4,886 research outputs found
Analysis of the entanglement between two individual atoms using global Raman rotations
Making use of the Rydberg blockade, we generate entanglement between two
atoms individually trapped in two optical tweezers. In this paper we detail the
analysis of the data and show that we can determine the amount of entanglement
between the atoms in the presence of atom losses during the entangling
sequence. Our model takes into account states outside the qubit basis and
allows us to perform a partial reconstruction of the density matrix describing
the two atom state. With this method we extract the amount of entanglement
between pairs of atoms still trapped after the entangling sequence and measure
the fidelity with respect to the expected Bell state. We find a fidelity
for the 62% of atom pairs remaining in the traps at
the end of the entangling sequence
Systematic analysis of pT -distributions in p + p collisions
A systematic analysis of transverse momentum distribution of hadrons produced
in ultra-relativistic p + p collisions is presented. We investigate the
effective temperature and the entropic parameter from the non-extensive
thermodynamic theory of strong interaction. We conclude that the existence of a
limiting effective temperature and of a limiting entropic parameter is in
accordance with experimental data.Comment: 9 pages, 5 figure
Entanglement of two individual neutral atoms using Rydberg blockade
We report the generation of entanglement between two individual Rb
atoms in hyperfine ground states and which are held in
two optical tweezers separated by 4 m. Our scheme relies on the Rydberg
blockade effect which prevents the simultaneous excitation of the two atoms to
a Rydberg state. The entangled state is generated in about 200 ns using pulsed
two-photon excitation. We quantify the entanglement by applying global Raman
rotations on both atoms. We measure that 61% of the initial pairs of atoms are
still present at the end of the entangling sequence. These pairs are in the
target entangled state with a fidelity of 0.75.Comment: text revised, with additional reference
Nonextensive statistical effects in the quark-gluon plasma formation at relativistic heavy-ion collisions energies
We investigate the relativistic equation of state of hadronic matter and
quark-gluon plasma at finite temperature and baryon density in the framework of
the non-extensive statistical mechanics, characterized by power-law quantum
distributions. We impose the Gibbs conditions on the global conservation of
baryon number, electric charge and strangeness number. For the hadronic phase,
we study an extended relativistic mean-field theoretical model with the
inclusion of strange particles (hyperons and mesons). For the quark sector, we
employ an extended MIT-Bag model. In this context we focus on the relevance of
non-extensive effects in the presence of strange matter.Comment: 12 pages, 5 figure
Fluctuations of g-factors in metal nanoparticles: Effects of electron-electron interaction and spin-orbit scattering
We investigate the combined effect of spin-orbit scattering and
electron-electron interactions on the probability distribution of -factors
of metal nanoparticles. Using random matrix theory, we find that even a
relatively small interaction strength %(ratio of exchange constant and mean
level %spacing \spacing ) significantly increases -factor
fluctuations for not-too-strong spin-orbit scattering (ratio of spin-orbit rate
and single-electron level spacing 1/\tau_{\rm so} \spacing \lesssim 1), and
leads to the possibility to observe -factors larger than two.Comment: RevTex, 2 figures inserte
The imprints of superstatistics in multiparticle production processes
We provide an update of the overview of imprints of Tsallis nonextensive
statistics seen in a multiparticle production processes. They reveal an
ubiquitous presence of power law distributions of different variables
characterized by the nonextensivity parameter q > 1. In nuclear collisions one
additionally observes a q-dependence of the multiplicity fluctuations
reflecting the finiteness of the hadronizing source. We present sum rules
connecting parameters q obtained from an analysis of different observables,
which allows us to combine different kinds of fluctuations seen in the data and
analyze an ensemble in which the energy (E), temperature (T) and multiplicity
(N) can all fluctuate. This results in a generalization of the so called
Lindhard's thermodynamic uncertainty relation. Finally, based on the example of
nucleus-nucleus collisions (treated as a quasi-superposition of nucleon-nucleon
collisions) we demonstrate that, for the standard Tsallis entropy with degree
of nonextensivity q < 1, the corresponding standard Tsallis distribution is
described by q' = 2 - q > 1.Comment: 12 pages, 3 figures. Based on invited talk given by Z.Wlodarczyk at
SigmaPhi2011 conference, Larnaka, Cyprus, 11-15 July 2011. To be published in
Cent. Eur. J. Phys. (2011
Entanglement of two individual atoms using the Rydberg blockade
We report on our recent progress on the manipulation of single rubidium atoms
trapped in optical tweezers and the generation of entanglement between two
atoms, each individually trapped in neighboring tweezers. To create an
entangled state of two atoms in their ground states, we make use of the Rydberg
blockade mechanism. The degree of entanglement is measured using global
rotations of the internal states of both atoms. Such internal state rotations
on a single atom are demonstrated with a high fidelity.Comment: Proceeding of the 19th International Conference on Laser Spectroscopy
ICOLS 2009, 7-13 June 2009, Hokkaido, Japa
Diffusion of spheres in isotropic and nematic suspensions of rods
Diffusion of a small tracer sphere (apoferritin) in isotropic and nematic networks [of fd virus] is discussed. For a tracer sphere that is smaller than the mesh size of the network, screened hydrodynamic interactions between the sphere and the network determine its diffusion coefficient. A theory is developed for such interactions as well as their relation to the long-time self-diffusion coefficient. Fluorescence correlation spectroscopy measurements on mixtures of apoferritin and fd virus are presented. The long-time self-diffusion coefficient of apoferritin is measured as a function of the fd-virus concentration, both in the isotropic and nematic state, in directions parallel and perpendicular to the nematic director. The hydrodynamic screening length of the fd-virus network as a function of fd concentration is obtained by combining these experimental data with the theory. Surprisingly, the screening length increases with increasing concentration in nematic networks. This is due to the increase in the degree of alignment, which apparently leads to a strong increase of the screening length. Hydrodynamic screening is thus strongly diminished by alignment. A self-consistent calculation of the screening length does not work at higher concentrations, probably due to the strong variation of the typical incident flow fields over the contour of a rod
Cognitive control: Easy to identify but hard to define
Cognitive control is easy to identify in its effects, but difficult to grasp conceptually. This creates somewhat of a puzzle: Is cognitive control a bona fide process or an epiphenomenon that merely exists in the mind of the observer? The topiCS special edition on cognitive control presents a broad set of perspectives on this issue and helps to clarify central conceptual and empirical challenges confronting the field. Our commentary provides a summary of and critical response to each of the papers. © 2011 Cognitive Science Society, Inc
Can cosmic strangelets reach the earth?
The mechanism for the propagation of strangelets with low baryon number
through the atmosphere of the Earth has been explored. It has been shown that
under suitable initial conditions, such strangelets may indeed reach depths
near mountain altitudes with mass numbers and charges close to the observed
values in cosmic ray experiments.Comment: RevTeX text, with 3 encoded eps figures. To appear in Physical Review
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