak at 9.8 eV, is also in good agreement with experimental data. PMID:24320397

Jiang, Yun-Feng; Wang, Neng-Ping; Rohlfing, Michael

2013-12-01

269

Probing Real-Space and Time-Resolved Correlation Functions with Many-Body Ramsey Interferometry

NASA Astrophysics Data System (ADS)

We propose to use Ramsey interferometry and single-site addressability, available in synthetic matter such as cold atoms or trapped ions, to measure real-space and time-resolved spin correlation functions. These correlation functions directly probe the excitations of the system, which makes it possible to characterize the underlying many-body states. Moreover, they contain valuable information about phase transitions where they exhibit scale invariance. We also discuss experimental imperfections and show that a spin-echo protocol can be used to cancel slow fluctuations in the magnetic field. We explicitly consider examples of the two-dimensional, antiferromagnetic Heisenberg model and the one-dimensional, long-range transverse field Ising model to illustrate the technique.

Knap, Michael; Kantian, Adrian; Giamarchi, Thierry; Bloch, Immanuel; Lukin, Mikhail D.; Demler, Eugene

2013-10-01

270

We formulate and study, in general terms, the problem of quantum system identification, i.e., the determination (or estimation) of unknown quantum channels through their action on suitably chosen input density operators. We also present a quantitative analysis of the worst-case performance of these schemes.

Maxim Raginsky

2003-06-02

271

The aim of quantum system identification is to estimate the ingredients inside a black box, in which some quantum-mechanical unitary process takes place, by just looking at its input-output behavior. Here we establish a basic and general framework for quantum system identification, that allows us to classify how much knowledge about the quantum system is attainable, in principle, from a given experimental setup. Prior knowledge on some elements of the black box helps the system identification. We present an example in which a Bell measurement is more efficient to identify the system. When the topology of the system is known, the framework enables us to establish a general criterion for the estimability of the coupling constants in its Hamiltonian.

Daniel Burgarth; Kazuya Yuasa

2011-04-04

272

A secure quantum identification system combining a classical identification procedure and quantum key distribution is proposed. Each identification sequence is always used just once and new sequences are ``refuelled'' from a shared provably secret key transferred through the quantum channel. Two identification protocols are devised. The first protocol can be applied when legitimate users have an unjammable public channel at their disposal. The deception probability is derived for the case of a noisy quantum channel. The second protocol employs unconditionally secure authentication of information sent over the public channel, and thus it can be applied even in the case when an adversary is allowed to modify public communications. An experimental realization of a quantum identification system is described.

Miloslav Dusek; Ondrej Haderka; Martin Hendrych; Robert Myska

1998-09-10

273

Local Conservation Laws and the Structure of the Many-Body Localized States

We construct a complete set of local integrals of motion that characterize the many-body localized (MBL) phase. Our approach relies on the assumption that local perturbations act locally on the eigenstates in the MBL phase, ...

Serbyn, Maksym

274

Dynamical and statistical modelling of many body collisions Part II: Energy exchange

While rarefied gas dynamics has traditionally assumed a dilute gas, whose densities are so low that only binary collisions and single-body gas surface interactions occur, expressions for many-body collision rates and for many-body gas surface interaction (GSI) rates seem to suggest that at lower heights the dilute gas is not valid. In particular, in the pure rarefied regime, two-body GSIs

A. A. Agbormbai

2001-01-01

275

Dynamical and statistical modelling of many body collisions Part I: Scattering

Although rarefied gas dynamics has traditionally rested on the dilute gas assumption, which presupposes that only binary collisions and single-body gas surface interactions occur, expressions for many-body collision rates and for many-body gas surface interaction (GSI) rates seem to suggest that at lesser heights the dilute gas assumption is not valid. In particular, in the pure rarefied regime, two-body GSIs

A. A. Agbormbai

2001-01-01

276

Many-body forces and electron correlation in small metal clusters

The many-body decomposition of the interaction energy for BeN and LiN (N=2 to 4) clusters is calculated in two approximations: the self-consistent-field method and the Mo\\/ller-Plesset perturbation theory up to the fourth order. This allows us to estimate the electron-correlation contributions to the many-body forces. The explicit expressions for these contributions in the perturbation theory formalism are obtained. We present

Ilya G. Kaplan; Jorge Hernández-Cobos; Iván Ortega-Blake; Octavio Novaro

1996-01-01

277

The major scientific achievements that have resulted from the contract are briefly outlined. These include significant progress in the understanding of the Kondo effect, the magnetic behavior of less dilute alloys, fundamental studies of magnetism in metals, quantum chemistry of pseudopotential methods, amorphous materials, and miscellaneous many-body problems. A list of the primary papers is included.

1972-01-01

278

Numerical Analysis of Coherent Many-Body Currents in a Single Atom Transistor

We study the dynamics of many atoms in the recently proposed Single Atom Transistor setup [A. Micheli, A. J. Daley, D. Jaksch, and P. Zoller, Phys. Rev. Lett. 93, 140408 (2004)] using recently developed numerical methods. In this setup, a localised spin 1/2 impurity is used to switch the transport of atoms in a 1D optical lattice: in one state the impurity is transparent to probe atoms, but in the other acts as a single atom mirror. We calculate time-dependent currents for bosons passing the impurity atom, and find interesting many body effects. These include substantially different transport properties for bosons in the strongly interacting (Tonks) regime when compared with fermions, and an unexpected decrease in the current when weakly interacting probe atoms are initially accelerated to a non-zero mean momentum. We also provide more insight into the application of our numerical methods to this system, and discuss open questions about the currents approached by the system on long timescales.

A. J. Daley; S. R. Clark; D. Jaksch; P. Zoller

2005-06-29

279

Optically Engineered Quantum States in Ultrafast and Ultracold Systems

NASA Astrophysics Data System (ADS)

This short account summarizes our recent achievements in ultrafast coherent control of isolated molecules in the gas phase, and its ongoing applications to an ensemble of ultracold Rydberg atoms to explore quantum many-body dynamics.

Ohmori, Kenji

2014-08-01

280

The Role of Many-Body Dispersion Interactions in Molecular Crystals

NASA Astrophysics Data System (ADS)

The structure, energetics, and electronic properties of molecular crystals are studied using density functional theory (DFT) with the recently developed many-body dispersion (MBD) method [Tkatchenko et al. Phys. Rev. Lett. 108, 236402 (2012)]. It is shown that accounting for the long-range electrostatic screening in extended systems is essential for obtaining the correct dielectric constants and ensuing optical properties of molecular crystals [Schatschneider et al., arXiv:1211.1683]. Furthermore, accounting for the non-additive many-center dispersion interactions is crucial for obtaining a highly accurate description of the energetics of molecular crystals. This includes lattice energies, sublimation enthalpies [Reilly et al., to be published], and relative stabilities of polymorphs [Marom et al. arXiv: 1210.5636] [4pt] In collaboration with Leslie Leiserowitz, Weizmann Institute of Science, Israel; Bohdan Schatschneider, The Pennsylvania State University, Fayette; Robert DiStasio, Princeton University; Anthony Reilly and Guo-Xu Zhang, Fritz Haber Institute of the Max Planck Society, Berlin; James Chelikowsky, The University of Texas at Austin; and Alexandre Tkatchenko, Fritz Haber Institute of the Max Planck Society, Berlin.

Marom, Noa

2013-03-01

281

PROGRAPE-1: A Programmable, Multi-Purpose Computer for Many-Body Simulations

We have developed PROGRAPE-1 (PROgrammable GRAPE-1), a programmable multi-purpose computer for many-body simulations. The main difference between PROGRAPE-1 and "traditional" GRAPE systems is that the former uses FPGA (Field Programmable Gate Array) chips as the processing elements, while the latter rely on the hardwired pipeline processor specialized to gravitational interactions. Since the logic implemented in FPGA chips can be reconfigured, we can use PROGRAPE-1 to calculate not only gravitational interactions but also other forms of interactions such as van der Waals force, hydrodynamical interactions in SPH calculation and so on. PROGRAPE-1 comprises two Altera EPF10K100 FPGA chips, each of which contains nominally 100,000 gates. To evaluate the programmability and performance of PROGRAPE-1, we implemented a pipeline for gravitational interaction similar to that of GRAPE-3. One pipeline fitted into a single FPGA chip, which operated at 16 MHz clock. Thus, for gravitational interaction, PROGRAPE-1 provided the speed of 0.96 Gflops-equivalent. PROGRAPE will prove to be useful for wide-range of particle-based simulations in which the calculation cost of interactions other than gravity is high, such as the evaluation of SPH interactions.

Tsuyoshi Hamada; Toshiyuki Fukushige; Atsushi Kawai; Junichiro Makino

1999-06-25

282

A charge optimized many-body (COMB) potential for titanium and titania.

This work proposes an empirical, variable charge potential for Ti and TiO(2) systems based on the charge-optimized many-body (COMB) potential framework. The parameters of the potential function are fit to the structural and mechanical properties of the Ti hcp phase, the TiO(2) rutile phase, and the energetics of polymorphs of both Ti and TiO(2). The relative stabilities of TiO(2) rutile surfaces are predicted and compared to the results of density functional theory (DFT) and empirical potential calculations. The transferability of the developed potential is demonstrated by determining the adsorption energy of Cu clusters of various sizes on the rutile TiO(2)(1?1?0) surface using molecular dynamics simulations. The results indicate that the adsorption energy is dependent on the number of Cu-Cu bonds and Cu-O bonds formed at the Cu/TiO(2) interface. The adsorption energies of Cu clusters on the reduced and oxidized TiO(2)(1?1?0) surfaces are also investigated, and the COMB potential predicts enhanced bonding between Cu clusters and the oxidized surface, which is consistent with both experimental observations and the results of DFT calculations for other transition metals (Au and Ag) on this oxidized surface. PMID:24943265

Cheng, Yu-Ting; Shan, Tzu-Ray; Liang, Tao; Behera, Rakesh K; Phillpot, Simon R; Sinnott, Susan B

2014-08-01

283

Extended many-body potential of Hauschild and Prausnitz for pure HFD-like fluids

NASA Astrophysics Data System (ADS)

We have extended the many-body potential of Hauschild and Prausnitz (1993) in terms of the non-additivity coefficient and density (at different temperatures from liquid phase to supercritical region) for pure fluids. In order to compare our many-body potential with the accurate three-body potentials in the literature, we have performed molecular dynamics simulation to obtain pressure and self-diffusion coefficient values at different temperatures and densities using the two-body HFD-like potential and different three-body potentials. Our results indicated that our extended many-body potential is superior to the three-body potential of Guzman et al. (2011) for the different fluids and is also better than the three-body potential of Wang and Sadus (2006) for some noble gases.

Abbaspour, Mohsen; Naderkhovy, Nasrin

2014-11-01

284

Many-body Propagator Theory with Three-Body Interactions: a Path to Exotic Open Shell Isotopes

NASA Astrophysics Data System (ADS)

Ab-initio predictions of nuclei with masses up to A~100 or more are becoming possible thanks to novel advances in computations and in the formalism of many-body physics. Some of the most fundamental issues include how to deal with many-nucleon interactions, how to calculate degenerate—open shell—systems, and pursuing ab-initio approaches to reaction theory. Self-consistent Green's function (SCGF) theory is a natural approach to address these challenges. Its formalism has recently been extended to three- and many-body interactions and reformulated within the Gorkov framework to reach semi-magic open shell isotopes. These exciting developments, together with the predictive power of chiral nuclear Hamiltonians, are opening the path to understanding large portions of the nuclear chart, especially within the sd and pf shells. The present talk reviews the most recent advances in ab-initio nuclear structure and many-body theory that have been possible through the SCGF approach.

Barbieri, C.

2014-08-01

285

Many-body Propagator Theory with Three-Body Interactions: a Path to Exotic Open Shell Isotopes

Ab-initio predictions of nuclei with masses up to A~100 or more is becoming possible thanks to novel advances in computations and in the formalism of many-body physics. Some of the most fundamental issues include how to deal with many-nucleon interactions, how to calculate degenerate--open shell--systems, and pursuing ab-initio approaches to reaction theory. Self-consistent Green's function (SCGF) theory is a natural approach to address these challenges. Its formalism has recently been extended to three- and many-body interactions and reformulated within the Gorkov framework to reach semi-magic open shell isotopes. These exciting developments, together with the predictive power of chiral nuclear Hamiltonians, are opening the path to understanding large portions of the nuclear chart, especially within the $sd$ and $pf$ shells. The present talk reviews the most recent advances in ab-initio nuclear structure and many-body theory that have been possible through the SCGF approach.

C. Barbieri

2014-05-12

286

Short-time-evolved wave functions for solving quantum many-body problems

converges essentially to the exact ground state in a relatively short time. Thus a short-time evolved wave function can be an excellent approximation to the exact ground state. Such a short-time-evolved wave function can be obtained by factorizing...

Ciftja, O.; Chin, Siu A.

2003-01-01

287

Fourth-order diffusion Monte Carlo algorithms for solving quantum many-body problems

higher derivatives of the drift velocity and local energy and are more complicated to program. However, they allowed very large time steps to be used, converged faster with lesser correlations, and virtually eliminated the step size error. We demonstrated...

Forbert, HA; Chin, Siu A.

2001-01-01

288

Some considerations about the importance of coherence effects for bremsstrahlung processes in non-equilibrium dense matter (Landau - Pomeranchuk - Migdal - ef- fect) are presented. They are of particular relevance for the application to photon - and di-lepton production from high energy nuclear collisions, to gluon radiation in QCD transport, or parton kinetics and to neutrino and axion radiation from

Jorn Knoll; Dmitri N. Voskresensky

1995-01-01

289

Transitionless quantum driving in open quantum systems

NASA Astrophysics Data System (ADS)

We extend the concept of superadiabatic dynamics, or transitionless quantum driving, to quantum open systems whose evolution is governed by a master equation in the Lindblad form. We provide the general framework needed to determine the control strategy required to achieve superadiabaticity. We apply our formalism to two examples consisting of a two-level system coupled to environments with time-dependent bath operators.

Vacanti, G.; Fazio, R.; Montangero, S.; Palma, G. M.; Paternostro, M.; Vedral, V.

2014-05-01

290

Many-body effects in electron liquids with Rashba spin-orbit coupling

The main topic of the present thesis is represented by the many-body effects which characterize the physical behavior of an electron liquid in various realizations. We begin by studying the problem of the response of an otherwise homogeneous electron liquid to the potential of an impurity embedded in its bulk. The most dramatic consequence of this perturbation is the existence

George E. Simion

2006-01-01

291

Gauge transformations to combine multi-component many-body interatomic potentials

Many-body interatomic potentials play an important role in atomistic modelling of materials. For pure elements it is known that there exist gauge transformations that can change the form of the potential functions without modifying its properties. These same transformations, however, fail when applied to alloys. Even though different research groups may use the same potentials to describe pure elements, the

G. Bonny; R. C. Pasianot

2010-01-01

292

N=2 superconformal Newton-Hooke algebra and many-body mechanics

NASA Astrophysics Data System (ADS)

A representation of the conformal Newton-Hooke algebra on a phase space of n particles in arbitrary dimension which interact with one another via a generic conformal potential and experience a universal cosmological repulsion or attraction is constructed. The minimal N=2 superconformal extension of the Newton-Hooke algebra and its dynamical realization in many-body mechanics are studied.

Galajinsky, Anton

2009-10-01

293

Matter Wave Optical Techniques for Probing Many-body Scott Nicholas Sanders

Matter Wave Optical Techniques for Probing Many-body Targets by Scott Nicholas Sanders A by . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thomas Greytak Chairman, Department Committee on Graduate Theses #12;#12;to my family #12;#12;Matter Wave of Philosophy in Physics Abstract This thesis reports on our investigation of the uses of matter waves to probe

Heller, Eric

294

Energy density matrix formalism for interacting quantum systems: a quantum Monte Carlo study

We develop an energy density matrix that parallels the one-body reduced density matrix (1RDM) for many-body quantum systems. Just as the density matrix gives access to the number density and occupation numbers, the energy density matrix yields the energy density and orbital occupation energies. The eigenvectors of the matrix provide a natural orbital partitioning of the energy density while the eigenvalues comprise a single particle energy spectrum obeying a total energy sum rule. For mean-field systems the energy density matrix recovers the exact spectrum. When correlation becomes important, the occupation energies resemble quasiparticle energies in some respects. We explore the occupation energy spectrum for the finite 3D homogeneous electron gas in the metallic regime and an isolated oxygen atom with ground state quantum Monte Carlo techniques implemented in the QMCPACK simulation code. The occupation energy spectrum for the homogeneous electron gas can be described by an effective mass below the Fermi lev...

