3,677 research outputs found
Frozen and Invariant Quantum Discord under Local Dephasing Noise
In this chapter, we intend to explore and review some remarkable dynamical
properties of quantum discord under various different open quantum system
models. Specifically, our discussion will include several concepts connected to
the phenomena of time invariant and frozen quantum discord. Furthermore, we
will elaborate on the relation of these two phenomena to the non-Markovian
features of the open system dynamics and to the usage of dynamical decoupling
protocols.Comment: 29 pages, 8 figure
Metal-insulator transition and glassy behavior in two-dimensional electron systems
Studies of low-frequency resistance noise demonstrate that glassy freezing
occurs in a two-dimensional electron system in silicon in the vicinity of the
metal-insulator transition (MIT). The width of the metallic glass phase, which
separates the 2D metal and the (glassy) insulator, depends strongly on
disorder, becoming extremely small in high-mobility (low-disorder) samples. The
glass transition is manifested by a sudden and dramatic slowing down of the
electron dynamics, and by a very abrupt change to the sort of statistics
characteristic of complicated multistate systems. In particular, the behavior
of the second spectrum, an important fourth-order noise statistic, indicates
the presence of long-range correlations between fluctuators in the glassy
phase, consistent with the hierarchical picture of glassy dynamics.Comment: Contribution to conference on "Noise as a tool for studying
materials" (SPIE), Santa Fe, New Mexico, June 2003; 15 pages, 12 figs.
(includes some low-quality figs; send e-mail to get high-quality figs.
Exploring complex networks via topological embedding on surfaces
We demonstrate that graphs embedded on surfaces are a powerful and practical
tool to generate, characterize and simulate networks with a broad range of
properties. Remarkably, the study of topologically embedded graphs is
non-restrictive because any network can be embedded on a surface with
sufficiently high genus. The local properties of the network are affected by
the surface genus which, for example, produces significant changes in the
degree distribution and in the clustering coefficient. The global properties of
the graph are also strongly affected by the surface genus which is constraining
the degree of interwoveness, changing the scaling properties from
large-world-kind (small genus) to small- and ultra-small-world-kind (large
genus). Two elementary moves allow the exploration of all networks embeddable
on a given surface and naturally introduce a tool to develop a statistical
mechanics description. Within such a framework, we study the properties of
topologically-embedded graphs at high and low `temperatures' observing the
formation of increasingly regular structures by cooling the system. We show
that the cooling dynamics is strongly affected by the surface genus with the
manifestation of a glassy-like freezing transitions occurring when the amount
of topological disorder is low.Comment: 18 pages, 7 figure
Transduction of DNA information through water and electromagnetic waves
The experimental conditions by which electromagnetic signals (EMS) of low
frequency can be emitted by diluted aqueous solutions of some bacterial and
viral DNAs are described. That the recorded EMS and nanostructures induced in
water carry the DNA information (sequence) is shown by retrieval of that same
DNA by classical PCR amplification using the TAQ polymerase, including both
primers and nucleotides. Moreover, such a transduction process has also been
observed in living human cells exposed to EMS irradiation. These experiments
suggest that coherent long range molecular interaction must be at work in water
so to allow the observed features. The quantum field theory analysis of the
phenomenon is presented.Comment: 10 pages, 6 figure
Low-temperature dynamical simulation of spin-boson systems
The dynamics of spin-boson systems at very low temperatures has been studied
using a real-time path-integral simulation technique which combines a
stochastic Monte Carlo sampling over the quantum fluctuations with an exact
treatment of the quasiclassical degrees of freedoms. To a large degree, this
special technique circumvents the dynamical sign problem and allows the
dynamics to be studied directly up to long real times in a numerically exact
manner. This method has been applied to two important problems: (1) crossover
from nonadiabatic to adiabatic behavior in electron transfer reactions, (2) the
zero-temperature dynamics in the antiferromagnetic Kondo region 1/2<K<1 where K
is Kondo's parameter.Comment: Phys. Rev. B (in press), 28 pages, 6 figure
Exploring Quantum Correlations from Discord to Entanglement
partially_open3sìQuantum correlations represent a fundamental tool for studies ranging from basic science to quantum technologies. Different non-classical correlations have been identified and studied, as entanglement and discord. In this Paper we explore experimentally the rich geometry of polarization Bell-diagonal states. By taking advantage of the statistical method of generation, the values of entanglement and discord along different trajectories in the space of the parameters of density matrix have been measured. The effects of sudden death of entanglement and complete "freeze" of discord were investigated in order to detect the domains with different domination of one type of quantum correlation against to other. A geometric interpretation for each considered phenomena is addressed. The observed good agreement between experiment and theory for all investigated trajectories ensures the reliability of this method.openMoreva, E.; Gramegna, M.; Yurischev, M.A.Moreva, E.; Gramegna, Marco; Yurischev, M. A
Exploring Quantum Correlations from Discord to Entanglement
Quantum correlations represent a fundamental tool for studies ranging from basic science to quantum technologies. Different non-classical correlations have been identified and studied, as entanglement and discord. In this Paper we explore experimentally the rich geometry of polarization Bell-diagonal states. By taking advantage of the statistical method of generation, the values of entanglement and discord along different trajectories in the space of the parameters of density matrix have been measured. The effects of sudden death of entanglement and complete "freeze" of discord were investigated in order to detect the domains with different domination of one type of quantum correlation against to other. A geometric interpretation for each considered phenomena is addressed. The observed good agreement between experiment and theory for all investigated trajectories ensures the reliability of this method
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