1,093 research outputs found
Strong subadditivity inequality for quantum entropies and four-particle entanglement
Strong subadditivity inequality for a three-particle composite system is an
important inequality in quantum information theory which can be studied via a
four-particle entangled state. We use two three-level atoms in
configuration interacting with a two-mode cavity and the Raman adiabatic
passage technique for the production of the four-particle entangled state.
Using this four-particle entanglement, we study for the first time various
aspects of the strong subadditivity inequality.Comment: 5 pages, 3 figures, RevTeX4, submitted to PR
Separability and entanglement in 2x3xN composite quantum systems
The separability and entanglement of quantum mixed states in \Cb^2 \otimes
\Cb^3 \otimes \Cb^N composite quantum systems are investigated. It is shown
that all quantum states with positive partial transposes and rank
are separable.Comment: Latex, 15 page
Characterizing the entanglement of bipartite quantum systems
We derive a separability criterion for bipartite quantum systems which
generalizes the already known criteria. It is based on observables having
generic commutation relations. We then discuss in detail the relation among
these criteria.Comment: 5 pages, 2 figures. Revised versio
Entanglement and purity of two-mode Gaussian states in noisy channels
We study the evolution of purity, entanglement and total correlations of
general two--mode Gaussian states of continuous variable systems in arbitrary
uncorrelated Gaussian environments. The time evolution of purity, Von Neumann
entropy, logarithmic negativity and mutual information is analyzed for a wide
range of initial conditions. In general, we find that a local squeezing of the
bath leads to a faster degradation of purity and entanglement, while it can
help to preserve the mutual information between the modes.Comment: 10 pages, 8 figure
Climate, irrigation, and land cover change explain streamflow trends in countries bordering the northeast Atlantic
Attribution of trends in streamflow is complex, but essential, in identifying optimal management options for water resources. Disagreement remains on the relative role of climate change and human factors, including water abstractions and land cover change, in driving change in annual streamflow. We construct a very dense network of gauging stations (n = 1,874) from Ireland, the United Kingdom, France, Spain, and Portugal for the period of 1961–2012 to detect and then attribute changes in annual streamflow. Using regression‐based techniques, we show that climate (precipitation and atmospheric evaporative demand) explains many of the observed trends in northwest Europe, while for southwest Europe human disturbances better explain both temporal and spatial trends. For the latter, large increases in irrigated areas, agricultural intensification, and natural revegetation of marginal lands are inferred to be the dominant drivers of decreases in streamflow
Detecting genuine multipartite continuous-variable entanglement
We derive necessary conditions in terms of the variances of position and
momentum linear combinations for all kinds of separability of a multi-party
multi-mode continuous-variable state. Their violations can be sufficient for
genuine multipartite entanglement, provided the combinations contain both
conjugate variables of all modes. Hence a complete state determination, for
example by detecting the entire correlation matrix of a Gaussian state, is not
needed.Comment: 13 pages, 3 figure
Entanglement Sharing in the Two-Atom Tavis-Cummings Model
Individual members of an ensemble of identical systems coupled to a common
probe can become entangled with one another, even when they do not interact
directly. We investigate how this type of multipartite entanglement is
generated in the context of a system consisting of two two-level atoms
resonantly coupled to a single mode of the electromagnetic field. The dynamical
evolution is studied in terms of the entanglements in the different bipartite
partitions of the system, as quantified by the I-tangle. We also propose a
generalization of the so-called residual tangle that quantifies the inherent
three-body correlations in our tripartite system. This enables us to completely
characterize the phenomenon of entanglement sharing in the case of the two-atom
Tavis-Cummings model, a system of both theoretical and experimental interest.Comment: 11 pages, 4 figures, submitted to PRA, v3 contains corrections to
small error
X-ray standing wave and reflectometric characterization of multilayer structures
Microstructural characterization of synthetic periodic multilayers by x-ray
standing waves have been presented. It has been shown that the analysis of
multilayers by combined x-ray reflectometry (XRR) and x-ray standing wave (XSW)
techniques can overcome the deficiencies of the individual techniques in
microstructural analysis. While interface roughnesses are more accurately
determined by the XRR technique, layer composition is more accurately
determined by the XSW technique where an element is directly identified by its
characteristic emission. These aspects have been explained with an example of a
20 period Pt/C multilayer. The composition of the C-layers due to Pt
dissolution in the C-layers, PtC, has been determined by the XSW
technique. In the XSW analysis when the whole amount of Pt present in the
C-layers is assumed to be within the broadened interface, it l eads to larger
interface roughness values, inconsistent with those determined by the XRR
technique. Constraining the interface roughness values to those determined by
the XRR technique, requires an additional amount of dissolved Pt in the
C-layers to expl ain the Pt fluorescence yield excited by the standing wave
field. This analysis provides the average composition PtC of the
C-layers .Comment: 12 pages RevTex, 10 eps figures embedde
Neutrino Magnetic Moment and the Process
The contribution of a neutrino magnetic moment to the cross
section of the process has been
calculated and compared with the Standard Electroweak one. The radiative
process allows to reach low enough values of without the need to operate
at very small energies of recoil electrons. Regions in the phase space which
are more favourable to set bounds on are suggested.Comment: 25 pages (+11 figures, available upon request), Standard Late
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
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