Krogel, Jaron T; Reboredo, Fernando A

2014-01-01

295

Nonlinear brain dynamics as macroscopic manifestation of underlying many-body field dynamics

Neural activity patterns related to behavior occur at many scales in time and space from the atomic and molecular to the whole brain. Here we explore the feasibility of interpreting neurophysiological data in the context of many-body physics by using tools that physicists have devised to analyze comparable hierarchies in other fields of science. We focus on a mesoscopic level that offers a multi-step pathway between the microscopic functions of neurons and the macroscopic functions of brain systems revealed by hemodynamic imaging. We use electroencephalographic (EEG) records collected from high-density electrode arrays fixed on the epidural surfaces of primary sensory and limbic areas in rabbits and cats trained to discriminate conditioned stimuli (CS) in the various modalities. High temporal resolution of EEG signals with the Hilbert transform gives evidence for diverse intermittent spatial patterns of amplitude (AM) and phase modulations (PM) of carrier waves that repeatedly re-synchronize in the beta and gamma ranges at near zero time lags over long distances. The dominant mechanism for neural interactions by axodendritic synaptic transmission should impose distance-dependent delays on the EEG oscillations owing to finite propagation velocities. It does not. EEGs instead show evidence for anomalous dispersion: the existence in neural populations of a low velocity range of information and energy transfers, and a high velocity range of the spread of phase transitions. This distinction labels the phenomenon but does not explain it. In this report we explore the analysis of these phenomena using concepts of energy dissipation, the maintenance by cortex of multiple ground states corresponding to AM patterns, and the exclusive selection by spontaneous breakdown of symmetry (SBS) of single states in sequences.

Walter J. Freeman; Giuseppe Vitiello

2005-11-22

296

Quantum Cybernetics and Complex Quantum Systems Science - A Quantum Connectionist Exploration

Quantum cybernetics and its connections to complex quantum systems science is addressed from the perspective of complex quantum computing systems. In this way, the notion of an autonomous quantum computing system is introduced in regards to quantum artificial intelligence, and applied to quantum artificial neural networks, considered as autonomous quantum computing systems, which leads to a quantum connectionist framework within quantum cybernetics for complex quantum computing systems. Several examples of quantum feedforward neural networks are addressed in regards to Boolean functions' computation, multilayer quantum computation dynamics, entanglement and quantum complementarity. The examples provide a framework for a reflection on the role of quantum artificial neural networks as a general framework for addressing complex quantum systems that perform network-based quantum computation, possible consequences are drawn regarding quantum technologies, as well as fundamental research in complex quantum systems science and quantum biology.

Carlos Pedro Gonçalves

2014-02-05

297

Quantum algorithm in quantum network systems

Recently, the quantum computer (QC) using the nano-devices have significantly attracted attention, because a large-scale extention of the qubits could be easily realized in the nano-devices. However, some problems for the realization of the QC with nano-devices arise from the short decoherence time and the interaction of qubits only between nearest-neighbor qubits. Therefore, we try to design the optimal quantum circuit of the quantum Fourier transform in various network system by means of the genetic algorithm (GA)

Sakamoto, I.; Yamaguchi, T.; Nagao, H.; Nishikawa, K. [Department of Computational Science, Faculty of Science, Kanazawa University, Kakuma, Kanazawa, 920-1192 (Japan)

2004-04-30

298

Quantum dephasing of a two-state system by a nonequilibrium harmonic oscillator

NASA Astrophysics Data System (ADS)

In this paper, we investigate coherent quantum dynamics in a nonequilibrium environment. We focus on a two-state quantum system strongly coupled to a single classical environmental oscillator, and explore the effect of nonstationary statistical properties of the oscillator on the quantum evolution. A simple nonequilibrium model, consisting of an oscillator with a well-defined initial phase which undergoes subsequent diffusion, is introduced and studied. Approximate but accurate analytic expressions for the evolution of the off-diagonal density matrix element of the quantum system are derived in the second-order cumulant approximation. The effect of the initial phase choice on the subsequent quantum evolution is quantified. It is observed that the initial phase can have a significant effect on the preservation of coherence on short time scales, suggesting this variable as a control parameter for optimizing coherence in many-body quantum systems.

Martens, Craig C.

2013-07-01

299

NASA Astrophysics Data System (ADS)

An efficient, monomer-based electronic structure method is introduced for computing non-covalent interactions in molecular and ionic clusters. It builds upon our ``explicit polarization" (XPol) with pairwise-additive symmetry-adapted perturbation theory (SAPT) using the Kohn-Sham (KS) version of SAPT, but replaces the problematic and expensive sum-over-states dispersion terms with empirical potentials. This modification reduces the scaling from {O}(N^5) to {O}(N^3) and also facilitates the use of Kohn-Sham density functional theory (KS-DFT) as a low-cost means to capture intramolecular electron correlation. Accurate binding energies are obtained for benchmark databases of dimer binding energies, and potential energy curves are also captured accurately, for a variety of challenging systems. As compared to traditional DFT-SAPT or SAPT(DFT) methods, it removes the limitation to dimers and extends SAPT-based methodology to many-body systems. For many-body systems such as water clusters and halide-water cluster anions, the new method is superior to established density-functional methods for non-covalent interactions. We suggest that using different asymptotic corrections for different monomers is necessary to get good binding energies in general, as DFT-SAPT or SAPT(DFT), especially for hydrogen-bonded complexes. We also introduce a decomposition scheme for the interaction energy that extends traditional SAPT energy decomposition analysis to systems containing more than two monomers, and we find that the various energy components (electrostatic, exchange, induction, and dispersion) are in very good agreement with high-level SAPT benchmarks for dimers. For (H_2O)_6, the many-body contribution to the interaction energy agrees well with that obtained from traditional Kitaura-Morokuma energy decomposition analysis.

Lao, Ka Un; Herbert, John M.

2013-06-01

300

Many-body theory for angular resolved photoelectron spectra of metal clusters

Angular resolved photoelectron spectra of metal clusters have been experimentally measured for the first time only recently. These measurements have been performed systematically for sodium clusters in a broad range of cluster sizes. This work attracted a lot of attention and was reported practically at all major international cluster conferences because it revealed a very non-trivial behavior of the angular anisotropy parameter with respect to photon energy and provided a method for probing the angular momentum character of the valence orbitals of free nanoclusters. Initial attempts to explain these observations within single particle approximations fail completely. In this Letter we present a consistent many-body theory for the description of angular resolved photoelectron spectra of metal clusters. Jellium model formalism is employed. Our calculations demonstrate the dominant role of the many-body effects in the formation of angular distributions of photoelectrons emitted from sodium clusters and are in a ...

Solov'yov, Andrey V; Ivanov, Vadim K

2009-01-01

301

The hierarchy of multiple many-body interaction scales in high-temperature superconductors

To date, angle-resolved photoemission spectroscopy has been successful in identifying energy scales of the many-body interactions in correlated materials, focused on binding energies of up to a few hundred meV below the Fermi energy. Here, at higher energy scale, we present improved experimental data from four families of high-T{sub c} superconductors over a wide doping range that reveal a hierarchy of many-body interaction scales focused on: the low energy anomaly ('kink') of 0.03-0.09eV, a high energy anomaly of 0.3-0.5eV, and an anomalous enhancement of the width of the LDA-based CuO{sub 2} band extending to energies of {approx} 2 eV. Besides their universal behavior over the families, we find that all of these three dispersion anomalies also show clear doping dependence over the doping range presented.

Meevasana, W.

2010-05-03

302

A time-independent many-body Rayleigh-Schrödinger perturbation theory is developed for total energy functionals, which depend simultaneously on a wave function and on the associated electron density. The most prominent example of such functionals is the Kohn-Sham energy functional, but similar situations occur as well in quantum chemical solvent effect theories. In contrast to previous density-functional perturbation theories, formulated in terms of

János G. Ángyán

2008-01-01

303

Relaxation, Polarization, and Other Many-Body Effects in the Photoionization of Atoms

Inner-shell photoionization of lithium, xenon, and barium is investigated using the many-body perturbation theory (MBPT) and a variant of the relativistic random -phase approximation (RRPA) which includes relaxation effects. Particular attention is given to the higher-order effects of relaxation and polarization of the ionic cores that remain following the ionization. Other notable effects such as interchannel coupling, photoionization with excitation

Mickey Dean Kutzner

1989-01-01

304

Nature of stability of Mg 4 and many-body forces

The precise ab initio calculations of the tetramer Mg4 were performed at the all-electron CCSD(T)\\/aug-cc-pVQZ level. The dissociation energy in respect to all possible dissociation channels at different levels of accuracy, from SCF till CCSD(T), but with the same large basis set, was calculated. Except the SCF method, in all approximations Mg4 was found stable. The many-body decomposition of the

C. C. Díaz-Torrejón; F. Espinosa-Magaña; Ilya G. Kaplan

2010-01-01

305

Many-body forces and stability of the alkaline-earth tetramers

The comparative study of the interaction energy and its many-body decomposition for Be4, Mg4, and Ca4 at the all-electron CCSD(T)\\/aug-cc-pVQZ level is performed. For study of dependence of the binding energy and the orbital population on the cluster size the corresponding dimers and trimers were also calculated at the same level of theory. In comparison with weakly bound dimers, the

C. C. Díaz-Torrejón; Ilya G. Kaplan

2011-01-01

306

Many-body energy decomposition of hydrogen-bonded glycine clusters in gas-phase

A detailed analysis of the many-body contribution to the interaction energies of the gas-phase hydrogen-bonded glycine clusters, (Gly)N, N=1–4 is presented. The energetics of the hydrogen-bonded dimer, trimer and tetramer complexes have been analyzed using density-functional theory. The magnitude of the two- through four-body energy terms have been calculated and compared. The relaxation energy and the two-body energy terms are

Puspitapallab Chaudhuri; Sylvio Canuto

2010-01-01

307

Many-body energy decomposition analysis of cooperativity in hydrogen fluoride clusters

This article studies the cooperativity present in hydrogen fluoride clusters, (FH)n, by means of a many-body decomposition of the binding energy. With the aim of quantifying how the results depend on the calculation level, the partition was performed from dimer to hexamer at the RHF, MP2, and density functional (B3LYP) levels, and for the heptamer and octamer at the RHF

Luis Rincón; Rafael Almeida; David García Aldea

2005-01-01

308

Detecting many-body entanglement in noninteracting ultracold atomic Fermi gases

We explore the possibility of detecting many-body entanglement using time-of-flight (TOF) momentum correlations in ultracold atomic Fermi gases. In analogy to the vacuum correlations responsible for Bekenstein-Hawking black hole entropy, a partitioned atomic gas will exhibit particle-hole correlations responsible for entanglement entropy. The signature of these momentum correlations might be detected by a sensitive TOF-type experiment.

Levine, G. C.; Bantegui, M. J. [Department of Physics and Astronomy, Hofstra University, Hempstead, New York 11549 (United States); Friedman, B. A. [Department of Physics, Sam Houston State University, Huntsville, Texas 77341 (United States)

2011-01-15

309

Quantum critical dynamics of the boson system in the Ginzburg-Landau model

NASA Astrophysics Data System (ADS)

The quantum critical dynamics of the quantum phase transitions is considered. In the framework of the unified theory, based on the Keldysh technique, we consider the crossover from the classical to the quantum description of the boson many-body system dynamics close to the second order quantum phase transition. It is shown that in this case the upper critical space dimension of this model is dc+=2, therefore the quantum critical dynamics approach is useful in case of d<2. In the one-dimension system the phase coherence time does diverge at the quantum critical point, gc, and has the form of ??-ln?g-gc?/?g-gc?, the correlation radius diverges as rc??g-gc?(?=0.6).

Vasin, M. G.

2014-12-01

310

Topology, localization, and quantum information in atomic, molecular and optical systems

NASA Astrophysics Data System (ADS)

The scientific interface between atomic, molecular and optical (AMO) physics, condensed matter, and quantum information science has recently led to the development of new insights and tools that bridge the gap between macroscopic quantum behavior and detailed microscopic intuition. While the dialogue between these fields has sharpened our understanding of quantum theory, it has also raised a bevy of new questions regarding the out-of-equilibrium dynamics and control of many-body systems. This thesis is motivated by experimental advances that make it possible to produce and probe isolated, strongly interacting ensembles of disordered particles, as found in systems ranging from trapped ions and Rydberg atoms to ultracold polar molecules and spin defects in the solid state. The presence of strong interactions in these systems underlies their potential for exploring correlated many-body physics and this thesis presents recent results on realizing fractionalization and localization. From a complementary perspective, the controlled manipulation of individual quanta can also enable the bottom-up construction of quantum devices. To this end, this thesis also describes blueprints for a room-temperature quantum computer, quantum credit cards and nanoscale quantum thermometry.

Yao, Norman Ying

311

Multi-scale Extensions to Quantum Cluster Methods for Strongly Correlated Electron Systems

A numerically implementable Multi-scale Many-Body approach to strongly correlated electron systems is introduced. An extension to quantum cluster methods, it approximates correlations on any given length-scale commensurate with the strength of the correlations on the respective scale. Short length-scales are treated explicitly, long ones are addressed at a mean-field level and intermediate length-regime correlations are assumed to be weak and

C. Slezak; M. Jarrell; Th. Maier; J. Deisz

2006-01-01

312

Multi-scale extensions to quantum cluster methods for strongly correlated electron systems

A numerically implementable multi-scale many-body approach to strongly correlated electron systems is introduced. An extension to quantum cluster methods, it approximates correlations on any given length-scale commensurate with the strength of the correlations on the respective scale. Short length-scales are treated explicitly, long ones are addressed at a dynamical mean-field level and intermediate length-regime correlations are assumed to be weak

Cyrill Slezak; Mark Jarrell; Thomas A Maier; John Deisz

2009-01-01

313

NASA Astrophysics Data System (ADS)

We investigate charge transfer in prototypical molecular donor-acceptor compounds using hybrid density functional theory (DFT) and the GW approximation at the perturbative level (G0W0) and at full self-consistency (sc-GW). For the systems considered here, no charge transfer should be expected at large intermolecular separation according to photoemission experiments and accurate quantum-chemistry calculations. The capability of hybrid exchange-correlation functionals of reproducing this feature depends critically on the fraction of exact exchange ?, as for small values of ? spurious fractional charge transfer is observed between the donor and the acceptor. G0W0 based on hybrid DFT yields the correct alignment of the frontier orbitals for all values of ?. However, G0W0 has no capacity to alter the ground-state properties of the system because of its perturbative nature. The electron density in donor-acceptor compounds thus remains incorrect for small ? values. In sc-GW, where the Green's function is obtained from the iterative solution of the Dyson equation, the electron density is updated and reflects the correct description of the level alignment at the GW level, demonstrating the importance of self-consistent many-body approaches for the description of ground- and excited-state properties in donor-acceptor systems.

Caruso, Fabio; Atalla, Viktor; Ren, Xinguo; Rubio, Angel; Scheffler, Matthias; Rinke, Patrick

2014-08-01

314

Collective edge modes in fractional quantum Hall systems

NASA Astrophysics Data System (ADS)

Over the past few years one of us (Murthy) in collaboration with Shankar has developed an extended Hamiltonian formalism capable of describing the ground-state and low-energy excitations in the fractional quantum Hall regime. The Hamiltonian, expressed in terms of composite fermion operators, incorporates all the nonperturbative features of the fractional Hall regime, so that conventional many-body approximations such as Hartree-Fock and time-dependent Hartree-Fock are applicable. We apply this formalism to develop a microscopic theory of the collective edge modes in fractional quantum Hall regime. We present the results for edge mode dispersions at principal filling factors ?=1/3 , 1/5 , and 2/5 for systems with unreconstructed edges. The primary advantage of the method is that one works in the thermodynamic limit right from the beginning, thus avoiding the finite-size effects which ultimately limit exact diagonalization studies.

Nguyen, Hoang K.; Joglekar, Yogesh N.; Murthy, Ganpathy

2004-07-01

315

Efficient free energy calculations of quantum systems through computer simulations

NASA Astrophysics Data System (ADS)

In general, the classical limit is assumed in computer simulation calculations of free energy. This approximation, however, is not justifiable for a class of systems in which quantum contributions for the free energy cannot be neglected. The inclusion of quantum effects is important for the determination of reliable phase diagrams of these systems. In this work, we present a new methodology to compute the free energy of many-body quantum systems [1]. This methodology results from the combination of the path integral formulation of statistical mechanics and efficient non-equilibrium methods to estimate free energy, namely, the adiabatic switching and reversible scaling methods. A quantum Einstein crystal is used as a model to show the accuracy and reliability the methodology. This new method is applied to the calculation of solid-liquid coexistence properties of neon. Our findings indicate that quantum contributions to properties such as, melting point, latent heat of fusion, entropy of fusion, and slope of melting line can be up to 10% of the calculated values using the classical approximation. [1] R. M. Ramirez, C. P. Herrero, A. Antonelli, and E. R. Hernández, Journal of Chemical Physics 129, 064110 (2008)

Antonelli, Alex; Ramirez, Rafael; Herrero, Carlos; Hernandez, Eduardo

2009-03-01

316

DPS Quantum Key Distribution System

Differential-phase-shift (DPS) quantum key distribution (QKD) is one scheme of quantum key distribution whose security is based on the quantum nature of lightwave. This protocol features simplicity, a high key creation rate, and robustness against photon-number-splitting attacks. We describe DPS-QKD in this paper, including its setup and operation, eavesdropping against DPS-QKD, system performance, and modified systems to improve the system

Kyo Inoue

2010-01-01

317

Two novel classes of solvable many-body problems of goldfish type with constraints

NASA Astrophysics Data System (ADS)

Two novel classes of many-body models with nonlinear interactions 'of goldfish type' are introduced. They are solvable provided the initial data satisfy a single constraint (in one case; in the other, two constraints), i.e., for such initial data the solution of their initial-value problem can be achieved via algebraic operations, such as finding the eigenvalues of given matrices or equivalently the zeros of known polynomials. Entirely isochronous versions of some of these models are also exhibited, i.e., versions of these models whose nonsingular solutions are all completely periodic with the same period.

