268 research outputs found
Measurement and Information Extraction in Complex Dynamics Quantum Computation
We address the problem related to the extraction of the information in the
simulation of complex dynamics quantum computation. Here we present an example
where important information can be extracted efficiently by means of quantum
simulations. We show how to extract efficiently the localization length, the
mean square deviation and the system characteristic frequency. We show how this
methods work on a dynamical model, the Sawtooth Map, that is characterized by
very different dynamical regimes: from near integrable to fully developed
chaos; it also exhibits quantum dynamical localization.Comment: 8 pages, 4 figures, Proceeding of "First International Workshop
DICE2002 - Piombino (Tuscany), (2002)
Lattice gauge theories simulations in the quantum information era
The many-body problem is ubiquitous in the theoretical description of
physical phenomena, ranging from the behavior of elementary particles to the
physics of electrons in solids. Most of our understanding of many-body systems
comes from analyzing the symmetry properties of Hamiltonian and states: the
most striking example are gauge theories such as quantum electrodynamics, where
a local symmetry strongly constrains the microscopic dynamics. The physics of
such gauge theories is relevant for the understanding of a diverse set of
systems, including frustrated quantum magnets and the collective dynamics of
elementary particles within the standard model. In the last few years, several
approaches have been put forward to tackle the complex dynamics of gauge
theories using quantum information concepts. In particular, quantum simulation
platforms have been put forward for the realization of synthetic gauge
theories, and novel classical simulation algorithms based on quantum
information concepts have been formulated. In this review we present an
introduction to these approaches, illustrating the basics concepts and
highlighting the connections between apparently very different fields, and
report the recent developments in this new thriving field of research.Comment: Pedagogical review article. Originally submitted to Contemporary
Physics, the final version will appear soon on the on-line version of the
journal. 34 page
Probing models of information spreading in social networks
We apply signal processing analysis to the information spreading in
scale-free network. To reproduce typical behaviors obtained from the analysis
of information spreading in the world wide web we use a modified SIS model
where synergy effects and influential nodes are taken into account. This model
depends on a single free parameter that characterize the memory-time of the
spreading process. We show that by means of fractal analysis it is possible
-from aggregated easily accessible data- to gain information on the memory time
of the underlying mechanism driving the information spreading process.Comment: 6 pages, 6 figure
Quantum Game of Life
We introduce a quantum version of the Game of Life and we use it to study the
emergence of complexity in a quantum world. We show that the quantum evolution
displays signatures of complex behaviour similar to the classical one, however
a regime exists, where the quantum Game of Life creates more complexity, in
terms of diversity, with respect to the corresponding classical reversible one
Density Matrix Renormalization Group for Dummies
We describe the Density Matrix Renormalization Group algorithms for time
dependent and time independent Hamiltonians. This paper is a brief but
comprehensive introduction to the subject for anyone willing to enter in the
field or write the program source code from scratch.Comment: 29 pages, 9 figures. Published version. An open source version of the
code can be found at http://qti.sns.it/dmrg/phome.htm
Quantum MERA Channels
Tensor networks representations of many-body quantum systems can be described
in terms of quantum channels. We focus on channels associated with the
Multi-scale Entanglement Renormalization Ansatz (MERA) tensor network that has
been recently introduced to efficiently describe critical systems. Our approach
allows us to compute the MERA correspondent to the thermodynamic limit of a
critical system introducing a transfer matrix formalism, and to relate the
system critical exponents to the convergence rates of the associated channels.Comment: 4 pages, 2 figure
Increasing entanglement through engineered disorder in the random Ising chain
The ground state entanglement entropy between block of sites in the random
Ising chain is studied by means of the Von Neumann entropy. We show that in
presence of strong correlations between the disordered couplings and local
magnetic fields the entanglement increases and becomes larger than in the
ordered case. The different behavior with respect to the uncorrelated
disordered model is due to the drastic change of the ground state properties.
The same result holds also for the random 3-state quantum Potts model.Comment: 4 pages, published version, a few typos correcte
Tensor networks for Lattice Gauge Theories and Atomic Quantum Simulation
We show that gauge invariant quantum link models, Abelian and non-Abelian,
can be exactly described in terms of tensor networks states. Quantum link
models represent an ideal bridge between high-energy to cold atom physics, as
they can be used in cold-atoms in optical lattices to study lattice gauge
theories. In this framework, we characterize the phase diagram of a (1+1)-d
quantum link version of the Schwinger model in an external classical background
electric field: the quantum phase transition from a charge and parity ordered
phase with non-zero electric flux to a disordered one with a net zero electric
flux configuration is described by the Ising universality class.Comment: 9 pages, 9 figures. Published versio
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