654 research outputs found
Quantum correlations in a cluster-like system
We discuss a cluster-like 1D system with triplet interaction. We study the
topological properties of this system. We find that the degeneracy depends on
the topology of the system, and well protected against external local
perturbations. All these facts show that the system is topologically ordered.
We also find a string order parameter to characterize the quantum phase
transition. Besides, we investigate two-site correlations including
entanglement, quantum discord and mutual information. We study the different
divergency behaviour of the correlations. The quantum correlation decays
exponentially in both topological and magnetic phases, and diverges in reversed
power law at the critical point. And we find that in TQPT systems, the global
difference of topology induced by dimension can be reflected in local quantum
correlations.Comment: 7 pages, 6 figure
Tunneling Qubit Operation on a Protected Josephson Junction Array
We discuss a protected quantum computation process based on a hexagon
Josephson junction array. Qubits are encoded in the punctured array, which is
topologically protected. The degeneracy is related to the number of holes. The
topological degeneracy is lightly shifted by tuning the flux through specific
hexagons. We also show how to perform single qubit operation and basic quantum
gate operations in this system.Comment: 8 pages, 4 figures. The published version in Phys. Rev.,
A81(2010)01232
Quantum correlations in topological quantum phase transitions
We study the quantum correlations in a 2D system that possesses a topological
quantum phase transition. The quantumness of two-body correlations is measured
by quantum discord. We calculate both the correlation of two local spins and
that of an arbitrary spin with the rest of the lattice. It is notable that
local spins are classically correlated, while the quantum correlation is hidden
in the global lattice. This is different from other systems which are not
topologically orderd. Moreover, the mutual information and global quantum
discord show critical behavior in the topological quantum phase transition.Comment: 6 pages, 3 figure
decays in the pQCD approach
We calculate the CP averaged branching ratios and CP-violating asymmetries
for and
decays in the perturbative QCD (pQCD) approach here. The pQCD predictions for
the CP-averaged branching ratios are Br(B_s^0 \to \eta \eta) = \left
(14.2^{+18.0}_{-7.5}) \times 10^{-6}, Br(B_s^0 \to \eta \eta^\prime)= \left
(12.4 ^{+18.2}_{-7.0}) \times 10^{-6}, and Br(B_s^0 \to \eta^{\prime}
\eta^{\prime}) = \left (9.2^{+15.3}_{-4.9}) \times 10^{-6}, which agree well
with those obtained by employing the QCD factorization approach and also be
consistent with available experimental upper limits. The gluonic contributions
are small in size: less than 7% for and
decays, and around 18% for decay. The CP-violating
asymmetries for three decays are very small: less than 3% in magnitude.Comment: 11 pages, 1 ps figure, Revte
Spectra of Baryons Containing Two Heavy Quarks in Potential Model
In this work, we employ the effective vertices for interaction between
diquarks (scalar or axial-vector) and gluon where the form factors are derived
in terms of the B-S equation, to obtain the potential for baryons including a
light quark and a heavy diquark. The concerned phenomenological parameters are
obtained by fitting data of mesons instead of the heavy quarkonia.
The operator ordering problem in quantum mechanics is discussed. Our numerical
results indicate that the mass splitting between and
is very small and it is consistent with the heavy quark effective
theory (HQET).Comment: 16 page
Mobility gap in fractional quantum Hall liquids: Effects of disorder and layer thickness
We study the behavior of two-dimensional electron gas in the fractional
quantum Hall regime in the presence of finite layer thickness and correlated
disordered potential. Generalizing the Chern number calculation to many-body
systems, we determine the mobility gaps of fractional quantum Hall states based
on the distribution of Chern numbers in a microscopic model. We find excellent
agreement between experimentally measured activation gaps and our calculated
mobility gaps, when combining the effects of both disordered potential and
layer thickness. We clarify the difference between mobility gap and spectral
gap of fractional quantum Hall states and explain the disorder-driven collapse
of the gap and the subsequent transitions from the fractional quantum Hall
states to insulator.Comment: 13 pages, 8 figure
Tim-2 regulates T helper type 2 responses and autoimmunity
Identification of the T cell immunoglobulin mucin-domain containing (Tim) gene family introduced a new family of cell surface molecules that is involved in the regulation of immune responses. We previously demonstrated that Tim-3 is expressed on terminally differentiated T helper (Th)1 cells, and serves to regulate Th1 immune responses. Here, we describe the identification and function of Tim-2, a novel member of the Tim gene family. In contrast with Tim-3, we demonstrate that Tim-2 is expressed preferentially in differentiated Th2 cells. Blockade of the Tim-2/Tim-2 ligand interaction, by administration of soluble Tim-2 fusion protein (Tim-2 immunoglobulin [Ig]), results in T cell hyperproliferation and the production of Th2 cytokines. Administration of Tim-2 Ig during the induction phase reduces the severity of experimental autoimmune encephalomyelitis, a Th1-mediated autoimmune disease model of multiple sclerosis. We propose that Tim-2, an orthologue of human Tim-1, is critical for the regulation of Th2 responses during autoimmune inflammation
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