Calogero, F.; Gómez-Ullate, D.

2007-05-01

318

Communication: Dominance of extreme statistics in a prototype many-body Brownian ratchet

NASA Astrophysics Data System (ADS)

Many forms of cell motility rely on Brownian ratchet mechanisms that involve multiple stochastic processes. We present a computational and theoretical study of the nonequilibrium statistical dynamics of such a many-body ratchet, in the specific form of a growing polymer gel that pushes a diffusing obstacle. We find that oft-neglected correlations among constituent filaments impact steady-state kinetics and significantly deplete the gel's density within molecular distances of its leading edge. These behaviors are captured quantitatively by a self-consistent theory for extreme fluctuations in filaments' spatial distribution.

Hohlfeld, Evan; Geissler, Phillip L.

2014-10-01

319

Correlations in a Many-Body Calculation of $^{\\bf 11}$Li

A many-body calculation of $^{11}$Li is presented where the only input is the well-tested, finite-range {\\it D1S} effective interaction of {\\it Gogny}. Pairing correlations are included in a constrained Hartree-Fock-Bogolyubov calculation, while long-range collective correlations are introduced using a GCM derived calculation. Correlations are found to play an important role in describing $^{11}$Li. A substantive underlying $^9$Li core of $^{11}$Li is found, which has a different density profile than a free $^9$Li nucleus. This may have significant implications in the use of a three-body framework in studies of $^{11}$Li.

C. R. Chinn; J. Dechargé; J. -F. Berger

1994-10-19

320

Control of open quantum systems

This thesis describes the development, investigation and experimental implementation via liquid state nuclear magnetic resonance techniques of new methods for controlling open quantum systems. First, methods that improve ...

Boulant, Nicolas

2005-01-01

321

Hamiltonian quantum simulation with bounded-strength controls

We propose dynamical control schemes for Hamiltonian simulation in many-body quantum systems that avoid instantaneous control operations and rely solely on realistic bounded-strength control Hamiltonians. Each simulation ...

Bookatz, Adam D.

322

Scale-adaptive tensor algebra for local many-body methods of electronic structure theory

While the formalism of multiresolution analysis (MRA), based on wavelets and adaptive integral representations of operators, is actively progressing in electronic structure theory (mostly on the independent-particle level and, recently, second-order perturbation theory), the concepts of multiresolution and adaptivity can also be utilized within the traditional formulation of correlated (many-particle) theory which is based on second quantization and the corresponding (generally nonorthogonal) tensor algebra. In this paper, we present a formalism called scale-adaptive tensor algebra (SATA) which exploits an adaptive representation of tensors of many-body operators via the local adjustment of the basis set quality. Given a series of locally supported fragment bases of a progressively lower quality, we formulate the explicit rules for tensor algebra operations dealing with adaptively resolved tensor operands. The formalism suggested is expected to enhance the applicability and reliability of local correlated many-body methods of electronic structure theory, especially those directly based on atomic orbitals (or any other localized basis functions).

Liakh, Dmitry I [ORNL] [ORNL

2014-01-01

323

A Relativistic Many-Body Analysis of the Electric Dipole Moment of $^{223}$Rn

We report the results of our {\\it ab initio} relativistic many-body calculations of the electric dipole moment (EDM) $d_A$ arising from the electron-nucleus tensor-pseudotensor (T-PT) interaction, the interaction of the nuclear Schiff moment (NSM) with the atomic electrons and the electric dipole polarizability $\\alpha_d$ for $^{223}$Rn. Our relativistic random-phase approximation (RPA) results are substantially larger than those of lower-order relativistic many-body perturbation theory (MBPT) and the results based on the relativistic coupled-cluster (RCC) method with single and double excitations (CCSD) are the most accurate to date for all the three properties that we have considered. We obtain $d_A = 4.85(6) \\times 10^{-20} C_T \\ |e| \\ cm$ from T-PT interaction, $d_A=2.89(4) \\times 10^{-17} {S/(|e|\\ fm^3)}$ from NSM interaction and $\\alpha_d=35.27(9) \\ ea_0^3$. The former two results in combination with the measured value of $^{223}$Rn EDM, when it becomes available, could yield the best limits for the T-...

Sahoo, B K; Das, B P

2014-01-01

324

NASA Astrophysics Data System (ADS)

An accurate description of electronic excitations is essential to model and understand the properties of several materials of fundamental and technological interest. First principles, many-body techniques based on Green's functions are promising approaches that can provide an accurate description of excited state properties; however their applicability has long been hindered by their numerical complexity. In this talk we will summarize some recent methodological developments based on many-body perturbation theory for the efficient calculation of optical absorption spectra [1], photoemission spectra [2], and multiple exciton generation rates [3]. Several applications to realistic materials will be presented, with emphasis on materials for solar energy applications; these include silicon nanowires and bulk tungsten oxide, that are promising photoelectrode materials in water splitting solar cells, molecules used in organic photovoltaics, and semiconductor nanoparticles with potential use in third generation photovoltaic cells based on multiple exciton generation. Work done in collaboration with Y. Ping, T. A. Pham, M. Voros, D. Lu, H.-V. Nguyen, S. Wippermann, A. Gali, G. T. Zimanyi, and G. Galli.[4pt] ^*Present address[4pt] [1] D. Rocca, D. Lu,G. Galli, J. Chem. Phys. 133, 164109 (2010); D. Rocca, Y. Ping, R. Gebauer, G. Galli, Phys. Rev. B 85, 045116 (2012).[0pt] [2] H.-V. Nguyen, T.A. Pham, D. Rocca, G. Galli, Phys. Rev. B 85, 081101 (2012).[0pt] [3] M. Voros, D. Rocca, G. Galli, G.T. Zimanyi, A. Gali, submitted (2012).

Rocca, Dario

2013-03-01

325

Quantum Harmonic Oscillator Systems with Disorder

NASA Astrophysics Data System (ADS)

We study many-body properties of quantum harmonic oscillator lattices with disorder. A sufficient condition for dynamical localization, expressed as a zero-velocity Lieb-Robinson bound, is formulated in terms of the decay of the eigenfunction correlators for an effective one-particle Hamiltonian. We show how state-of-the-art techniques for proving Anderson localization can be used to prove that these properties hold in a number of standard models. We also derive bounds on the static and dynamic correlation functions at both zero and positive temperature in terms of one-particle eigenfunction correlators. In particular, we show that static correlations decay exponentially fast if the corresponding effective one-particle Hamiltonian exhibits localization at low energies, regardless of whether there is a gap in the spectrum above the ground state or not. Our results apply to finite as well as to infinite oscillator systems. The eigenfunction correlators that appear are more general than those previously studied in the literature. In particular, we must allow for functions of the Hamiltonian that have a singularity at the bottom of the spectrum. We prove exponential bounds for such correlators for some of the standard models.

Nachtergaele, Bruno; Sims, Robert; Stolz, Günter

2012-12-01

326

Determinism Beneath Composite Quantum Systems

NASA Astrophysics Data System (ADS)

This paper aims at the development of 't Hooft's quantization proposal to describe composite quantum mechanical systems. In particular, we show how 't Hooft's method can be utilized to obtain from two classical Bateman oscillators a composite quantum system corresponding to a quantum isotonic oscillator. For a suitable range of parameters, the composite system can be also interpreted as a particle in an effective magnetic field interacting through a spin-orbital interaction term. In the limit of a large separation from the interaction region we can identify the irreducible subsystems with two independent quantum oscillators.

Blasone, Massimo; Vitiello, Giuseppe; Jizba, Petr; Scardigli, Fabio

327

Set Stabilizability of Quantum Systems

We explore set-stabilizability by constrained controls, and both controllability and stabilizability can be regarded as the special case of set-stabilizability. We not only clarify how to define an equilibrium point of Schr$\\ddot{o}$dinger Equations, but also establish the necessary and sufficient conditions for stabilizability of quantum systems. Unfortunately, it is revealed that the necessary conditions are quite strict for stabilizability of some concrete quantum systems like nuclear spin systems, and this further justifies the introduction of set-stabilizability notion. It is also exemplified that set-stabilizability can be used for investigating quantum information processing problems including quantum information storage and entangled states generation.

Ming Zhang; Zairong Xi; Tzyh-Jong Tarn

2014-01-20

328

We investigate the role of quantum mechanical effects in the central stability concept of evolutionary game theory, i.e., an evolutionarily stable strategy (ESS). Using two and three-player symmetric quantum games we show how the presence of quantum phenomenon of entanglement can be crucial to decide the course of evolutionary dynamics in a population of interacting individuals.

A. Iqbal; A. H. Toor

2002-01-01

329

Controlling Atomic, Solid-State and Hybrid Systems for Quantum Information Processing

NASA Astrophysics Data System (ADS)

Quantum information science involves the use of precise control over quantum systems to explore new technologies. However, as quantum systems are scaled up they require an ever deeper understanding of many-body physics to achieve the required degree of control. Current experiments are entering a regime which requires active control of a mesoscopic number of coupled quantum systems or quantum bits (qubits). This thesis describes several approaches to this goal and shows how mesoscopic quantum systems can be controlled and utilized for quantum information tasks. The first system we consider is the nuclear spin environment of GaAs double quantum dots containing two electrons. We show that the through appropriate control of dynamic nuclear polarization one can prepare the nuclear spin environment in three distinct collective quantum states which are useful for quantum information processing with electron spin qubits. We then investigate a hybrid system in which an optical lattice is formed in the near field scattering off an array of metallic nanoparticles by utilizing the plasmonic resonance of the nanoparticles. We show that such a system would realize new regimes of dense, ultra-cold quantum matter and can be used to create a quantum network of atoms and plasmons. Finally we investigate quantum nonlinear optical systems. We show that the intrinsic nonlinearity for plasmons in graphene can be large enough to make a quantum gate for single photons. We also consider two nonlinear optical systems based on ultracold gases of atoms. In one case, we demonstrate an all-optical single photon switch using cavity quantum electrodynamics (QED) and slow light. In the second case, we study few photon physics in strongly interacting Rydberg polariton systems, where we demonstrate the existence of two and three photon bound states and study their properties.

Gullans, Michael John

330

NASA Astrophysics Data System (ADS)

Many-body electron-electron interaction effects are theoretically considered in monolayer graphene from a continuum effective field-theoretic perspective by going beyond the standard leading-order single-loop perturbative renormalization group (RG) analysis. Given that the effective (bare) coupling constant (i.e., the fine structure constant) in graphene is of order unity, which is neither small to justify a perturbative expansion nor large enough for strong-coupling theories to be applicable, the problem is a difficult one, with some similarity to (2+1)-dimensional strong-coupling quantum electrodynamics (QED). In this work, we take a systematic and comprehensive analytical approach in theoretically studying graphene many-body effects, primarily at the Dirac point (i.e., in undoped, intrinsic graphene), by going up to three loops in the diagrammatic expansion to both ascertain the validity of a perturbative expansion in the coupling constant and to develop a RG theory that can be used to estimate the actual quantitative renormalization effect to higher-order accuracy. Electron-electron interactions are expected to play an important role in intrinsic graphene due to the absence of screening at the Dirac (charge neutrality) point, potentially leading to strong deviations from the Fermi-liquid description around the charge neutrality point where the graphene Fermi velocity should manifest an ultraviolet logarithmic divergence because of the linear band dispersion. While no direct signatures for non-Fermi-liquid behavior at the Dirac point have yet been observed experimentally, there is ample evidence for the interaction-induced renormalization of the graphene velocity as the Dirac point is approached by lowering the carrier density. We provide a critical comparison between theory and experiment, using both higher-order diagrammatic and random phase approximation (i.e., infinite-order bubble diagrams) calculations, emphasizing future directions for a deeper understanding of the graphene effective field theory. We find that while the one-loop RG analysis gives reasonable quantitative agreement with the experimental data, both for graphene in vacuum and graphene on substrates, particularly when dynamical screening effects and finite carrier density effects are incorporated in the theory through the random phase approximation, the two-loop analysis reveals an interacting strong-coupling critical point in graphene suspended in vacuum signifying either a quantum phase transition or a breakdown of the weak-coupling renormalization group approach. By adapting a version of Dyson's argument for the breakdown of the QED perturbative expansion to the case of graphene, we show that in contrast to QED where the asymptotic perturbative series in the coupling constant converges to at least 137 orders (and possibly to much higher order) before diverging in higher orders, the graphene perturbative series in the coupling constant may manifest asymptotic divergence already in the first or second order in the coupling constant, favoring the conclusion that perturbation theory may be inadequate, particularly for graphene suspended in vacuum. We propose future experiments and theoretical directions to make further progress on this important and difficult problem. The question of convergence of the asymptotic perturbative expansion for graphene many-body effects is discussed critically in the context of the available experimental results and our theoretical calculations.

Barnes, Edwin; Hwang, E. H.; Throckmorton, R. E.; Das Sarma, S.

2014-06-01

331

Quantum Effects in Biological Systems

NASA Astrophysics Data System (ADS)

The debates about the trivial and non-trivial effects in biological systems have drawn much attention during the last decade or so. What might these non-trivial sorts of quantum effects be? There is no consensus so far among the physicists and biologists regarding the meaning of "non-trivial quantum effects". However, there is no doubt about the implications of the challenging research into quantum effects relevant to biology such as coherent excitations of biomolecules and photosynthesis, quantum tunneling of protons, van der Waals forces, ultrafast dynamics through conical intersections, and phonon-assisted electron tunneling as the basis for our sense of smell, environment assisted transport of ions and entanglement in ion channels, role of quantum vacuum in consciousness. Several authors have discussed the non-trivial quantum effects and classified them into four broad categories: (a) Quantum life principle; (b) Quantum computing in the brain; (c) Quantum computing in genetics; and (d) Quantum consciousness. First, I will review the above developments. I will then discuss in detail the ion transport in the ion channel and the relevance of quantum theory in brain function. The ion transport in the ion channel plays a key role in information processing by the brain.

Roy, Sisir

2014-07-01

332

Many-body GW calculation of the oxygen vacancy in ZnO

Density-functional theory (DFT) calculations of defect levels in semiconductors based on approximate functionals are subject to considerable uncertainties, in particular due to inaccurate band-gap energies. Testing previous correction methods by many-body GW calculations for the O vacancy in ZnO, we find that: (i) The GW quasiparticle shifts of the V{sub O} defect states increase the spitting between occupied and unoccupied states due to self-interaction correction, and do not reflect the conduction- versus valence-band character. (ii) The GW quasiparticle energies of charged defect states require important corrections for supercell finite-size effects. (iii) The GW results are robust with respect to the choice of the underlying DFT or hybrid-DFT functional, and the (2+/0) donor transition lies below midgap, close to our previous prediction employing rigid band-edge shifts.

Lany, Stephan; Zunger, Alex

2010-01-01

333

A many-body problem with point interactions on two-dimensional manifolds

NASA Astrophysics Data System (ADS)

A non-perturbative renormalization of a many-body problem, where non-relativistic bosons living on a two-dimensional Riemannian manifold interact with each other via the two-body Dirac delta potential, is given by the help of the heat kernel defined on the manifold. After this renormalization procedure, the resolvent becomes a well-defined operator expressed in terms of an operator (called principal operator) which includes all the information about the spectrum. Then, the ground state energy is found in the mean-field approximation and we prove that it grows exponentially with the number of bosons. The renormalization group equation (or Callan-Symanzik equation) for the principal operator of the model is derived and the ? function is exactly calculated for the general case, which includes all particle numbers.

Erman, Fatih; Teoman Turgut, O.

2013-02-01

334

Simulations of prompt many-body ionization in a frozen Rydberg gas

NASA Astrophysics Data System (ADS)

The results of a theoretical investigation of prompt many-body ionization are reported. Our calculations address an experiment that reported ionization in Rydberg gases for densities two orders of magnitude less than expected from ionization between pairs of atoms. The authors argued that the results were due to the simultaneous interaction between many atoms. We performed classical calculations for many interacting Rydberg atoms with the ions fixed in space and have found that the many-atom interaction does allow ionization at lower densities than estimates from two-atom interactions. However, we found that the density fluctuations in a gas play a larger role. These two effects are an order of magnitude too small to account for the experimental results suggesting at least one other mechanism strongly affects ionization.

Robicheaux, F.; Goforth, M. M.; Phillips, M. A.

2014-08-01

335

NASA Astrophysics Data System (ADS)

A stochastic algorithm is proposed that can compute the basis-set-incompleteness correction to the second-order many-body perturbation (MP2) energy of a polyatomic molecule. It evaluates the sum of two-, three-, and four-electron integrals over an explicit function of electron-electron distances by a Monte Carlo (MC) integration at an operation cost per MC step increasing only quadratically with size. The method can reproduce the corrections to the MP2/cc-pVTZ energies of H2O, CH4, and C6H6 within a few mEh after several million MC steps. It circumvents the resolution-of-the-identity approximation to the nonfactorable three-electron integrals usually necessary in the conventional explicitly correlated (R12 or F12) methods.

