4,572 research outputs found
Entanglement generation via a completely mixed nuclear spin bath
We show that qubits coupled sequentially to a mesoscopic static completely
mixed spin bath via the Heisenberg interaction can become highly entangled.
Straightforward protocols for the generation of multipartite entangled
(Greenberger-Horne-Zeilinger-)states are presented. We show the feasibility of
an experimental realization in a quantum dot by the hyperfine interaction of an
electron with the nuclear spins.Comment: 4+pages, 3 figure
Online Bin Covering: Expectations vs. Guarantees
Bin covering is a dual version of classic bin packing. Thus, the goal is to
cover as many bins as possible, where covering a bin means packing items of
total size at least one in the bin.
For online bin covering, competitive analysis fails to distinguish between
most algorithms of interest; all "reasonable" algorithms have a competitive
ratio of 1/2. Thus, in order to get a better understanding of the combinatorial
difficulties in solving this problem, we turn to other performance measures,
namely relative worst order, random order, and max/max analysis, as well as
analyzing input with restricted or uniformly distributed item sizes. In this
way, our study also supplements the ongoing systematic studies of the relative
strengths of various performance measures.
Two classic algorithms for online bin packing that have natural dual versions
are Harmonic and Next-Fit. Even though the algorithms are quite different in
nature, the dual versions are not separated by competitive analysis. We make
the case that when guarantees are needed, even under restricted input
sequences, dual Harmonic is preferable. In addition, we establish quite robust
theoretical results showing that if items come from a uniform distribution or
even if just the ordering of items is uniformly random, then dual Next-Fit is
the right choice.Comment: IMADA-preprint-c
A bright, pulsed two-mode squeezer
We report the realization of a bright ultrafast two-mode squeezer based on
type II parametric downconversion (PDC) in periodically poled
(PP-KTP) waveguides. It produces a pulsed two-mode squeezed
vacuum state: a photon-number entangled pair of truly single-mode pulses or, in
terms of continuous variables quantum optics, a pulsed, single mode
Einstein-Podolsky-Rosen (EPR) state in the telecom regime. We prove the single
mode character of our source by measuring its correlation function
and demonstrate a mean photon number of up to 2.5 per pulse, equivalent to 11dB
of two-mode squeezing.Comment: 4 pages, 3 figure
Interquark Potential in Schrodinger Representation
Static charges are introduced in Yang-Mills theory via coupling to heavy
fermions. The states containing static color charges are constructed using
integration over gauge transformations. A functional representation for
interquark potential is obtained. This representation provides a simple
criterion for confinement.Comment: 9pp., Late
Recommended from our members
Deliverable 6.1: Radio spectrum, traffic engineering and resource management
Status and Future Perspectives for Lattice Gauge Theory Calculations to the Exascale and Beyond
In this and a set of companion whitepapers, the USQCD Collaboration lays out
a program of science and computing for lattice gauge theory. These whitepapers
describe how calculation using lattice QCD (and other gauge theories) can aid
the interpretation of ongoing and upcoming experiments in particle and nuclear
physics, as well as inspire new ones.Comment: 44 pages. 1 of USQCD whitepapers
A scalable PC-based parallel computer for lattice QCD
A PC-based parallel computer for medium/large scale lattice QCD simulations
is suggested. The Eotvos Univ., Inst. Theor. Phys. cluster consists of 137
Intel P4-1.7GHz nodes. Gigabit Ethernet cards are used for nearest neighbor
communication in a two-dimensional mesh. The sustained performance for
dynamical staggered(wilson) quarks on large lattices is around 70(110) GFlops.
The exceptional price/performance ratio is below $1/Mflop.Comment: 3 pages, 2 figures, Lattice2002(machines
Comments on the Instanton Size Distribution
By studying the non-linear effects of overlapping instanton pairs we address
difficulties in the identification of instanton distributions when the average
instanton size is comparable to the average distance. For the exact charge two
solution, we study how its parametrisation relates to a description in terms of
individual instantons. There exist two dual sets of parameters describing the
same charge two instanton solution. This duality implies the existence of a
minimal separation between two instantons. Conventionally used lattice
instanton finder algorithms based on the assumption of diluteness tend to
underestimate instanton sizes. Finally we numerically confirm this for
realistic parameters of the instanton liquid. The effect is enhanced by
parallel orientation in group space.Comment: LaTeX, 15 pages, 3 figure
Caveolin-3 differentially orchestrates cholinergic and serotonergic constriction of murine airways
The mechanisms of controlling airway smooth muscle (ASM) tone are of utmost clinical importance as inappropriate constriction is a hallmark in asthma and chronic obstructive pulmonary disease. Receptors for acetylcholine and serotonin, two relevant mediators in this context, appear to be incorporated in specialized, cholesterol-rich domains of the plasma membrane, termed caveolae due toĂÂ their invaginated shape. The structural protein caveolin-1 partly accounts for anchoring of these receptors. We here determined the role of the other major caveolar protein, caveolin-3 (cav-3), in orchestrating cholinergic and serotonergic ASM responses, utilizing newly generated cav-3 deficient mice. Cav-3 deficiency fully abrogated serotonin-induced constriction of extrapulmonary airways in organ baths while leaving intrapulmonary airways unaffected, as assessed in precision cut lung slices. The selective expression of cav-3 in tracheal, but not intrapulmonary bronchial epithelial cells, revealed by immunohistochemistry, might explain the differential effects of cav-3 deficiency on serotonergic ASM constriction. The cholinergic response of extrapulmonary airways was not altered, whereas a considerable increase was observed in cav-3Ăą -/- intrapulmonary bronchi. Thus, cav-3 differentially organizes serotonergic and cholinergic signaling in ASM through mechanisms that are specific for airways of certain caliber and anatomical position. This may allow for selective and site-specific intervention in hyperreactive states
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