23,509 research outputs found
Evolution of the Chern-Simons Vortices
Based on the gauge potential decomposition theory and the -mapping
theory, the topological inner structure of the Chern-Simons-Higgs vortex has
been showed in detail. The evolution of CSH vortices is studied from the
topological properties of the Higgs scalar field. The vortices are found
generating or annihilating at the limit points and encountering, splitting or
merging at the bifurcation points of the scalar field Comment: 10 pages, 10 figure
Trapped ion quantum computation with transverse phonon modes
We propose a scheme to implement quantum gates on any pair of trapped ions
immersed in a large linear crystal, using interaction mediated by the
transverse phonon modes. Compared with the conventional approaches based on the
longitudinal phonon modes, this scheme is much less sensitive to ion heating
and thermal motion outside of the Lamb-Dicke limit thanks to the stronger
confinement in the transverse direction. The cost for such a gain is only a
moderate increase of the laser power to achieve the same gate speed. We also
show how to realize arbitrary-speed quantum gates with transverse phonon modes
based on simple shaping of the laser pulses.Comment: 5 page
Intrinsic charm content of the nucleon and charmness-nucleon sigma term
In the extended chiral constituent quark model, the intrinsic
content of the nucleon is investigated. The probabilities of the
quark-antiquark components in the nucleon wave functions are calculated by
taking the nucleon to be admixtures of three- and five-quark components, with
the relevant transitions handled {\it via} the P mechanism.
Predictions for the probability of the in the nucleon wave function
and the charmness-nucleon sigma term are presented. Our numerical results turn
out to be consistent with the predictions from various other approaches
reported in the literature.Comment: Accepted for publication in Phys. Rev.
Sequential inverse problems Bayesian principles and the\ud logistic map example
Bayesian statistics provides a general framework for solving inverse problems, but is not without interpretation and implementation problems. This paper discusses difficulties arising from the fact that forward models are always in error to some extent. Using a simple example based on the one-dimensional logistic map, we argue that, when implementation problems are minimal, the Bayesian framework is quite adequate. In this paper the Bayesian Filter is shown to be able to recover excellent state estimates in the perfect model scenario (PMS) and to distinguish the PMS from the imperfect model scenario (IMS). Through a quantitative comparison of the way in which the observations are assimilated in both the PMS and the IMS scenarios, we suggest that one can, sometimes, measure the degree of imperfection
Three-dimensional theory for interaction between atomic ensembles and free-space light
Atomic ensembles have shown to be a promising candidate for implementations
of quantum information processing by many recently-discovered schemes. All
these schemes are based on the interaction between optical beams and atomic
ensembles. For description of these interactions, one assumed either a
cavity-QED model or a one-dimensional light propagation model, which is still
inadequate for a full prediction and understanding of most of the current
experimental efforts which are actually taken in the three-dimensional free
space. Here, we propose a perturbative theory to describe the three-dimensional
effects in interaction between atomic ensembles and free-space light with a
level configuration important for several applications. The calculations reveal
some significant effects which are not known before from the other approaches,
such as the inherent mode-mismatching noise and the optimal mode-matching
conditions. The three-dimensional theory confirms the collective enhancement of
the signal-to-noise ratio which is believed to be one of the main advantage of
the ensemble-based quantum information processing schemes, however, it also
shows that this enhancement need to be understood in a more subtle way with an
appropriate mode matching method.Comment: 16 pages, 9 figure
Arbitrary-speed quantum gates within large ion crystals through minimum control of laser beams
We propose a scheme to implement arbitrary-speed quantum entangling gates on
two trapped ions immersed in a large linear crystal of ions, with minimal
control of laser beams. For gate speeds slower than the oscillation frequencies
in the trap, a single appropriately-detuned laser pulse is sufficient for
high-fidelity gates. For gate speeds comparable to or faster than the local ion
oscillation frequency, we discover a five-pulse protocol that exploits only the
local phonon modes. This points to a method for efficiently scaling the ion
trap quantum computer without shuttling ions.Comment: 4 page
Neutrinos, Weak Interactions, and r-process Nucleosynthesis
Two of the key issues in understanding the neutron-to-proton ratio in a
core-collapse supernova are discussed. One of these is the behavior of the
neutrino-nucleon cross sections as supernova energies. The other issue is the
many-body properties of the neutrino gas near the core when both one- and
two-body interaction terms are included.Comment: To be published in the Proceedings of "International Symposium on
Structure of Exotic Nuclei and Nuclear Forces (SENUF 06)", March 2006, Tokyo,
Japa
Entanglement-assisted transformation is asymptotically equivalent to multiple-copy transformation
We show that two ways of manipulation of quantum entanglement, namely,
entanglement-assisted local transformation [D. Jonathan and M. B. Plenio, Phys.
Rev. Lett. {\bf 83}, 3566 (1999)] and multiple-copy transformation [S.
Bandyopadhyay, V. Roychowdhury, and U. Sen, Phys. Rev. A {\bf 65}, 052315
(2002)], are equivalent in the sense that they can asymptotically simulate each
other's ability to implement a desired transformation from a given source state
to another given target state with the same optimal success probability. As a
consequence, this yields a feasible method to evaluate the optimal conversion
probability of an entanglement-assisted transformation.Comment: 5 pages, revtex4, references updated, no figures. A slightly shorter
version appears in PR
Measurement based entanglement under conditions of extreme photon loss
The act of measuring optical emissions from two remote qubits can entangle
them. By demanding that a photon from each qubit reaches the detectors, one can
ensure than no photon was lost. But the failure rate then rises quadratically
with loss probability. In [1] this resulted in 30 successes per billion
attempts. We describe a means to exploit the low grade entanglement heralded by
the detection of a lone photon: A subsequent perfect operation is quickly
achieved by consuming this noisy resource. We require only two qubits per node,
and can tolerate both path length variation and loss asymmetry. The impact of
photon loss upon the failure rate is then linear; realistic high-loss devices
can gain orders of magnitude in performance and thus support QIP.Comment: Contains an extension of the protocol that makes it robust against
asymmetries in path length and photon los
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