Willow, Soohaeng Yoo; Zhang, Jinmei; Valeev, Edward F.; Hirata, So

2014-01-01

336

Ab Initio Many-Body Calculations Of Nucleon-Nucleus Scattering

We develop a new ab initio many-body approach capable of describing simultaneously both bound and scattering states in light nuclei, by combining the resonating-group method with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters. This approach preserves translational symmetry and Pauli principle. We outline technical details and present phase shift results for neutron scattering on {sup 3}H, {sup 4}He and {sup 10}Be and proton scattering on {sup 3,4}He, using realistic nucleon-nucleon (NN) potentials. Our A = 4 scattering results are compared to earlier ab initio calculations. We find that the CD-Bonn NN potential in particular provides an excellent description of nucleon-{sup 4}He S-wave phase shifts. We demonstrate that a proper treatment of the coupling to the n-{sup 10}Be continuum is successful in explaining the parity-inverted ground state in {sup 11}Be.

Quaglioni, S; Navratil, P

2008-12-17

337

Charge-Transfer Excited States in Aqueous DNA: Insights from Many-Body Green's Function Theory

NASA Astrophysics Data System (ADS)

Charge-transfer (CT) excited states play an important role in the excited-state dynamics of DNA in aqueous solution. However, there is still much controversy on their energies. By ab initio many-body Green's function theory, together with classical molecular dynamics simulations, we confirm the existence of CT states at the lower energy side of the optical absorption maximum in aqueous DNA as observed in experiments. We find that the hydration shell can exert strong effects (˜1 eV) on both the electronic structure and CT states of DNA molecules through dipole electric fields. In this case, the solvent cannot be simply regarded as a macroscopic screening medium as usual. The influence of base stacking and base pairing on the CT states is also discussed.

Yin, Huabing; Ma, Yuchen; Mu, Jinglin; Liu, Chengbu; Rohlfing, Michael

2014-06-01

338

The ionization potential of aqueous hydroxide computed using many-body perturbation theory

NASA Astrophysics Data System (ADS)

The ionization potentials of electrolyte solutions provide important information about the electronic structure of liquids and solute-solvent interactions. We analyzed the positions of solute and solvent bands of aqueous hydroxide and the influence of the solvent environment on the ionization potential of hydroxide ions. We used the concept of a computational hydrogen electrode to define absolute band positions with respect to vacuum. We found that many-body perturbation theory in the G0 W0 approximation substantially improves the relative and absolute positions of the band edges of solute and solvent with respect to those obtained within Density Functional Theory, using semi-local functionals, yielding results in satisfactory agreement with recent experiments.

Opalka, Daniel; Pham, Tuan Anh; Sprik, Michiel; Galli, Giulia

2014-07-01

339

Probing the electronic structure of liquid water with many-body perturbation theory

NASA Astrophysics Data System (ADS)

We present a first-principles investigation of the electronic structure of liquid water based on many-body perturbation theory (MBPT), within the G0W0 approximation. The liquid quasiparticle band gap and the position of its valence band maximum and conduction band minimum with respect to vacuum were computed and it is shown that the use of MBPT is crucial to obtain results that are in good agreement with experiment. We found that the level of theory chosen to generate molecular dynamics trajectories may substantially affect the electronic structure of the liquid, in particular, the relative position of its band edges and redox potentials. Our results represent an essential step in establishing a predictive framework for computing the relative position of water redox potentials and the band edges of semiconductors and insulators.

Pham, T. Anh; Zhang, Cui; Schwegler, Eric; Galli, Giulia

2014-02-01

340

Further improvement in the variational many-body wave functions for light nuclei

NASA Astrophysics Data System (ADS)

An improved variational ansatz is proposed and implemented for variational many-body wave functions for light nuclei with nucleons interacting through Argonne (AV18) and Urbana IX (UIX) three-nucleon interactions. The new ansatz is based upon variationally distinguishing between the various components of the two-body Jastrow and operatorial correlations, which are operated upon by three-body and spin-orbit correlations. We obtain noticeable improvement in the quality of the wave function and lowering of the energies compared to earlier results. The new energies are -8.38(1), -28.07(1), and -29.90(1) MeV for 3H, 4He, and 6Li, respectively. Though, the present improved ansatz still fails to stabilize the 6Li nucleus against a breakup into an ? particle and a deuteron by 390 KeV; nonetheless, it is an improvement over previous studies.

Usmani, Q. N.; Anwar, K.; Abdullah, Nooraihan

2012-09-01

341

Many-body treatment of white dwarf and neutron stars on the brane

Brane-world models suggest modification of Newton's law of gravity on the 3-brane at submillimeter scales. The brane-world induced corrections are in higher powers of inverse distance and appear as additional terms with the Newtonian potential. The average interparticle distance in white dwarf and neutron stars is 10{sup -10} cms and 10{sup -13} cms, respectively, and therefore, the effect of submillimeter corrections needs to be investigated. We show, by carrying out simple many-body calculations, that the mass and mass-radius relationship of the white dwarf and neutron stars are not effected by submillimeter corrections. However, our analysis shows that the correction terms in the effective theory give rise to force akin to surface tension in normal liquids.

Azam, Mofazzal [Theoretical Physics Division, Bhabha Atomic Research Centre, Mumbai (India); Sami, M. [Inter-University Centre for Astronomy and Astrophysics, Pune (India)

2005-07-15

342

We apply the quasiparticle self-consistent GW approximation (QSGW) to some of the iron pnictide and chalcogenide superconductors. We compute Fermi surfaces and density of states, and find excellent agreement with experiment, substantially improving over standard band-structure methods. Analyzing the QSGW self-energy we discuss nonlocal and dynamic contributions to effective masses. We present evidence that the two contributions are mostly separable, since the quasiparticle weight is found to be essentially independent of momentum. The main effect of nonlocality is captured by the static but nonlocal QSGW effective potential. Moreover, these nonlocal self-energy corrections, absent in, e.g., dynamical mean field theory, can be relatively large. We show, on the other hand, that QSGW only partially accounts for dynamic renormalizations at low energies. These findings suggest that QSGW combined with dynamical mean field theory will capture most of the many-body physics in the iron pnictides and chalcogenides. PMID:23368252

Tomczak, Jan M; van Schilfgaarde, M; Kotliar, G

2012-12-01

343

Quantum Computing via The Bethe Ansatz

We recognize quantum circuit model of computation as factorisable scattering model and propose that a quantum computer is associated with a quantum many-body system solved by the Bethe ansatz. As an typical example to support our perspectives on quantum computation, we study quantum computing in one-dimensional nonrelativistic system with delta-function interaction, where the two-body scattering matrix satisfies the factorisation equation (the quantum Yang--Baxter equation) and acts as a parametric two-body quantum gate. We conclude by comparing quantum computing via the factorisable scattering with topological quantum computing.

Yong Zhang

2011-06-20

344

The hydrogen bond has been studied by chemists for nearly a century. Interest in this ubiquitous bond has led to several prototypical systems emerging to studying its behavior. Hydrogen chloride clusters stand as one such example. We present here a new many-body potential energy surface for (HCl)n constructed from one-, two-, and three-body interactions. The surface is constructed from previous highly accurate, semiempirical monomer and dimer surfaces, and a new high-level ab initio permutationally invariant full-dimensional three-body potential. The new three-body potential is based on fitting roughly 52,000 three-body energies computed using coupled cluster with single, doubles, perturbative triples, and explicit correlation and the augmented correlation consistent double-? basis set. The first application, described here, is to the ring HCl trimer, for which the many-body representation is exact. The new potential describes all known stationary points of the trimer as well its dissociation to either three monomers or a monomer and a dimer. The anharmonic vibrational energies are computed for the three H-Cl stretches, using explicit three-mode coupling calculations and local-monomer calculations with Hückel-type coupling. Both methods produce frequencies within 5 cm(-1) of experiment. A wavepacket calculation based on the Hückel model and full-dimensional classical calculation are performed to study the monomer H-Cl stretch vibration-vibration transfer process in the ring HCl trimer. Somewhat surprisingly, the results of the quantum and classical calculations are virtually identical, both exhibiting coherent beating of the excitation between the three monomers. Finally, this representation of the potential is used to study properties of larger clusters, namely to compute optimized geometries of the tetramer, pentamer, and hexamer and to perform explicit four-mode coupling calculations of the tetramer's anharmonic stretch frequencies. The optimized geometries are found to be in agreement with those of previous ab initio studies and the tetramer's anharmonic frequencies are computed within 11 cm(-1) of experiment. PMID:24444294

Mancini, John S; Bowman, Joel M

2014-09-01

345

Many-body electron-electron interaction effects are theoretically considered in monolayer graphene from a continuum effective field-theoretic perspective by going beyond the standard leading-order perturbative renormalization group (RG) analysis. Given that the bare fine structure constant in graphene is of order unity, which is neither small to justify a perturbative expansion nor large enough for strong-coupling theories to be applicable, the problem is a difficult one, with some similarity to 2+1-dimensional strong-coupling quantum electrodynamics (QED). In this work, we take a systematic and comprehensive analytical approach, working primarily at the Dirac point (intrinsic graphene), by going up to three loops in the diagrammatic expansion to both ascertain the validity of perturbation theory and to estimate quantitatively higher-order renormalization effects. While no direct signatures for non-Fermi liquid behavior at the Dirac point have yet been observed experimentally, there is ample evidence for the interaction-induced renormalization of the graphene velocity as the carrier density approaches zero. We provide a critical comparison between theory and experiment, using both bare- and screened-interaction (RPA) calculations. We find that while the one-loop RG analysis gives reasonable agreement with the experimental data, especially when screening and finite-density effects are included through the RPA, the two-loop analysis reveals a strong-coupling critical point in suspended graphene, signifying either a quantum phase transition or a breakdown of the weak-coupling RG approach. We show that the latter is more likely by adapting Dyson's argument for the breakdown of perturbative QED to the case of graphene. We propose future experiments and theoretical directions to make further progress on this important and difficult problem.

Edwin Barnes; E. H. Hwang; R. E. Throckmorton; S. Das Sarma

2014-01-27

346

The solvation of the Na(+) ion in helium clusters has been studied theoretically using optimization methods. A many-body empirical potential was developed to account for Na(+)-He and polarization interactions, and the most stable structures of Na(+)Hen clusters were determined using the basin-hopping method. Vibrational delocalization was accounted for using zero-point energy corrections at the harmonic or anharmonic levels, the latter being evaluated from quantum Monte Carlo simulations for spinless particles. From the static perspective, many-body effects are found to play a minor role, and the structures obtained reflect homogeneous covering up to n = 10, followed by polyicosahedral packing above this size, the cluster obtained at n = 12 appearing particularly stable. The cationic impurity binds the closest helium atoms sufficiently to negate vibrational delocalization at small sizes. However, this snowball effect is obliterated earlier than shell completion, the nuclear wavefunctions of (4)HenNa(+) with n = 5-7, and n?>?10 already exhibiting multiple inherent structures. The decrease in the snowball size due to many-body effects is consistent with recent mass spectrometry measurements. PMID:25381523

Issaoui, Noureddine; Abdessalem, Kawther; Ghalla, Houcine; Yaghmour, Saud Jamil; Calvo, Florent; Oujia, Brahim

2014-11-01

347

Decoherence in infinite quantum systems

We review and discuss a notion of decoherence formulated in the algebraic framework of quantum physics. Besides presenting some sufficient conditions for the appearance of decoherence in the case of Markovian time evolutions we provide an overview over possible decoherence scenarios. The framework for decoherence we establish is sufficiently general to accommodate quantum systems with infinitely many degrees of freedom.

Blanchard, Philippe; Hellmich, Mario [Faculty of Physics, University of Bielefeld, Universitaetsstr. 25, 33615 Bielefeld (Germany); Bundesamt fuer Strahlenschutz (Federal Office for Radiation Protection), Willy-Brandt-Strasse 5, 38226 Salzgitter (Germany)

2012-09-01

348

Classical equations for quantum systems

The origin of the phenomenological deterministic laws that approximately govern the quasiclassical domain of familiar experience is considered in the context of the quantum mechanics of closed systems such as the universe as a whole. A formulation of quantum mechanics is used that predicts probabilities for the individual members of a set of alternative coarse-grained histories that decohere, which means

Murray Gell-Mann; James B. Hartle

1993-01-01

349

Energy density matrix formalism for interacting quantum systems: a quantum Monte Carlo study

We develop an energy density matrix that parallels the one-body reduced density matrix (1RDM) for many-body quantum systems. Just as the density matrix gives access to the number density and occupation numbers, the energy density matrix yields the energy density and orbital occupation energies. The eigenvectors of the matrix provide a natural orbital partitioning of the energy density while the eigenvalues comprise a single particle energy spectrum obeying a total energy sum rule. For mean-field systems the energy density matrix recovers the exact spectrum. When correlation becomes important, the occupation energies resemble quasiparticle energies in some respects. We explore the occupation energy spectrum for the finite 3D homogeneous electron gas in the metallic regime and an isolated oxygen atom with ground state quantum Monte Carlo techniques imple- mented in the QMCPACK simulation code. The occupation energy spectrum for the homogeneous electron gas can be described by an effective mass below the Fermi level. Above the Fermi level evanescent behavior in the occupation energies is observed in similar fashion to the occupation numbers of the 1RDM. A direct comparison with total energy differences demonstrates a quantita- tive connection between the occupation energies and electron addition and removal energies for the electron gas. For the oxygen atom, the association between the ground state occupation energies and particle addition and removal energies becomes only qualitative. The energy density matrix provides a new avenue for describing energetics with quantum Monte Carlo methods which have traditionally been limited to total energies.

Krogel, Jaron T [ORNL] [ORNL; Kim, Jeongnim [ORNL] [ORNL; Reboredo, Fernando A [ORNL] [ORNL

2014-01-01

350

Energy density matrix formalism for interacting quantum systems: Quantum Monte Carlo study

NASA Astrophysics Data System (ADS)

We develop an energy density matrix that parallels the one-body reduced density matrix (1RDM) for many-body quantum systems. Just as the density matrix gives access to the number density and occupation numbers, the energy density matrix yields the energy density and orbital occupation energies. The eigenvectors of the matrix provide a natural orbital partitioning of the energy density while the eigenvalues comprise a single-particle energy spectrum obeying a total energy sum rule. For mean-field systems the energy density matrix recovers the exact spectrum. When correlation becomes important, the occupation energies resemble quasiparticle energies in some respects. We explore the occupation energy spectrum for the finite 3D homogeneous electron gas in the metallic regime and an isolated oxygen atom with ground-state quantum Monte Carlo techniques implemented in the qmcpack simulation code. The occupation energy spectrum for the homogeneous electron gas can be described by an effective mass below the Fermi level. Above the Fermi level evanescent behavior in the occupation energies is observed in similar fashion to the occupation numbers of the 1RDM. A direct comparison with total energy differences shows a quantitative connection between the occupation energies and electron addition and removal energies for the electron gas. For the oxygen atom, the association between the ground-state occupation energies and particle addition and removal energies becomes only qualitative. The energy density matrix provides an avenue for describing energetics with quantum Monte Carlo methods which have traditionally been limited to total energies.

Krogel, Jaron T.; Kim, Jeongnim; Reboredo, Fernando A.

2014-07-01

351

Landau-Zener transitions in noisy environment and many-body systems

temperature our theory gives a beautiful result which coincides with that of other authors. Our initial attempts to solve two experimental puzzles - an isotope effect and the quantized hysteresis curve of a single molecular magnet - are also discussed...

Sun, Deqiang

2010-01-16

352

Many-body effects in the normal-state polaron system

NASA Astrophysics Data System (ADS)

Dielectric response function of small polarons (SP's) is studied. The Debye radius is small, which reduces a short-range Coulomb repulsion to the magnitude of the order of the small-polaron (SP) bandwidth. Polaron-polaron attraction is enhanced by screening. A critical temperature of the bipolaron formation is found. The dielectric response becomes dynamic in a very low-frequency region. A multiphonon diagram technique is developed to obtain vibration excitations, that are a mixture of phonons with polaronic plasmons. A microscopic model of the anomalous extra modes, observed in neutron-scattering experiments in La2CuO4, is proposed.

Alexandrov, A. S.

1992-08-01

353

Collective many-body van der Waals interactions in molecular systems

proper- ties. Cases studied include the binding affinity of ellipticine, a DNA- intercalating anticancer agent, the relative energetics between the A- and B-conformations of DNA, and the thermodynamic for in molecular simulations. intermolecular interactions dispersion interactions force fields DNA stability

354

Derivation of the nonlinear Schrodinger equation from a many body Coulomb system

We consider the time evolution of N bosonic particles interacting via a mean field Coulomb potential. Suppose the initial state is a product wavefunction. We show that at any finite time the correlation functions factorize in the limit N ? ?. Furthermore, the limiting one particle density matrix satisfies the nonlinear Hartree equation. The key ingredients are the uniqueness of

Laszlo Erdýos

355

Path integrals and degrees of freedom in many-body systems and relativistic field theories

The identification of physical degrees of freedom is sometimes obscured in the path integral formalism, and this makes it difficult to impose some constraints or to do some approximations. I review a number of cases where the difficulty is overcame by deriving the path integral from the operator form of the partition function after such identification has been made.

