28,321 research outputs found
Direct estimation of functionals of density operators by local operations and classical communication
We present a method of direct estimation of important properties of a shared bipartite quantum state, within the "distant laboratories" paradigm, using only local operations and classical communication. We apply this procedure to spectrum estimation of shared states, and locally implementable structural physical approximations to incompletely positive maps. This procedure can also be applied to the estimation of channel capacity and measures of entanglement
Time-dependent Robin boundary conditions in the dynamical Casimir effect
Motivated by experiments in which moving boundaries are simulated by
time-dependent properties of static systems, we discuss the model of a massless
scalar field submitted to a time-dependent Robin boundary condition (BC) at a
static mirror in 1+1 dimensions. Using a perturbative approach, we compute the
spectral distribution of the created particles and the total particle creation
rate, considering a thermal state as the initial field state.Comment: 10 pages, 3 figures. To appear in proceedings of Conference on
Quantum Field Theory under the Influence of External Condition
Strategies for Optimize Off-Lattice Aggregate Simulations
We review some computer algorithms for the simulation of off-lattice clusters
grown from a seed, with emphasis on the diffusion-limited aggregation,
ballistic aggregation and Eden models. Only those methods which can be
immediately extended to distinct off-lattice aggregation processes are
discussed. The computer efficiencies of the distinct algorithms are compared.Comment: 6 pages, 7 figures and 3 tables; published at Brazilian Journal of
Physics 38, march, 2008 (http://www.sbfisica.org.br/bjp/files/v38_81.pdf
Performances of a Newly High Sensitive Trilayer F/Cu/F GMI Sensor
We have selected stress-annealed nanocrystalline Fe-based ribbons for
ferromagnetic/copper/ferromagnetic sensors exhibiting high magneto-impedance
ratio. Longitudinal magneto-impedance reaches 400% at 60 kHz and longitudinal
magneto-resistance increases up to 1300% around 200 kHz.Comment: 4 pages, 6 figures, Sensors and Actuators A (in review
The low-mass population of the Rho Ophiuchi molecular cloud
Star formation theories are currently divergent regarding the fundamental
physical processes that dominate the substellar regime. Observations of nearby
young open clusters allow the brown dwarf (BD) population to be characterised
down to the planetary mass regime, which ultimately must be accommodated by a
successful theory. We hope to uncover the low-mass population of the Rho
Ophiuchi molecular cloud and investigate the properties of the newly found
brown dwarfs. We use near-IR deep images (reaching completeness limits of
approximately 20.5 mag in J, and 18.9 mag in H and Ks) taken with the Wide
Field IR Camera (WIRCam) at the Canada France Hawaii Telescope (CFHT) to
identify candidate members of Rho Oph in the substellar regime. A spectroscopic
follow-up of a small sample of the candidates allows us to assess their
spectral type, and subsequently their temperature and membership. We select 110
candidate members of the Rho Ophiuchi molecular cloud, from which 80 have not
previously been associated with the cloud. We observed a small sample of these
and spectroscopically confirm six new brown dwarfs with spectral types ranging
from M6.5 to M8.25
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