714 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
Multipartite entanglement generation and fidelity decay in disordered qubit systems
We investigate multipartite entanglement dynamics in disordered spin-1/2
lattice models exhibiting a transition from integrability to quantum chaos.
Borrowing from the recently introduced generalized entanglement framework, we
construct measures for correlations relative to arbitrary local and bi-local
spin observables, and show how they naturally signal the crossover between
distinct dynamical regimes. In particular, we find that the generation of
global entanglement is directly ruled by the local density of states in the
short time limit, whereas the asymptotic amount of entanglement is proportional
to the degree of delocalization of the chaotic many-body state. Our results are
relevant to the stability of quantum information in disordered quantum
computing hardware.Comment: 4 pages, 4 figure
One-dimensional many-body entangled open quantum systems with tensor network methods
We present a collection of methods to simulate entangled dynamics of open
quantum systems governed by the Lindblad equation with tensor network methods.
Tensor network methods using matrix product states have been proven very useful
to simulate many-body quantum systems and have driven many innovations in
research. Since the matrix product state design is tailored for closed
one-dimensional systems governed by the Schr\"odinger equation, the next step
for many-body quantum dynamics is the simulation of open quantum systems. We
review the three dominant approaches to the simulation of open quantum systems
via the Lindblad master equation: quantum trajectories, matrix product density
operators, and locally purified tensor networks. Selected examples guide
possible applications of the methods and serve moreover as a benchmark between
the techniques. These examples include the finite temperature states of the
transverse quantum Ising model, the dynamics of an exciton traveling under the
influence of spontaneous emission and dephasing, and a double-well potential
simulated with the Bose-Hubbard model including dephasing. We analyze which
approach is favorable leading to the conclusion that a complete set of all
three methods is most beneficial, push- ing the limits of different scenarios.
The convergence studies using analytical results for macroscopic variables and
exact diagonalization methods as comparison, show, for example, that matrix
product density operators are favorable for the exciton problem in our study.
All three methods access the same library, i.e., the software package Open
Source Matrix Product States, allowing us to have a meaningful comparison
between the approaches based on the selected examples. For example, tensor
operations are accessed from the same subroutines and with the same
optimization eliminating one possible bias in a comparison of such numerical
methods.Comment: 24 pages, 8 figures. Small extension of time evolution section and
moving quantum simulators to introduction in comparison to v
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
Entanglement production in chaotic quantum dots subject to spin-orbit coupling
We study numerically the production of orbital and spin entangled states in
chaotic quantum dots for non-interacting electrons. The introduction of
spin-orbit coupling permit us to identify signatures of time-reversal symmetry
correlations in the entanglement production previously unnoticed, resembling
weak-(anti)localization quantum corrections to the conductance. We find the
entanglement to be strongly dependent on spin-orbit coupling, showing universal
features for broken time-reversal and spin-rotation symmetries.Comment: 6 pages; extended versio
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