F. Palumbo

2004-12-07

356

Open Quantum Systems and Quantum Algorithms

The model of open quantum systems is adopted to describe the non-local dynamical behaviour of qubits processed by entangling gates. The analysis gets to the conclusion that a distinction between evaluation steps and task-oriented computing steps is justified only within classical computation. In fact, the use of entangling gates permits to reduce two steps (evaluation and calculation) to a single computational one, and this determines an effective computational speed-up. The application of the open quantum systems model suggests that the reduction to one-computational step is strongly related to the existence of Universal Dynamical Maps describing the evolution of component systems of two-qubits gates. As the description in terms of Universal Dynamical Map is possible only in the presence of a separable initial state, it turns out that the internal reduced dynamics with respect to entangling gates is neither unitary nor Markovian. The fact imposes a holistic vision on the structure of the algorithm, where the entangling gates shall remain indivisible unities, or black boxes, in order to preserve computational speed as well as reversibility. This fact suggests to adopt a perspective on computation which is completely non-classical: the whole algorithm turns out not to be the sequence of its temporal parts.

Stefano Bonzio; Paola Verrucchi

2013-01-09

357

Controlling the gap of fullerene microcrystals by applying pressure: Role of many-body effects

We characterize the optical properties of C_60 fullerene microcrystals as a function of hydrostatic pressure. Calculations were done using first-principles many-body theories based on evaluating electronic energy levels in the GW approximation. We compute electronic excited states in the crystal by diagonalizing the Bethe-Salpeter equation (BSE). Our results confirm the existence of bound excitons in the crystal. Both the electronic gap and optical gap decrease continuously and non-linearly as pressure of up to 6 GPa is applied. As a result, the absorption spectrum shows strong redshift. We also observe that "negative" pressure shows the opposite behavior: the gaps increase and the optical spectrum shifts toward the blue end of the spectrum. Negative pressure can be realized by adding cubane (C_8H_8) or other molecules with similar size to the interstitials of the microcrystal. For the moderate lattice distortions studied here, we have found that the optical properties of fullerene microcrystals with intercalated cubane are similar to the ones of an expanded undoped microcrystal. Based on these findings, we propose doped C_60 as active element in piezo-optical devices.

Tiago, Murilo L [ORNL; Reboredo, Fernando A [ORNL

2009-01-01

358

Thermal conductivity and energetic recoils in UO2 using a many-body potential model.

Classical molecular dynamics simulations have been performed on uranium dioxide (UO2) employing a recently developed many-body potential model. Thermal conductivities are computed for a defect free UO2 lattice and a radiation-damaged, defect containing lattice at 300 K, 1000 K and 1500 K. Defects significantly degrade the thermal conductivity of UO2 as does the presence of amorphous UO2, which has a largely temperature independent thermal conductivity of ?1.4 Wm(-1) K(-1). The model yields a pre-melting superionic transition temperature at 2600 K, very close to the experimental value and the mechanical melting temperature of 3600 K, slightly lower than those generated with other empirical potentials. The average threshold displacement energy was calculated to be 37 eV. Although the spatial extent of a 1 keV U cascade is very similar to those generated with other empirical potentials and the number of Frenkel pairs generated is close to that from the Basak potential, the vacancy and interstitial cluster distribution is different. PMID:25398161

Qin, M J; Cooper, M W D; Kuo, E Y; Rushton, M J D; Grimes, R W; Lumpkin, G R; Middleburgh, S C

2014-12-10

359

Many-body dissipative particle dynamics simulation of liquid/vapor and liquid/solid interactions

The combination of short-range repulsive and long-range attractive forces in Many-body Dissipative Particle Dynamics (MDPD) is examined at a vapor/liquid and liquid/solid interface. Based on the radial distribution of the virial pressure in a drop at equilibrium, a systematic study is carried out to characterize the sensitivity of the surface tension coefficient with respect to the inter-particle interaction parameters. For the first time, this study highlights the approximately cubic dependence of the surface tension coefficient on the bulk density of the fluid. In capillary flow, MDPD solutions are shown to satisfy the condition on the wavelength of an axial disturbance leading to the pinch-off of a cylindrical liquid thread. Correctly, no pinch-off occurs below the cutoff wavelength. MDPD is augmented by a set of bell-shaped weight functions to model interaction with a solid wall. There, hydrophilic and hydrophobic behaviors, including the occurrence of slip in the latter, are reproduced using a modification in the weight function that avoids particle clustering. Finally, the dynamics of droplets entering an inverted Y-shaped fracture junction is correctly captured in simulations parameterized by the Bond number, proving the flexibility of MDPD in modeling interface-dominated flows.

Arienti, Marco; Pan, Wenxiao; Li, Xiaoyi; Karniadakis, George E.

2011-05-27

360

Quantum Noise as an Entanglement Meter

, phase transitions, quantum information, numerical studies of strongly correlated systems Wilczek correlations between two parts of a many-body system Useful in: field theory, black holes, quantum quenchesXiv: 0804.1377 Part II: Coherent Particle Transfer in an On-Demand Single-Electron Source with Jonathan

Gabrieli, John

361

Preconditioned Quantum Linear System Algorithm

NASA Astrophysics Data System (ADS)

We describe a quantum algorithm that generalizes the quantum linear system algorithm [Harrow et al., Phys. Rev. Lett. 103, 150502 (2009)] to arbitrary problem specifications. We develop a state preparation routine that can initialize generic states, show how simple ancilla measurements can be used to calculate many quantities of interest, and integrate a quantum-compatible preconditioner that greatly expands the number of problems that can achieve exponential speedup over classical linear systems solvers. To demonstrate the algorithm’s applicability, we show how it can be used to compute the electromagnetic scattering cross section of an arbitrary target exponentially faster than the best classical algorithm.

Clader, B. D.; Jacobs, B. C.; Sprouse, C. R.

2013-06-01

362

A hybrid quantum system of ultracold atoms and trapped ions

NASA Astrophysics Data System (ADS)

In the last decades, trapped ions and ultracold atoms have emerged as exceptionally controllable experimental systems to investigate fundamental physics, ranging from quantum information science to simulations of condensed matter models. Even though they share some common grounds in experimental techniques, such as laser cooling, ion trapping and atom trapping have developed very much independently, and only little cross-pollination has been seen. In our experiment we study how cold atoms can be combined with single trapped ions to create a new hybrid quantum system with tailored properties. We have deterministically placed a single ion into an atomic Bose Einstein condensate and demonstrated independent control over the two components within the hybrid system. We have studied the fundamental interaction processes and observed sympathetic cooling of the single ion by the condensate. Additionally, we have characterized elastic and inelastic atom- ion collisions and measured the energy-dependent reaction rate constants. Our experiment paves the way for coupling atomic quantum many-body states to an independently controllable single-particle, giving access to a wealth of novel physics and to completely new detection and manipulation techniques.

Sias, Carlo; Ratschbacher, Lothar; Zipkes, Christoph; Koehl, Michael

2011-06-01

363

Pushing the limits of the eigenstate thermalization hypothesis towards mesoscopic quantum systems.

In the ongoing discussion on thermalization in closed quantum many-body systems, the eigenstate thermalization hypothesis has recently been proposed as a universal concept and has attracted considerable attention. So far this concept is, as the name states, hypothetical. The majority of attempts to overcome this hypothetical character are based on exact diagonalization, which implies for, e.g., spin systems a limitation of roughly 15 spins. In this Letter we present an approach that pushes this limit up to system sizes of roughly 35 spins, thereby going significantly beyond what is possible with exact diagonalization. A concrete application to a Heisenberg spin ladder which yields conclusive results is demonstrated. PMID:24745395

Steinigeweg, R; Khodja, A; Niemeyer, H; Gogolin, C; Gemmer, J

2014-04-01

364

Pushing the Limits of the Eigenstate Thermalization Hypothesis towards Mesoscopic Quantum Systems

NASA Astrophysics Data System (ADS)

In the ongoing discussion on thermalization in closed quantum many-body systems, the eigenstate thermalization hypothesis has recently been proposed as a universal concept and has attracted considerable attention. So far this concept is, as the name states, hypothetical. The majority of attempts to overcome this hypothetical character are based on exact diagonalization, which implies for, e.g., spin systems a limitation of roughly 15 spins. In this Letter we present an approach that pushes this limit up to system sizes of roughly 35 spins, thereby going significantly beyond what is possible with exact diagonalization. A concrete application to a Heisenberg spin ladder which yields conclusive results is demonstrated.

Steinigeweg, R.; Khodja, A.; Niemeyer, H.; Gogolin, C.; Gemmer, J.

2014-04-01

365

Quantum proof systems and entanglement theory

Quantum complexity theory is important from the point of view of not only theory of computation but also quantum information theory. In particular, quantum multi-prover interactive proof systems are defined based on ...

Abolfathe Beikidezfuli, Salman

2009-01-01

366

Contextual logic for quantum systems

In this work we build a quantum logic that allows us to refer to physical magnitudes pertaining to different contexts from a fixed one without the contradictions with quantum mechanics expressed in no-go theorems. This logic arises from considering a sheaf over a topological space associated to the Boolean sublattices of the ortholattice of closed subspaces of the Hilbert space of the physical system. Differently to standard quantum logics, the contextual logic maintains a distributive lattice structure and a good definition of implication as a residue of the conjunction.

Graciela Domenech; Hector Freytes

2007-02-02

367

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) is an important research tool extensively applied in materials science. Running MD on a graphics processing unit (GPU) is an attractive new approach for accelerating MD simulations. Currently, GPU implementations of MD usually run in a one-host-process-one-GPU (OHPOG) scheme. This scheme may pose a limitation on the system size that an implementation can handle due to the small device memory relative to the host memory. In this paper, we present a one-host-process-multiple-GPU (OHPMG) implementation of MD with embedded-atom-model or semi-empirical tight-binding many-body potentials. Because more device memory is available in an OHPMG process, the system size that can be handled is increased to a few million or more atoms. In comparison with the serial CPU implementation, in which Newton's third law is applied to improve the computational efficiency, our OHPMG implementation has achieved a 28.9x-86.0x speedup in double precision, depending on the system size, the cut-off ranges and the number of GPUs. The implementation can also handle a group of small simulation boxes in one run by combining the small boxes into a large box. This approach greatly improves the GPU computing efficiency when a large number of MD simulations for small boxes are needed for statistical purposes.

Hou, Qing; Li, Min; Zhou, Yulu; Cui, Jiechao; Cui, Zhenguo; Wang, Jun

2013-09-01

368

NASA Astrophysics Data System (ADS)

A general method for the development of potential-energy hypersurfaces is presented. The method combines a many-body expansion to represent the potential-energy surface with two-layer neural networks (NN) for each M-body term in the summations. The total number of NNs required is significantly reduced by employing a moiety energy approximation. An algorithm is presented that efficiently adjusts all the coupled NN parameters to the database for the surface. Application of the method to four different systems of increasing complexity shows that the fitting accuracy of the method is good to excellent. For some cases, it exceeds that available by other methods currently in literature. The method is illustrated by fitting large databases of ab initio energies for Sin(n =3,4,…,7) clusters obtained from density functional theory calculations and for vinyl bromide (C2H3Br) and all products for dissociation into six open reaction channels (12 if the reverse reactions are counted as separate open channels) that include C-H and C-Br bond scissions, three-center HBr dissociation, and three-center H2 dissociation. The vinyl bromide database comprises the ab initio energies of 71 969 configurations computed at MP4(SDQ) level with a 6-31G(d,p) basis set for the carbon and hydrogen atoms and Huzinaga's (4333/433/4) basis set augmented with split outer s and p orbitals (43321/4321/4) and a polarization f orbital with an exponent of 0.5 for the bromine atom. It is found that an expansion truncated after the three-body terms is sufficient to fit the Si5 system with a mean absolute testing set error of 5.693×10-4 eV. Expansions truncated after the four-body terms for Sin(n =3,4,5) and Sin(n =3,4,…,7) provide fits whose mean absolute testing set errors are 0.0056 and 0.0212 eV, respectively. For vinyl bromide, a many-body expansion truncated after the four-body terms provides fitting accuracy with mean absolute testing set errors that range between 0.0782 and 0.0808 eV. These errors correspond to mean percent errors that fall in the range 0.98%-1.01%. Our best result using the present method truncated after the four-body summation with 16 NNs yields a testing set error that is 20.3% higher than that obtained using a 15-dimensional (15-140-1) NN to fit the vinyl bromide database. This appears to be the price of the added simplicity of the many-body expansion procedure.

Malshe, M.; Narulkar, R.; Raff, L. M.; Hagan, M.; Bukkapatnam, S.; Agrawal, P. M.; Komanduri, R.

2009-05-01

369

Simulation of open quantum systems

We present an approach for the semiclassical treatment of open quantum systems. An expansion into localized states allows restriction of a simulation to a fraction of the environment that is located within a predefined vicinity of the system. Adding and dropping environmental particles during the simulation yields an effective reduction of the size of the system that is being treated.

Florian Mintert; Eric J. Heller

2008-03-27

370

Classical many-body polarizable force fields were developed for n-alkanes, perflouroalkanes, polyethers, ketones, and linear and cyclic carbonates on the basis of quantum chemistry dimer energies of model compounds and empirical thermodynamic liquid-state properties. The dependence of the electron correlation contribution to the dimer binding energy on basis-set size and level of theory was investigated as a function of molecular separation for a number of alkane, ether, and ketone dimers. Molecular dynamics (MD) simulations of the force fields accurately predicted structural, dynamic, and transport properties of liquids and unentangled polymer melts. On average, gas-phase dimer binding energies predicted with the force field were between those from MP2/aug-cc-pvDz and MP2/aug-cc-pvTz quantum chemistry calculations. PMID:16553446

Borodin, Oleg; Smith, Grant D

2006-03-30

371

Band alignment of semiconductors from density-functional theory and many-body perturbation theory

NASA Astrophysics Data System (ADS)

The band lineup, or alignment, of semiconductors is investigated via first-principles calculations based on density functional theory (DFT) and many-body perturbation theory (MBPT). Twenty-one semiconductors including C, Si, and Ge in the diamond structure, BN, AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe in the zinc-blende structure, and GaN and ZnO in the wurtzite structure are considered in view of their fundamental and technological importance. Band alignments are determined using the valence and conduction band offsets from heterointerface calculations, the ionization potential (IP) and electron affinity (EA) from surface calculations, and the valence band maximum and conduction band minimum relative to the branch point energy, or charge neutrality level, from bulk calculations. The performance of various approximations to DFT and MBPT, namely the Perdew-Burke-Ernzerhof (PBE) semilocal functional, the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, and the GW approximation with and without vertex corrections in the screened Coulomb interaction, is assessed using the GW?1 approximation as a reference, where first-order vertex corrections are included in the self-energy. The experimental IPs, EAs, and band offsets are well reproduced by GW?1 for most of the semiconductor surfaces and heterointerfaces considered in this study. The PBE and HSE functionals show sizable errors in the IPs and EAs, in particular for group II-VI semiconductors with wide band gaps, but are much better in the prediction of relative band positions or band offsets due to error cancellation. The performance of the GW approximation is almost on par with GW?1 as far as relative band positions are concerned. The band alignments based on average interfacial band offsets for all pairs of 17 semiconductors and branch point energies agree with explicitly calculated interfacial band offsets with small mean absolute errors of both ˜0.1eV, indicating a good overall transitivity of the band offsets. The alignment based on IPs from selected nonpolar surfaces performs comparably well in the prediction of band offsets at most of the considered interfaces. The maximum errors are, however, as large as 0.3, 0.4, and 0.7 eV for the alignments based on the average band offsets, branch point energies, and IPs, respectively. This margin of error should be taken into account when performing materials screening using these alignments.

Hinuma, Yoyo; Grüneis, Andreas; Kresse, Georg; Oba, Fumiyasu

2014-10-01

372

Second-order many-body perturbation study of solid hydrogen fluoride under pressure.

