12,156 research outputs found
A Theory of Modern Transition Applied to Thailand
Modern Transition, Sector-Specific Complementarity, TFP and Inequality Dynamics
Growing network model for community with group structure
We propose a growing network model for a community with a group structure.
The community consists of individual members and groups, gatherings of members.
The community grows as a new member is introduced by an existing member at each
time step. The new member then creates a new group or joins one of the groups
of the introducer. We investigate the emerging community structure analytically
and numerically. The group size distribution shows a power law distribution for
a variety of growth rules, while the activity distribution follows an
exponential or a power law depending on the details of the growth rule. We also
present an analysis of empirical data from on the online communities, the
``Groups'' in \url{http://www.yahoo.com} and the ``Cafe'' in
\url{http://www.daum.net}, which shows a power law distribution for a wide
range of group sizes.Comment: 5 figures and 1 tabl
Band Gap Closing in a Synthetic Hall Tube of Neutral Fermions
We report the experimental realization of a synthetic three-leg Hall tube
with ultracold fermionic atoms in a one-dimensional optical lattice. The legs
of the synthetic tube are composed of three hyperfine spin states of the atoms,
and the cyclic inter-leg links are generated by two-photon Raman transitions
between the spin states, resulting in a uniform gauge flux penetrating
each side plaquette of the tube. Using quench dynamics, we investigate the band
structure of the Hall tube system for a commensurate flux .
Momentum-resolved analysis of the quench dynamics reveals that a critical point
of band gap closing as one of the inter-leg coupling strengths is varied, which
is consistent with a topological phase transition predicted for the Hall tube
system.Comment: 8 pages, 8 figure
Towards optimal quantum tomography with unbalanced homodyning
Balanced homodyning, heterodyning and unbalanced homodyning are the three
well-known sampling techniques used in quantum optics to characterize all
possible photonic sources in continuous-variable quantum information theory. We
show that for all quantum states and all observable-parameter tomography
schemes, which includes the reconstructions of arbitrary operator moments and
phase-space quasi-distributions, localized sampling with unbalanced homodyning
is always tomographically more powerful (gives more accurate estimators) than
delocalized sampling with heterodyning. The latter is recently known to often
give more accurate parameter reconstructions than conventional marginalized
sampling with balanced homodyning. This result also holds for realistic
photodetectors with subunit efficiency. With examples from first- through
fourth-moment tomography, we demonstrate that unbalanced homodyning can
outperform balanced homodyning when heterodyning fails to do so. This new
benchmark takes us one step towards optimal continuous-variable tomography with
conventional photodetectors and minimal experimental components.Comment: 9 pages, 4 figure
Effects of depolarizing quantum channels on BB84 and SARG04 quantum cryptography protocols
We report experimental studies on the effect of the depolarizing quantum
channel on weak-pulse BB84 and SARG04 quantum cryptography. The experimental
results show that, in real world conditions in which channel depolarization
cannot be ignored, BB84 should perform better than SARG04.Comment: 4 pages, 4 figure
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