14,181 research outputs found
Nonequilibrium thermal entanglement in three-qubit model
Making use of the master equation and effective Hamiltonian approach, we
investigate the steady state entanglement in a three-qubit model. Both
symmetric and nonsymmetric qubit-qubit couplings are considered. The system
(the three qubits) is coupled to two bosonic baths at different temperatures.
We calculate the steady state by the effective Hamiltonian approach and discuss
the dependence of the steady state entanglement on the temperatures and
couplings. The results show that for symmetric qubit-qubit couplings, the
entanglements between the nearest neighbor are equal, independent of the
temperatures of the two baths. The maximum of the entanglement arrives at
. For nonsymmetric qubit-qubit couplings, however, the situation is
totally different. The baths at different temperatures would benefit the
entanglement and the entanglements between the nearest neighbors are no longer
equal. By examining the probability distribution of each eigenstate in the
steady state, we present an explanation for these observations. These results
suggest that the steady entanglement can be controlled by the temperature of
the two baths.Comment: Comments are welcom
Effective Hamiltonian Approach to the Master Equation
A method of exactly solving the master equation is presented in this letter.
The explicit form of the solution is determined by the time evolution of a
composite system including an auxiliary system and the open system in question.
The effective Hamiltonian governing the time evolution of the composed system
are derived from the master equation. Two examples, the dissipative two-level
system and the damped harmonic oscillator, are presented to illustrate the
solving procedure.
PACS number(s): 05.30.-d, 05.40.+j, 42.50.CtComment: 4 pages, no figure
Probing dipolar effects with condensate shape oscillation
We discuss the low energy shape oscillations of a magnetic trapped atomic
condensate including the spin dipole interaction. When the nominal isotropic
s-wave interaction strength becomes tunable through a Feshbach resonance (e.g.
as for Rb atoms), anisotropic dipolar effects are shown to be detectable
under current experimental conditions [E. A. Donley {\it et al.}, Nature {\bf
412}, 295 (2001)].Comment: revised version, submitte
Towards a Notion of Distributed Time for Petri Nets
We set the ground for research on a timed extension of Petri nets where time parameters are associated with tokens and arcs carry constraints that qualify the age of tokens required for enabling. The novelty is that, rather than a single global clock, we use a set of unrelated clocks --- possibly one per place --- allowing a local timing as well as distributed time synchronisation. We give a formal definition of the model and investigate properties of local versus global timing, including decidability issues and notions of processes of the respective models
Electroluminescence from single nanowires by tunnel injection: an experimental study
We present a hybrid light-emitting diode structure composed of an n-type
gallium nitride nanowire on a p-type silicon substrate in which current is
injected along the length of the nanowire. The device emits ultraviolet light
under both bias polarities. Tunnel-injection of holes from the p-type substrate
(under forward bias) and from the metal (under reverse bias) through thin
native oxide barriers consistently explains the observed electroluminescence
behaviour. This work shows that the standard p-n junction model is generally
not applicable to this kind of device structure.Comment: 6 pages, 6 figure
Experimentally obtaining the Likeness of Two Unknown Quantum States on an NMR Quantum Information Processor
Recently quantum states discrimination has been frequently studied. In this
paper we study them from the other way round, the likeness of two quantum
states. The fidelity is used to describe the likeness of two quantum states.
Then we presented a scheme to obtain the fidelity of two unknown qubits
directly from the integral area of the spectra of the assistant qubit(spin) on
an NMR Quantum Information Processor. Finally we demonstrated the scheme on a
three-qubit quantum information processor. The experimental data are consistent
with the theoretical expectation with an average error of 0.05, which confirms
the scheme.Comment: 3 pages, 4 figure
Chemoenzymatic Probes for Detecting and Imaging Fucose-α(1-2)-galactose Glycan Biomarkers
The disaccharide motif fucose-α(1-2)-galactose (Fucα(1-2)Gal) is involved in many important physiological processes, such as learning and memory, inflammation, asthma, and tumorigenesis. However, the size and structural complexity of Fucα(1-2)Gal-containing glycans have posed a significant challenge to their detection. We report a new chemoenzymatic strategy for the rapid, sensitive detection of Fucα(1-2)Gal glycans. We demonstrate that the approach is highly selective for the Fucα(1-2)Gal motif, detects a variety of complex glycans and glycoproteins, and can be used to profile the relative abundance of the motif on live cells, discriminating malignant from normal cells. This approach represents a new potential strategy for biomarker detection and expands the technologies available for understanding the roles of this important class of carbohydrates in physiology and disease
Size Dependence In The Disordered Kondo Problem
We study here the role randomly-placed non-magnetic scatterers play on the
Kondo effect. We show that spin relaxation effects (with time )in the
vertex corrections to the Kondo self-energy lead to an exact cancellation of
the singular temperature dependence arising from the diffusion poles. For a
thin film of thickness and a mean-free path , disorder provides a
correction to the Kondo resistivity of the form
that explains both the disorder and sample-size depression of the Kondo effect
observed by Blachly and Giordano (PRB {\bf 51}, 12537 (1995)).Comment: 11 pages, LaTeX, 2 Postscript figure
Pair production of neutral Higgs bosons at the CERN Large Hadron Collider
We study the hadroproduction of two neutral Higgs bosons in the minimal
supersymmetric extension of the standard model, which provides a handle on the
trilinear Higgs couplings. We include the contributions from quark-antiquark
annihilation at the tree level and those from gluon-gluon fusion, which
proceeds via quark and squark loops. We list compact results for the tree-level
partonic cross sections and the squark loop amplitudes, and we confirm previous
results for the quark loop amplitudes. We quantitatively analyze the hadronic
cross sections at the CERN Large Hadron Collider assuming a favorable
supergravity-inspired scenario.Comment: 22 pages (Latex), 16 figures (Postscript). Discussion of theoretical
uncertainties and background processes added. Accepted for publication in
Phys. Rev.
Production of neutral scalar Higgs bosons at colliders
We study the production of neutral scalar (CP even) Higgs bosons in the
process by including supersymmetric corrections to the
dominant -channel photon exchange amplitude. In addition to the standard
model and fermion loops, there are substantial contributions from
chargino loops. For some cases, these contributions can exceed those of the
's and ordinary fermions. The cross sections in this channel are generally
one or two orders of magnitude larger than those in the related channel
.Comment: 12 pages RevTeX, 5 postscript figures included, uses epsf.st
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