A linear-scaling, embedded-fragment, second-order many-body perturbation (MP2) method with basis sets up to aug-cc-pVTZ is applied to the antiparallel structure of solid hydrogen fluoride and deuterium fluoride under 0-20 GPa of ambient pressure. The optimized structures, including the lattice parameters and molar volume, and phonon dispersion as well as phonon density of states (DOS), are determined as a function of pressure. The basis-set superposition errors are removed by the counterpoise correction. The structural parameters at 0 GPa calculated by MP2 agree accurately with the observed, making the predicted values at higher pressures a useful pilot for future experiments. The corresponding values obtained by the Hartree-Fock method have large, systematic errors. The MP2/aug-cc-pVDZ frequencies of the infrared- and Raman-active vibrations of the three-dimensional solids are in good agreement with the observed and also justify previous vibrational analyses based on one-dimensional chain models; the non-coincidence of the infrared and Raman mode pairs can be explained as factor-group (Davydov) splitting. The exceptions are one pair of modes in the librational region, for which band assignments based on a one-dimensional chain model need to be revised, as well as the five pseudo-translational modes that exist only in a three-dimensional treatment. The observed pressure dependence of Raman bands in the stretching region, which red-shift with pressure, is accounted for by theory only qualitatively, while that in the pseudo-translational region is reproduced with quantitative accuracy. The present calculation proves to be limited in explaining the complex pressure dependence of the librational modes. The hydrogen-amplitude-weighted phonon DOS at 0 GPa is much less structured than the DOS obtained from one-dimensional models and may be more realistic in view of the also broad, structureless observed inelastic neutron scattering spectra. All major observed peaks can be straightforwardly assigned to the calculated peaks in the DOS. With increasing pressure, MP2 predicts further broadening of bands and breach of the demarcation between the pseudo-translational and librational bands. PMID:22456828

Sode, Olaseni; Hirata, So

2012-06-01

373

Low Energy Quantum System Simulation

A numerical method for solving Schrodinger's equation based upon a Baker-Campbell-Hausdorff (BCH) expansion of the time evolution operator is presented herein. The technique manifestly preserves wavefunction norm, and it can be applied to problems in any number of spatial dimensions. We also identify a particular dimensionless ratio of potential to kinetic energies as a key coupling constant. This coupling establishes characteristic length and time scales for a large class of low energy quantum states, and it guides the choice of step sizes in numerical work. Using the BCH method in conjunction with an imaginary time rotation, we compute low energy eigenstates for several quantum systems coupled to non-trivial background potentials. The approach is subsequently applied to the study of 1D propagating wave packets and 2D bound state time development. Failures of classical expectations uncovered by simulations of these simple systems help develop quantum intuition. Finally, we investigate the response of a Superconducting Quantum Interference Device (SQUID) to a time dependent potential. We discuss how to engineer the potential's energy and time scales so that the SQUID acts as a quantum NOT gate. The notional simulation we present for this gate provides useful insight into the design of one candidate building block for a quantum computer.

Peter Cho; Karl Berggren

2003-10-26

374

Quantum information processing in mesoscopic systems

introduce the Quantum Dots as the solid state system that will primarily be used as the hardware of quantum computation in quantum dots is described. The principal sources of decoherence and the measurementQuantum information processing in mesoscopic systems Jose Luis Garcia Coello A dissertation

Guillas, Serge

375

Applications of Feedback Control in Quantum Systems

We give an introduction to feedback control in quantum systems, as well as an overview of the variety of applications which have been explored to date. This introductory review is aimed primarily at control theorists unfamiliar with quantum mechanics, but should also be useful to quantum physicists interested in applications of feedback control. We explain how feedback in quantum systems

Kurt Jacobs

2006-01-01

376

Hypothesis testing with open quantum systems

Using a quantum circuit model we derive the maximal ability to distinguish which of several candidate Hamiltonians describe an open quantum system. This theory, in particular, provides the maximum information retrievable from continuous quantum measurement records, available when a smaller open quantum system is perturbatively coupled to a broadband quantized environment.

Klaus Molmer

2014-08-20

377

A recently developed relativistic multireference many-body perturbation theory based on multireference configuration-interaction wavefunctions as zeroth-order wavefunctions is outlined. The perturbation theory employs a general class of configuration-interaction wavefunctions as reference functions, and thus is applicable to multiple open valence shell systems with near degeneracy of a manifold of strongly interacting configurations. Multireference many-body perturbation calculations are reported for the ground

Yasuyuki Ishikawa; Juan A. Santana; Elmar Träbert

2010-01-01

378

We study within the many-body Green's function GW and Bethe-Salpeter formalisms the excitation energies of a paradigmatic model dipeptide, focusing on the four lowest-lying local and charge-transfer excitations. Our GW calculations are performed at the self-consistent level, updating first the quasiparticle energies, and further the single-particle wavefunctions within the static Coulomb-hole plus screened-exchange approximation to the GW self-energy operator. Important level crossings, as compared to the starting Kohn-Sham LDA spectrum, are identified. Our final Bethe-Salpeter singlet excitation energies are found to agree, within 0.07 eV, with CASPT2 reference data, except for one charge-transfer state where the discrepancy can be as large as 0.5 eV. Our results agree best with LC-BLYP and CAM-B3LYP calculations with enhanced long-range exchange, with a 0.1 eV mean absolute error. This has been achieved employing a parameter-free formalism applicable to metallic or insulating extended or finite systems. PMID:24320327

Faber, C; Boulanger, P; Duchemin, I; Attaccalite, C; Blase, X

2013-11-21

379

Quantum Entanglement and Quantum Discord in Gaussian Open Systems

In the framework of the theory of open systems based on completely positive quantum dynamical semigroups, we give a description of the continuous-variable quantum entanglement and quantum discord for a system consisting of two noninteracting modes embedded in a thermal environment. Entanglement and discord are used to quantify the quantum correlations of the system. For all values of the temperature of the thermal reservoir, an initial separable Gaussian state remains separable for all times. In the case of an entangled initial Gaussian state, entanglement suppression (entanglement sudden death) takes place for non-zero temperatures of the environment. Only for a zero temperature of the thermal bath the initial entangled state remains entangled for finite times. We analyze the time evolution of the Gaussian quantum discord, which is a measure of all quantum correlations in the bipartite state, including entanglement, and show that quantum discord decays asymptotically in time under the effect of the thermal bath.

Isar, Aurelian [National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, P.O. Box MG-6 (Romania)

2011-10-03

380

Quantum Entanglement in Open Systems

In the framework of the theory of open systems based on completely positive quantum dynamical semigroups, the master equation for two independent harmonic oscillators interacting with an environment is solved in the asymptotic long-time regime. Using the Peres-Simon necessary and sufficient condition for separability of two-mode Gaussian states, we show that the two non-interacting systems become asymptotically entangled for certain environments, so that in the long-time regime they manifest non-local quantum correlations. We calculate also the logarithmic negativity characterizing the degree of entanglement of the asymptotic state.

Isar, Aurelian [Institute of Physics and Nuclear Engineering, Bucharest-Magurele (Romania)

2008-01-24

381

Many-Body Decomposition of the Binding Energies for OH•(H2O)2 and OH•(H2O)3 Complexes

We use ab initio electronic structure methods to calculate the many-body decomposition of the binding energies of the OH?(H2O)n (n=2,3) complexes. We employ MP2 and CCSD(T) levels of theory with aug-cc-pVDZ and aug-cc-pVTZ basis sets and analyze the significance of the non-pairwise interactions between OH radical and the surrounding water molecules. We also evaluate the accuracy of our newly developed potential function, the modified Thole-type model (mTTM), for predicting the many-body terms in these complexes. Our analysis of the many-body contributions to the OH?(H2O)n binding energies clearly shows that they are just as important in the OH interactions with water as they are for interactions in pure water systems. This work was supported by the Division of Chemical Sciences, Office of Basic Energy Sciences of the U.S. Department of Energy (DOE) and was performed in part using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) at the Pacific Northwest National Laboratory. The EMSL is funded by the DOE Office of Biological and Environmental Research. Battelle operates Pacific Northwest National Laboratory for DOE. The authors thank Sotiris Xantheas, Jun Li, Tzvetelin Iordanov, and Jun Cui for helpful discussions and assistance.

Du, Shiyu; Francisco, Joseph S.; Schenter, Gregory K.; Garrett, Bruce C.

2008-02-27

382

Low Energy Quantum System Simulation

A numerical method for solving Schrodinger's equation based upon a Baker-Campbell-Hausdorff (BCH) expansion of the time evolution operator is presented herein. The technique manifestly preserves wavefunction norm, and it can be applied to problems in any number of spatial dimensions. We also identify a particular dimensionless ratio of potential to kinetic energies as a key coupling constant. This coupling establishes characteristic length and time scales for a large class of low energy quantum states, and it guides the choice of step sizes in numerical work. Using the BCH method in conjunction with an imaginary time rotation, we compute low energy eigenstates for several quantum systems coupled to non-trivial background potentials. The approach is subsequently applied to the study of 1D propagating wave packets and 2D bound state time development. Failures of classical expectations uncovered by simulations of these simple systems help develop quantum intuition. Finally, we investigate the response of a Super...

Cho, P; Cho, Peter; Berggren, Karl

2003-01-01

383

Control of the quantum open system via quantum generalized measurement

For any specified pure state of quantum open system, we can construct a kind of quantum generalized measurement (QGM) that the state of the system after measurement will be deterministically collapsed into the specified pure state from any initial state. In other words, any pure state of quantum open system is reachable by QGM. Subsequently, whether the qubit is density matrix controllable is discussed in the case of pure dephasing. Our results reveal that combining QGM with coherent control will enhance the ability of controlling the quantum open system. Furthermore, it is found that the ability to perform QGM on the quantum open system, combined with the ability of coherence control and conditions of decoherence-free subspace, allows us to suppress quantum decoherence.

Zhang Ming; Zhu Xiaocai; Li Xingwei; Hu Dewen [College of Mechatronics and Automation, National University of Defense Technology, Changsha, Hunan 410073 (China); Dai Hongyi [College of Science, National University of Defense Technology, Changsha, Hunan 410073 (China)

2006-03-15

384

Dynamical identification of open quantum systems

I propose a quantum trajectories approach to parametric identification of the effective Hamiltonian for a Markovian open quantum system, and discuss an application motivated by recent experiments in cavity quantum electrodynamics. This example illustrates a strategy for quantum parameter estimation that efficiently utilizes the information carried by correlations between measurements distributed in time.

Hideo Mabuchi

1996-08-13

385

Exploring quantum non-locality with de Broglie-Bohm trajectories.

Here in this paper, it is shown how the quantum nonlocality reshapes probability distributions of quantum trajectories in configuration space. By variationally minimizing the ground state energy of helium atom, we show that there exists an optimal nonlocal quantum correlation length which also minimizes the mean integrated square error of the smooth trajectory ensemble with respect to the exact many-body wave function. The nonlocal quantum correlation length can be used for studies of both static and driven many-body quantum systems. PMID:22280753

Christov, Ivan P

2012-01-21

386

for the interaction of the valence electrons with the core. The configuration-interaction method is then used to find 1996 An ab initio method for high accuracy calculations for atoms with more than one valence electron is described. The effective Hamiltonian for the valence electrons is formed using many-body perturbation theory

Kozlov, Mikhail G

387

Integrals of motion in the Many-Body localized phase SISSA, via Bonomea 265, 34136 Trieste, Italy.

, Italy. INFN, Sezione di Trieste, Strada Costiera 11, 34151 Trieste, Italy. M. Mï¿½ller Abdus Salam ICTP College of the City University of New York, New York, NY 10016 USA on leave from: Abdus Salam ICTP for the many-body localization-delocalization transition. We determine the nature of the processes

MÃ¼ller, Markus

388

Electronic and excitonic properties in the silicon cluster Si[subscript 20] are studied using the many-body Green’s function theory. The implementations of the self-consistencies of both the one-particle Green’s function ...

Zeng, Taofang

389

Many-Body Effects in the Excitation Spectrum of a Defect in SiC Michel Bockstedte,1,2

polytype of silicon carbide (4H-SiC) was extensively investigated and excitation thresholds were assignedMany-Body Effects in the Excitation Spectrum of a Defect in SiC Michel Bockstedte,1,2 Andrea Marini correlations control the photophysics of defects in SiC through both renormal- ization of the quasiparticle

Marini, Andrea

390

Rydberg dressing: understanding of collective many-body effects and implications for experiments

NASA Astrophysics Data System (ADS)

The strong interaction between Rydberg atoms can be used to control the strength and character of the interatomic interaction in ultracold gases by weakly dressing the atoms with a Rydberg state. Elaborate theoretical proposals for the realization of various complex phases and applications in quantum simulation exist. Also a simple model has been already developed that describes the basic idea of Rydberg dressing in a two-atom basis. However, an experimental realization has been elusive so far. We present a model describing the ground state of a Bose-Einstein condensate dressed with a Rydberg level based on the Rydberg blockade. This approach provides an intuitive understanding of the transition from pure two-body interaction to a regime of collective interactions. Furthermore it enables us to calculate the deformation of a three-dimensional sample under realistic experimental conditions in mean-field approximation. We compare full three-dimensional numerical calculations of the ground state to an analytic expression obtained within Thomas-Fermi approximation. Finally we discuss limitations and problems arising in an experimental realization of Rydberg dressing based on our experimental results and point out possible solutions for future approaches. Our work enables the reader to straight forwardly estimate the experimental feasibility of Rydberg dressing in realistic three-dimensional atomic samples.

Balewski, J. B.; Krupp, A. T.; Gaj, A.; Hofferberth, S.; Löw, R.; Pfau, T.

2014-06-01

391

QFS 2010 Satellite Workshop Cold Gases meet Many-Body Theory

fluids, and strongly correlated electron systems. The many sophisticated theoretical methods have been in examining their properties, for both fermionic and bosonic systems. In atomic gases, correlated regimes and fermionic systems on lattices are just a few examples which show clear signatures of correlations

Canet, LÃ©onie

392

A density functional approach to many-body effects in the optical response of atoms

A method for calculating the optical response of finite electronic system which is accurate, computationally simple and lends itself to a ready physical interpretation of the results is presented. A time dependent local density approximation (TDLDA) represents a natural generalization of the usual local density approximation to the ground state properties of a many electron system. Using standard first order

A. Zangwill

1981-01-01

393

Capacitive interactions and Kondo effect tuning in double quantum impurity systems

NASA Astrophysics Data System (ADS)

We present a study of the correlated transport regimes of a double quantum impurity system with mutual capacitive interactions. Such system can be implemented by a double quantum dot arrangement or by a quantum dot and nearby quantum point contact, with independently connected sets of metallic terminals. Many-body spin correlations arising within each dot-lead subsystem give rise to the Kondo effect under appropriate conditions. The otherwise independent Kondo ground states may be modified by the capacitive coupling, decisively modifying the ground state of the double quantum impurity system. We analyze this coupled system through variational methods and the numerical renormalization group technique. Our results reveal a strong dependence of the coupled system ground state on the electron-hole asymmetries of the individual subsystems, as well as on their hybridization strengths to the respective reservoirs. The electrostatic repulsion produced by the capacitive coupling produces an effective shift of the individual energy levels toward higher energies, with a stronger effect on the "shallower" subsystem (that closer to resonance with the Fermi level), potentially pushing it out of the Kondo regime and dramatically changing the transport properties of the system. The effective remote gating that this entails is found to depend nonlinearly on the capacitive coupling strength, as well as on the independent subsystem levels. The analysis we present here of this mutual interaction should be important to fully characterize transport through such coupled systems.

Ruiz-Tijerina, David A.; Vernek, E.; Ulloa, Sergio E.

2014-07-01

394

Path integrals in configuration space in weakly relativistic many-body theory

The functional method of quantizing weakly relativistic theories is considered. It is shown that in the general case of systems with Lagrangian nonquadratic in the velocities the Green's function can be represented in the form of the regular part of a path integral in the configuration space. On this basis, a functional formulation of equilibrium statistical mechanics that does not require a Hamiltonian description of the system is developed. The results are used to determine the free energy of a system of charged particles described by the Darwin Lagrangian.

Blazhievskii, L.F.

1986-09-01

395

3>2>1: Investigation of Single Particle and Many Body Physics in Dual-Gated 1,2,3 Layers of Graphene

NASA Astrophysics Data System (ADS)

Graphene, a two-dimensional honeycomb lattice of carbon atoms, has become the hottest platform for condensed matter physics and a promising next generation electronic material. The band structures of single-, bi- and tri-layer graphene differ dramatically, yet all host chiral charge carriers with competing symmetries (such as spin, valley and orbital) that may be broken spontaneously or by an external field. In this thesis we present comprehensive transport studies on double-gated single-, bi- and tri-layer graphene, which lead to further insight into single particle and many-body physics in this fascinating 2D system. A prevailing motif in these studies was the use of suspended structures with the aim to eliminate extrinsic factors such as disorder, which obscure intrinsic physical phenomena. Our efforts were most successful with dual gated suspended bilayer graphene where an unprecedented sample quality was achieved. These studies are discussed in chapters six through nine. First, we focus on the observation of a spontaneous zero conductance gap at the charge neutrality point with zero out of plane electric and magnetic fields. By applying fields this gap can be closed with an electric field of either polarity, and grows monotonically with increasing magnetic field. These findings provide insight into the underlying symmetries of this correlated electron phenomena. Secondly, we performed a systematic study using several devices of the minimum conductivity at charge neutrality. These devices fall into one group with finite, and another with zero minimum conductivity. Because the second group consists of only high quality samples we surmise this insulating state is intrinsic. By tuning temperature we found this gapped insulating state has a critical temperature suggesting a phase transition between insulating and conducting states. Additionally, the transition is tuned by disorder, out-of-plane electric field, or carrier density, suggesting a quantum phase transition. Lastly, we study broken symmetry QH states at finite carrier density in the presence of zero and finite out of plane electric field. We find minute electric fields, which are commonly induced in single gated samples, significantly affect the broken symmetry states. Hence this study with zero electric field is the first genuine measurement of these states.

Velasco, Jairo

396

Quantum identification system Miloslav Dusek,1

identification system combining a classical identification procedure and quantum key distribution is proposed only once and the distribution of a common secret string is achieved by means of quantum keyQuantum identification system Miloslav Dusek,1 Ondrej Haderka,2,1 Martin Hendrych,2,1 and Robert

Dusek, Miloslav

397

STUDENT PAPER: Solving the Many-Body Polarization Problem on GPUs: Application to MOFs

NSDL National Science Digital Library

Massively Parallel Monte Carlo, an in-house computer code available at http://code.google.com/p/mpmc/, has been successfully utilized to simulate interactions between gas phase sorbates and various metal-organic materials. In this regard, calculations involving polarizability were found to be critical, and computationally expensive. Although GPGPU routines have increased the speed of these calculations immensely, in its original state, the program was only able to leverage a GPUÃÂÃÂs power on small systems. In order to study larger and evermore complex systems, the program model was modified such that limitations related to system size were relaxed while performance was either increased or maintained. In this project, parallel programming techniques learned from the Blue Waters Undergraduate Petascale Education Program were employed to increase the efficiency and expand the utility of this code.

Tudor, Brant; Space, Brian

398

naturally to non-Markovian equations of motion for the two-time correlators. Memory functions are identified-Zernike equation for classical fluids undergoing overdamped Brow- nian motion and driven out of equilibrium, and hence for all thermodynamic properties of the system.2 Even simple, short-ranged approximations to c

Schmidt, Matthias

399

Classification of gapped symmetric phases in one-dimensional spin systems

Quantum many-body systems divide into a variety of phases with very different physical properties. The questions of what kinds of phases exist and how to identify them seem hard, especially for strongly interacting systems. ...

Chen, Xie

400

Recently we have shown that the free energy for pore formation induced by antimicrobial peptides contains a term representing peptide-peptide interactions mediated by membrane thinning. This many-body effect gives rise to the cooperative concentration dependence of peptide activities. Here we performed oriented circular dichroism and x-ray diffraction experiments to study the lipid dependence of this many-body effect. In particular we studied the correlation between lipid's spontaneous curvature and peptide's threshold concentration for pore formation by adding phosphatidylethanolamine and lysophosphocholine to phosphocholine bilayers. Previously it was argued that this correlation exhibited by magainin and melittin supported the toroidal model for the pores. Here we found similar correlations exhibited by melittin and alamethicin. We found that the main effect of varying the spontaneous curvature of lipid is to change the degree of membrane thinning, which in turn influences the threshold concentration for pore formation. We discuss how to interpret the lipid dependence of membrane thinning. PMID:16150963

Lee, Ming-Tao; Hung, Wei-Chin; Chen, Fang-Yu; Huang, Huey W.

2005-01-01

401

Significance of higher-order many-body interaction energy terms in water clusters and bulk water

The magnitudes of the two- and three-body energy terms and their contribution to the interaction energy are computed for different water trimer arrangements at the second- to the fourth-order many-body perturbation (MP2 and MP4) levels of theory. Configurations in which the water molecules act as proton donor-acceptors, double acceptors and double donors were considered. The energy separation between the ‘cyclic’

Sotiris S. Xantheas

1996-01-01

402

NASA Astrophysics Data System (ADS)

The assumption that hormonal feedback regulates ovarian follicle growth is used to formulate a many-body problem in which interactions are spatially independent. This mechanism of interaction is shown to be sufficient to account for the regulation of ovulation number. A method is also developed to test if this assumption is consistent with the observed spatial distribution of follicles in the Rhesus monkey ovary.

Michael Lacker, H.; Percus, Allon

1991-06-01

403

Relativistic multireference many-body perturbation theory calculations have been performed on sulfurlike ions as benchmarks for high-accuracy treatment of multiple open-shell ions with as many as six valence shell electrons. Term energies of the 46 excited states arising from the 3s23p4 , 3s3p5 , and 3s23p33d configurations in ions of the sulfur isoelectronic sequence (Z=26-32) are evaluated to high accuracy. Transition

Yasuyuki Ishikawa; Marius J. Vilkas

2008-01-01

404

The utility of many-body decompositions for the accurate basis set extrapolation of ab initio data

We present a powerful new technique for the extrapolation of ab initio data based on many-body decompositions. Using the new methodology and subtle modifications of the standard correlation consistent basis sets, the H+H2 barrier height is estimated at 9.603 kcal\\/mol with a precision of about 0.003 kcal\\/mol; this extremely accurate result is all the more striking as it can be

Steven L. Mielke; Bruce C. Garrett; Kirk A. Peterson

1999-01-01

405

System identification for passive linear quantum systems

System identification is a key enabling component for the implementation of quantum technologies, including quantum control. In this paper, we consider the class of passive linear input-output systems, and investigate several basic questions: (1) which parameters can be identified? (2) Given sufficient input-output data, how do we reconstruct system parameters? (3) How can we optimize the estimation precision by preparing appropriate input states and performing measurements on the output? We show that minimal systems can be identified up to a unitary transformation on the modes, and systems satisfying a Hamiltonian connectivity condition called "infecting" are completely identifiable. We propose a frequency domain design based on a Fisher information criterion, for optimizing the estimation precision for coherent input state. As a consequence of the unitarity of the transfer function, we show that the Heisenberg limit with respect to the input energy can be achieved using non-classical input states.

Madalin Guta; Naoki Yamamoto

2013-03-15

406

Accurate double many-body expansion potential energy surface for the 2(1)A' state of N2O.

An accurate double many-body expansion potential energy surface is reported for the 2(1)A' state of N2O. The new double many-body expansion (DMBE) form has been fitted to a wealth of ab initio points that have been calculated at the multi-reference configuration interaction level using the full-valence-complete-active-space wave function as reference and the cc-pVQZ basis set, and subsequently corrected semiempirically via double many-body expansion-scaled external correlation method to extrapolate the calculated energies to the limit of a complete basis set and, most importantly, the limit of an infinite configuration interaction expansion. The topographical features of the novel potential energy surface are then examined in detail and compared with corresponding attributes of other potential functions available in the literature. Exploratory trajectories have also been run on this DMBE form with the quasiclassical trajectory method, with the thermal rate constant so determined at room temperature significantly enhancing agreement with experimental data. PMID:25173014

Li, Jing; Varandas, António J C

2014-08-28

407

Many-body state engineering using measurements and fixed unitary dynamics

NASA Astrophysics Data System (ADS)

We develop a scheme to prepare a desired state or subspace in high-dimensional Hilbert-spaces using repeated applications of a single static projection operator onto the desired target and fixed unitary dynamics. Benchmarks against other control schemes, performed on generic Hamiltonians and on Bose--Hubbard systems, establish the competitiveness of the method. As a concrete application of the control of mesoscopic atomic samples in optical lattices we demonstrate the near deterministic preparation of SchrÃ¶dinger cat states of all atoms residing on either the odd or the even sites.

Kock Pedersen, Mads; Sørensen, Jens Jakob W. H.; Tichy, Malte C.; Sherson, Jacob F.

2014-11-01

408

Many-body dynamic localization of strongly correlated electrons in ac-driven Hubbard lattices.

In the framework of the Hubbard model, it is shown that approximate dynamic localization for strongly correlated electrons hopping on a one-dimensional lattice and driven by a high-frequency sinusoidal field can be realized provided that periodic ? phase slips are impressed into the sinusoidal field. A possible experimental demonstration of the proposed driving scheme is presented for a photonic model system of the two-particle Hubbard model, based on light transport in a square waveguide lattice with a sinusoidally curved optical axis. PMID:23032640

Longhi, S

2012-10-31

409

Finite temperature calculations for the bulk properties of strange star using a many-body approach

We have considered a hot strange star matter, just after the collapse of a supernova, as a composition of strange, up and down quarks to calculate the bulk properties of this system at finite temperature with the density dependent bag constant. To parameterize the density dependent bag constant, we use our results for the lowest order constrained variational (LOCV) calculations of asymmetric nuclear matter. Our calculations for the structure properties of the strange star at different temperatures indicate that its maximum mass decreases by increasing the temperature. We have also compared our results with those of a fixed value of the bag constant. It can be seen that the density dependent bag constant leads to higher values of the maximum mass and radius for the strange star.

Bordbar, G H; Zamani, A

2011-01-01

410

Finite temperature calculations for the bulk properties of strange star using a many-body approach

We have considered a hot strange star matter, just after the collapse of a supernova, as a composition of strange, up and down quarks to calculate the bulk properties of this system at finite temperature with the density dependent bag constant. To parameterize the density dependent bag constant, we use our results for the lowest order constrained variational (LOCV) calculations of asymmetric nuclear matter. Our calculations for the structure properties of the strange star at different temperatures indicate that its maximum mass decreases by increasing the temperature. We have also compared our results with those of a fixed value of the bag constant. It can be seen that the density dependent bag constant leads to higher values of the maximum mass and radius for the strange star.

G. H. Bordbar; A. Poostforush; A. Zamani

2011-03-12

411

NASA Astrophysics Data System (ADS)

The demands of cutting-edge science are driving the need for larger and faster computing resources. With the rapidly growing scale of computing systems and the prospect of technologically disruptive architectures to meet these needs, scientists face the challenge of effectively using complex computational resources to advance scientific discovery. Multi-disciplinary collaborating networks of researchers with diverse scientific backgrounds are needed to address these complex challenges. The UNEDF SciDAC collaboration of nuclear theorists, applied mathematicians, and computer scientists is developing a comprehensive description of nuclei and their reactions that delivers maximum predictive power with quantified uncertainties. This paper describes UNEDF and identifies attributes that classify it as a successful computational collaboration. We illustrate significant milestones accomplished by UNEDF through integrative solutions using the most reliable theoretical approaches, most advanced algorithms, and leadership-class computational resources.

Nam, H.; Stoitsov, M.; Nazarewicz, W.; Bulgac, A.; Hagen, G.; Kortelainen, M.; Maris, P.; Pei, J. C.; Roche, K. J.; Schunck, N.; Thompson, I.; Vary, J. P.; Wild, S. M.

2012-12-01

412

NBODY Codes: Numerical Simulations of Many-body (N-body) Gravitational Interactions

NASA Astrophysics Data System (ADS)

I review the development of direct N-body codes at Cambridge over nearly 40 years, highlighting the main stepping stones. The first code (NBODY1) was based on the simple concepts of a force polynomial combined with individual time steps, where numerical problems due to close encounters were avoided by a softened potential. Fortuitously, the elegant Kustaanheimo-Stiefel two-body regularization soon permitted small star clusters to be studied (NBODY3). Subsequent extensions to unperturbed three-body and four-body regularization proved beneficial in dealing with multiple interactions. Investigations of larger systems became possible with the Ahmad-Cohen neighbor scheme which was used more than 20 years ago for expanding universe models of 4000 galaxies (NBODY2). Combining the neighbor scheme with the regularization procedures enabled more realistic star clusters to be considered (NBODY5). After a period of simulations with no apparent technical progress, chain regularization replaced the treatment of compact subsystems (NBODY3, NBODY5). More recently, the Hermite integration method provided a major advance and has been implemented on the special-purpose HARP computers (NBODY4) together with an alternative version for workstations and supercomputers (NBODY6). These codes also include a variety of algorithms for stellar evolution based on fast lookup functions. The treatment of primordial binaries contains efficient procedures for chaotic two-body motion as well as tidal circularization, and special attention is paid to hierarchical systems and their stability. This family of N-body codes constitutes a powerful tool for dynamical simulations which is freely available to the astronomical community, and the massive effort owes much to collaborators.

Aarseth, Sverre J.

2011-02-01

413

Entanglement and Quantum Phase Transition in a One-Dimensional System of quantum Dots with Disorder

Entanglement and Quantum Phase Transition in a One-Dimensional System of quantum Dots with Disorder We study the entanglement of formation and quantum phase transition in a one-dimensional quantum dots, quantum computer based on quantum dots is a prominent one[9, 10]. Quantum dots are clusters of atoms

Kais, Sabre

414

Could nanostructure be unspeakable quantum system?

Heisenberg, Bohr and others were forced to renounce on the description of the objective reality as the aim of physics because of the paradoxical quantum phenomena observed on the atomic level. The contemporary quantum mechanics created on the base of their positivism point of view must divide the world into speakable apparatus which amplifies microscopic events to macroscopic consequences and unspeakable quantum system. Examination of the quantum phenomena corroborates the confidence expressed by creators of quantum theory that the renunciation of realism should not apply on our everyday macroscopic world. Nanostructures may be considered for the present as a boundary of realistic description for all phenomena including the quantum one.

V. V. Aristov; A. V. Nikulov

2010-06-28

415

Simulation of n-qubit quantum systems. V. Quantum measurements

NASA Astrophysics Data System (ADS)

The FEYNMAN program has been developed during the last years to support case studies on the dynamics and entanglement of n-qubit quantum registers. Apart from basic transformations and (gate) operations, it currently supports a good number of separability criteria and entanglement measures, quantum channels as well as the parametrizations of various frequently applied objects in quantum information theory, such as (pure and mixed) quantum states, hermitian and unitary matrices or classical probability distributions. With the present update of the FEYNMAN program, we provide a simple access to (the simulation of) quantum measurements. This includes not only the widely-applied projective measurements upon the eigenspaces of some given operator but also single-qubit measurements in various pre- and user-defined bases as well as the support for two-qubit Bell measurements. In addition, we help perform generalized and POVM measurements. Knowing the importance of measurements for many quantum information protocols, e.g., one-way computing, we hope that this update makes the FEYNMAN code an attractive and versatile tool for both, research and education. New version program summaryProgram title: FEYNMAN Catalogue identifier: ADWE_v5_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWE_v5_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 27 210 No. of bytes in distributed program, including test data, etc.: 1 960 471 Distribution format: tar.gz Programming language: Maple 12 Computer: Any computer with Maple software installed Operating system: Any system that supports Maple; the program has been tested under Microsoft Windows XP and Linux Classification: 4.15 Catalogue identifier of previous version: ADWE_v4_0 Journal reference of previous version: Comput. Phys. Commun. 179 (2008) 647 Does the new version supersede the previous version?: Yes Nature of problem: During the last decade, the field of quantum information science has largely contributed to our understanding of quantum mechanics, and has provided also new and efficient protocols that are used on quantum entanglement. To further analyze the amount and transfer of entanglement in n-qubit quantum protocols, symbolic and numerical simulations need to be handled efficiently. Solution method: Using the computer algebra system Maple, we developed a set of procedures in order to support the definition, manipulation and analysis of n-qubit quantum registers. These procedures also help to deal with (unitary) logic gates and (nonunitary) quantum operations and measurements that act upon the quantum registers. All commands are organized in a hierarchical order and can be used interactively in order to simulate and analyze the evolution of n-qubit quantum systems, both in ideal and noisy quantum circuits. Reasons for new version: Until the present, the FEYNMAN program supported the basic data structures and operations of n-qubit quantum registers [1], a good number of separability and entanglement measures [2], quantum operations (noisy channels) [3] as well as the parametrizations of various frequently applied objects, such as (pure and mixed) quantum states, hermitian and unitary matrices or classical probability distributions [4]. With the current extension, we here add all necessary features to simulate quantum measurements, including the projective measurements in various single-qubit and the two-qubit Bell basis, and POVM measurements. Together with the previously implemented functionality, this greatly enhances the possibilities of analyzing quantum information protocols in which measurements play a central role, e.g., one-way computation. Running time: Most commands require ?10 seconds of processor time on a Pentium 4 processor with ?2 GHz RAM or newer, if they work with quantum registers with five or less qubits. Moreover, about 5-20 MB of working memory is typically n

Radtke, T.; Fritzsche, S.

2010-02-01

416

Quantum Coherence Effects in Novel Quantum Optical Systems

Optical response of an active medium can substantially be modified when coherent superpositions of states are excited, that is, when systems display quantum coherence and interference. This has led to fascinating applications in atomic and molecular...

Sete, Eyob Alebachew

2012-10-19

417

We study the distribution of the Schmidt coefficients of the reduced density matrix of a quantum system in a pure state. By applying general methods of statistical mechanics, we introduce a fictitious temperature and a partition function and translate the problem in terms of the distribution of the eigenvalues of random matrices. We investigate the appearance of two phase transitions, one at a positive temperature, associated with very entangled states, and one at a negative temperature, signaling the appearance of a significant factorization in the many-body wave function. We also focus on the presence of metastable states (related to two-dimensional quantum gravity) and study the finite size corrections to the saddle point solution.

De Pasquale, A. [Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); MECENAS, Universita Federico II di Napoli, Via Mezzocannone 8, I-80134 Napoli (Italy); Facchi, P. [INFN, Sezione di Bari, I-70126 Bari (Italy); Dipartimento di Matematica, Universita di Bari, I-70125 Bari (Italy); Parisi, G. [Dipartimento di Fisica, Universita di Roma 'La Sapienza', Piazzale Aldo Moro 2, I-00185 Roma (Italy); Centre for Statistical Mechanics and Complexity (SMC), CNR-INFM, I-00185 Roma, Italy INFN Sezione di Roma, I-00185 Roma (Italy); Pascazio, S. [Dipartimento di Fisica, Universita di Bari, I-70126 Bari (Italy); INFN, Sezione di Bari, I-70126 Bari (Italy); Scardicchio, A. [Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, I-34014 Trieste (Italy); INFN, Sezione di Trieste, I-34014 Trieste (Italy)

2010-05-15

418

Non-equilibrium Fractional Quantum Hall state of light

We investigate the quantum dynamics of systems involving small numbers of strongly interacting photons. Specifically, we develop an efficient method to investigate such systems when they are externally driven with a coherent field. Furthermore, we show how to quantify the many-body quantum state of light via correlation functions. Finally, we apply this method to two strongly interacting cases: the Bose-Hubbard and fractional quantum Hall models, and discuss an implementation of these ideas in atom-photon system.

Mohammad Hafezi; Mikhail D. Lukin; Jacob M. Taylor

2013-01-07

419

Quantum teleportation in one-dimensional quantum dots system Hefeng Wang, Sabre Kais *

Quantum teleportation in one-dimensional quantum dots system Hefeng Wang, Sabre Kais * Department of quantum teleportation protocol based on one-dimensional quantum dots system. Three quantum dots with three electrons are used to perform teleportation, the unknown qubit is encoded using one electron spin on quantum

Kais, Sabre

420

Quantum Teleportation in Quantum Dots System Hefeng Wang and Sabre Kais

Quantum Teleportation in Quantum Dots System Hefeng Wang and Sabre Kais Department of Chemistry of quantum teleportation protocol based on one-dimensional quantum dots system. Three quantum dots with three electrons are used to perform teleportation, the unknown qubit is encoded using one electron spin on quantum

Kais, Sabre

421

Indistinguishability of states for composite quantum system

We consider the states of composite system from quantum probabilistic amplitude superposition, and define the local indistinguishability (LID) and nonlocal indistinguishability (NLID). For pure states, the NLID is the same as nonlocal coherence. NLID can be considered as the measure of entanglement. LID can be considered as the measure of quantum correlation. From this respect, entanglement, which must have probabilistic amplitude superposition between product basis, is explicitly different from other quantum correlation. LID and NLID are also generalized to multipartite cases. These results are useful in the exploration of the distinctive quantum feature of quantum systems.

Chengjun Wu; Junhui Li; Bin Luo; Hong Guo

2014-05-06

422

This is the final report of a two-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have obtained a description of symmetry of the order parameter and pairing state in high-Tc superconductors. They developed a theory of ferromagnetic instability of Fermi-liquid. They have conducted an experimental investigation of the intermetallic compounds and Zintl-type compound. They investigated the properties of Cu-0 ladders. They have developed the theory of liftshitz tails in superconductors. They have conducted a number of summer workshops.

Balatsky, A.V. [Los Alamos National Lab., NM (United States); Scalapino, D. [Univ. of California, Santa Barbara, CA (United States); Wilkins, J. [Ohio State Univ., Columbus, OH (United States); Pines, D. [Univ. of Illinois, Urbana, IL (United States); Bedell, K. [Boston Coll., Chestnut Hill, MA (United States); Schrieffer, J.R.; Fisk, Z.

1998-12-01

423

Applications of Feedback Control in Quantum Systems

We give an introduction to feedback control in quantum systems, as well as an overview of the variety of applications which have been explored to date. This introductory review is aimed primarily at control theorists unfamiliar with quantum mechanics, but should also be useful to quantum physicists interested in applications of feedback control. We explain how feedback in quantum systems differs from that in traditional classical systems, and how in certain cases the results from modern optimal control theory can be applied directly to quantum systems. In addition to noise reduction and stabilization, an important application of feedback in quantum systems is adaptive measurement, and we discuss the various applications of adaptive measurements. We finish by describing specific examples of the application of feedback control to cooling and state-preparation in nano-electro-mechanical systems and single trapped atoms.

Kurt Jacobs

2006-05-02

424

System design for a long-line quantum repeater

We present a new control algorithm and system design for a network of quantum repeaters, and outline the end- to-end protocol architecture. Such a network will create long- distance quantum states, supporting quantum key distribution as well as distributed quantum computation. Quantum repeaters improve the reduction of quantum-communication throughput with distance from exponential to polynomial. Because a quantum state cannot

Rodney Van Meter; Thaddeus D. Ladd; W. J. Munro; Kae Nemoto

2009-01-01

425

NASA Astrophysics Data System (ADS)

A complete fourth-order many-body perturbation theory calculation of the dipole moment and dipole polarizability tensor is carried out for the FH molecule. Different approximations for the reduced resolvent operator are studied. Both the SD MBPT and SDQ MBPT schemes are found to give similar results. However, the fourth-order correlation corrections are dominated by the contribution of triple substitutions which is by no means negligible. The importance of a systematic treatment of all intermediate states in truncated MBPT schemes is discussed.

Diercksen, Geerd H. F.; Kellö, Vladimir; Sadley, Andrzej J.

1983-03-01

426

Quantum Speed Limits in Open System Dynamics

NASA Astrophysics Data System (ADS)

Bounds to the speed of evolution of a quantum system are of fundamental interest in quantum metrology, quantum chemical dynamics, and quantum computation. We derive a time-energy uncertainty relation for open quantum systems undergoing a general, completely positive, and trace preserving evolution which provides a bound to the quantum speed limit. When the evolution is of the Lindblad form, the bound is analogous to the Mandelstam-Tamm relation which applies in the unitary case, with the role of the Hamiltonian being played by the adjoint of the generator of the dynamical semigroup. The utility of the new bound is exemplified in different scenarios, ranging from the estimation of the passage time to the determination of precision limits for quantum metrology in the presence of dephasing noise.

del Campo, A.; Egusquiza, I. L.; Plenio, M. B.; Huelga, S. F.

2013-02-01

427

We estimate polarizabilities of atoms in molecules without electron density, using a Voronoi tesselation approach instead of conventional density partitioning schemes. The resulting atomic dispersion coefficients are calculated, as well as many-body dispersion effects on intermolecular potential energies. We also estimate contributions from multipole electrostatics and compare them to dispersion. We assess the performance of the resulting intermolecular interaction model from dispersion and electrostatics for more than 1300 neutral and charged, small organic molecular dimers. Applications to water clusters, the benzene crystal, the anti-cancer drug ellipticine-intercalated between two Watson-Crick DNA base pairs, as well as six macro-molecular host-guest complexes highlight the potential of this method and help to identify points of future improvement. The mean absolute error made by the combination of static electrostatics with many-body dispersion reduces at larger distances, while it plateaus for two-body dispersion, in conflict with the common assumption that the simple 1/R(6) correction will yield proper dissociative tails. Overall, the method achieves an accuracy well within conventional molecular force fields while exhibiting a simple parametrization protocol. PMID:25053295

Bereau, Tristan; von Lilienfeld, O Anatole

2014-07-21

428

NASA Astrophysics Data System (ADS)

We estimate polarizabilities of atoms in molecules without electron density, using a Voronoi tesselation approach instead of conventional density partitioning schemes. The resulting atomic dispersion coefficients are calculated, as well as many-body dispersion effects on intermolecular potential energies. We also estimate contributions from multipole electrostatics and compare them to dispersion. We assess the performance of the resulting intermolecular interaction model from dispersion and electrostatics for more than 1300 neutral and charged, small organic molecular dimers. Applications to water clusters, the benzene crystal, the anti-cancer drug ellipticine—intercalated between two Watson-Crick DNA base pairs, as well as six macro-molecular host-guest complexes highlight the potential of this method and help to identify points of future improvement. The mean absolute error made by the combination of static electrostatics with many-body dispersion reduces at larger distances, while it plateaus for two-body dispersion, in conflict with the common assumption that the simple 1/R6 correction will yield proper dissociative tails. Overall, the method achieves an accuracy well within conventional molecular force fields while exhibiting a simple parametrization protocol.

Bereau, Tristan; von Lilienfeld, O. Anatole

2014-07-01

429

Many-body effects on the structures and stability of Ba(2+)Xen (n = 1-39, 54) clusters.

The structures and relative stabilities of mixed Ba(2+)Xen (n = 1-39, 54) clusters have been theoretically studied using basin-hopping global optimization. Analytical potential energy surfaces were constructed from ab initio or experimental data, assuming either purely additive interactions or including many-body polarization effects and the mutual contribution of self-consistent induced dipoles. For both models the stable structures are characterized by the barium cation being coated by a shell of xenon atoms, as expected from simple energetic arguments. Icosahedral packing is dominantly found, the exceptional stability of the icosahedral motif at n = 12 being further manifested at the size n = 32 where the basic icosahedron is surrounded by a dodecahedral cage, and at n = 54 where the transition to multilayer Mackay icosahedra has occurred. Interactions between induced dipoles generally tend to decrease the Xe-Xe binding, leading to different solvation patterns at small sizes but also favoring polyicosahedral growth. Besides attenuating relative energetic stability, many-body effects affect the structures by expanding the clusters by a few percents and allowing them to deform more. PMID:25338897

Abdessalem, Kawther; Habli, Héla; Ghalla, Houcine; Yaghmour, Saud Jamil; Calvo, Florent; Oujia, Brahim

2014-10-21

430

Many-body effects on the structures and stability of Ba2+Xen (n = 1-39, 54) clusters

NASA Astrophysics Data System (ADS)

The structures and relative stabilities of mixed Ba2+Xen (n = 1-39, 54) clusters have been theoretically studied using basin-hopping global optimization. Analytical potential energy surfaces were constructed from ab initio or experimental data, assuming either purely additive interactions or including many-body polarization effects and the mutual contribution of self-consistent induced dipoles. For both models the stable structures are characterized by the barium cation being coated by a shell of xenon atoms, as expected from simple energetic arguments. Icosahedral packing is dominantly found, the exceptional stability of the icosahedral motif at n = 12 being further manifested at the size n = 32 where the basic icosahedron is surrounded by a dodecahedral cage, and at n = 54 where the transition to multilayer Mackay icosahedra has occurred. Interactions between induced dipoles generally tend to decrease the Xe-Xe binding, leading to different solvation patterns at small sizes but also favoring polyicosahedral growth. Besides attenuating relative energetic stability, many-body effects affect the structures by expanding the clusters by a few percents and allowing them to deform more.

Abdessalem, Kawther; Habli, Héla; Ghalla, Houcine; Yaghmour, Saud Jamil; Calvo, Florent; Oujia, Brahim

2014-10-01

431

Quantum Lie Systems and Integrability Conditions

NASA Astrophysics Data System (ADS)

The theory of Lie systems has recently been applied to Quantum Mechanics and additionally some integrability conditions for Lie systems of differential equations have also recently been analysed from a geometric perspective. In this paper we use both developments to obtain a geometric theory of integrability in Quantum Mechanics and we use it to provide a series of non-trivial integrable quantum mechanical models and to recover some known results from our unifying point of view.

Cariñena, José F.; de Lucas, Javier

432

Predictive Information for Quantum Bio-Systems

NASA Astrophysics Data System (ADS)

We consider the evolution of a quantum bio-system that interacts with an external environment in a stochastic manner. We ask an important question: when can a bio-system be more predictive to a changing environment? We prove that the non-predictive information for a driven quantum bio-system is lower bounded by the change in the quantum correlation and upper bounded by the entropy production in the system and the environment. We argue that for a system to have more predictive information, it must retain the quantum correlation. This shows that at a fundamental level if a biological system has to be energetically efficient, it must minimize the loss of quantum correlation.

Pati, Arun Kumar

2014-07-01

433

Nematic valley ordering in quantum Hall systems

The interplay between quantum Hall ordering and spontaneously broken ``internal'' symmetries in two-dimensional electron systems with spin or pseudospin degrees of freedom gives rise to a variety of interesting phenomena, including novel phases, phase transitions, and topological excitations. Here we develop a theory of broken-symmetry quantum Hall states, applicable to a class of multivalley systems, where the symmetry at issue

D. A. Abanin; S. A. Parameswaran; S. A. Kivelson; S. L. Sondhi

2010-01-01

434

Parameterizing density matrices for composite quantum systems

A parametrization of density operators for bipartite quantum systems is proposed. It is based on the particular parametrization of the unitary group found recently by Jarlskog. It is expected that this parametrization will find interesting applications in the study of quantum properties of many partite systems.

Erwin Bruening; Dariusz Chruscinski; Francesco Petruccione

2008-10-14

435

Quantum discord for a two-parameter class of states in $2 \\otimes d$ quantum systems

Quantum discord witnesses the nonclassicality of quantum states even when there is no entanglement in these quantum states. This type of quantum correlation also has some interesting and significant applications in quantum information processing. Quantum discord has been evaluated explicitly only for certain class of two-qubit states. We extend the previous studies to $2 \\otimes d$ quantum systems and derive an analytical expression for quantum discord for a two-parameter class of states for $d \\geq 3$. We compare quantum discord, classical correlation, and entanglement for qubit-qutrit systems to demonstrate that different measures of quantum correlation are not identical and conceptually different.

Mazhar Ali

2010-08-24

436

Quantum hacking: attacking practical quantum key distribution systems

Quantum key distribution (QKD) can, in principle, provide unconditional security based on the fundamental laws of physics. Unfortunately, a practical QKD system may contain overlooked imperfections and violate some of the assumptions in a security proof. Here, we report two types of eavesdropping attacks against a practical QKD system. The first one is \\

Bing Qi; Chi-Hang Fred Fung; Yi Zhao; Xiongfeng Ma; Kiyoshi Tamaki; Christine Chen; Hoi-Kwong Lo

2007-01-01

437

Understanding electronic systems in semiconductor quantum dots

NASA Astrophysics Data System (ADS)

Systems of confined electrons are found everywhere in nature in the form of atoms where the orbiting electrons are confined by the Coulomb attraction of the nucleus. Advancement of nanotechnology has, however, provided us with an alternative way to confine electrons by using artificial confining potentials. A typical structure of this nature is the quantum dot, a nanoscale system which consists of few confined electrons. There are many types of quantum dots ranging from self-assembled to miniaturized semiconductor quantum dots. In this work we are interested in electrostatically confined semiconductor quantum dot systems where the electrostatic confining potential that traps the electrons is generated by external electrodes, doping, strain or other factors. A large number of semiconductor quantum dots of this type are fabricated by applying lithographically patterned gate electrodes or by etching on two-dimensional electron gases in semiconductor heterostructures. Because of this, the whole structure can be treated as a confined two-dimensional electron system. Quantum confinement profoundly affects the way in which electrons interact with each other, and external parameters such as a magnetic field. Since a magnetic field affects both the orbital and the spin motion of the electrons, the interplay between quantum confinement, electron-electron correlation effects and the magnetic field gives rise to very interesting physical phenomena. Thus, confined systems of electrons in a semiconductor quantum dot represent a unique opportunity to study fundamental quantum theories in a controllable atomic-like setup. In this work, we describe some common theoretical models which are used to study confined systems of electrons in a two-dimensional semiconductor quantum dot. The main emphasis of the work is to draw attention to important physical phenomena that arise in confined two-dimensional electron systems under various quantum regimes.

Ciftja, Orion

2013-11-01

438

Typical Hamiltonian liquids display exponential "Lyapunov instability", also called "sensitive dependence on initial conditions". Although Hamilton's equations are thoroughly time-reversible the forward and backward Lyapunov instabilities can differ, qualitatively. In numerical work the expected forward/backward pairing of Lyapunov exponents is also occasionally violated. To illustrate we consider many-body inelastic collisions in two space dimensions. Two mirror-image colliding crystallites can either bounce, or not, giving rise to a single liquid drop, or to several smaller droplets, depending upon the initial kinetic energy and the interparticle forces. The difference between the forward and backward evolutionary instabilities of these problems can be correlated with dissipation and with the Second Law of Thermodynamics. Accordingly these asymmetric stabilities of Hamilton's equations can provide an "Arrow of Time". We illustrate these facts for two small crystallites colliding so as to make a warm liquid....

Hoover, Wm G

2014-01-01

439

NASA Astrophysics Data System (ADS)

The electric dipole moment (? ?), dipole polarizability (? ?,?) and second (? ????) dipole hyperpolarizability of ammonia were obtained from finite-field self-consistent-field (SCF) and complete fourth-order many-body perturbation theory (MP4) calculations. With z as the C3 axis, the following SDQ-MP4 results are reported: ? z = -0.6034 e a0, ? = 14.01 and ?? = 1.59 e2a20E-1h, ? = 30.47 and ?? = 8.87 e3a30E-2h, ? = 3864 e4a40E-3h. The triplets (T4) contribution to the fourth-order correction for the above properties is estimated to be 0.0083 e a0, 0.29 and 0.25 e2a20E-1h, 4.42 and 5.43 e3a30E-2h, 311 e4a40E-3h, respectively.

Maroulis, George

1992-07-01

440

The spin-rotational Hamiltonian parameters A{sub ||} and A{sub perpendicular} for the BaF molecule are calculated using four-component relativistic spinors at the second-order many-body perturbation theory (MBPT) level via the Z-vector technique. The second-order MBPT is applied to assess the accuracy of the computed hyperfine-structure constants before studying the problem with the state-of-the-artcoupled cluster with single and double excitations (CCSD) method which is highly accurate but computationally more expensive than MBPT. The hyperfine-structure constants A and A{sub d} resulted from these calculations agree favorably well with experimental findings and with other correlated calculations. The convergence behavior of A and A{sub d} with respect to the number of active orbitals used in the perturbative calculations suggests that our estimated A and A{sub d} values should be accurate.

Nayak, Malaya K.; Chaudhuri, Rajat K. [Theoretical Chemistry Section, Chemistry Group, Bhabha Atomic Research Centre, Trombay Mumbai 400085 (India); Indian Institute of Astrophysics, Bangalore 560034 (India)

2011-02-15