9,444 research outputs found
Photon subtracted states and enhancement of nonlocality in the presence of noise
We address nonlocality of continuous variable systems in the presence of
dissipation and noise. Three nonlocality tests have been considered, based on
the measurement of displaced-parity, field-quadrature and pseudospin-operator,
respectively. Nonlocality of twin beam has been investigated, as well as that
of its non-Gaussian counterparts obtained by inconclusive subtraction of
photons. Our results indicate that: i) nonlocality of twin beam is degraded but
not destroyed by noise; ii) photon subtraction enhances nonlocality in the
presence of noise, especially in the low-energy regime.Comment: 12 pages, 7 figure
A criterion for entanglement in two two-level systems
We prove a necessary and sufficient condition for the occurrence of
entanglement in two two-level systems, simple enough to be of experimental
interest. Our results are illustrated in the context of a spin star system
analyzing the exact entanglement evolution of the central couple of spins.Comment: 4 pages, Submitted to Physical Review Letter
Letter from Charles Cola, former Yonkers City Councilman, to Geraldine Ferraro
Congratulatory letter from Charles A. Cola, former Yonkers City Councilman and former Republican, to Geraldine Ferraro. Cola also writes on behalf of the North Yonkers Preservation & Development Corporation. Included are a copy of a letter written by Cola to President Ronald Reagan, outlining his reasons for leaving the Republican Party, plus a newspaper clipping of an article about Cola, and a data entry sheet.https://ir.lawnet.fordham.edu/vice_presidential_campaign_correspondence_1984_new_york/1226/thumbnail.jp
Dynamic update of a virtual cell for programming and safe monitoring of an industrial robot
A hardware/software architecture for robot motion planning and on-line safe monitoring has been developed with the objective to assure high flexibility in production control, safety for workers and machinery, with user-friendly interface. The architecture, developed using Microsoft Robotics Developers Studio and implemented for a six-dof COMAU NS 12 robot, established a bidirectional communication between the robot controller and a virtual replica of the real robotic cell. The working space of the real robot can then be easily limited for safety reasons by inserting virtual objects (or sensors) in such a virtual environment. This paper investigates the possibility to achieve an automatic, dynamic update of the virtual cell by using a low cost depth sensor (i.e., a commercial Microsoft Kinect) to detect the presence of completely unknown objects, moving inside the real cell. The experimental tests show that the developed architecture is able to recognize variously shaped mobile objects inside the monitored area and let the robot stop before colliding with them, if the objects are not too small
W-like states of N uncoupled spins 1/2
The exact dynamics of a disordered spin star system, describing a central
spin coupled to N distinguishable and non interacting spins 1/2, is reported.
Exploiting their interaction with the central single spin system, we present
possible conditional schemes for the generation of W-like states, as well as of
well-defined angular momentum states, of the N uncoupled spins. We provide in
addition a way to estimate the coupling intensity between each of the N spins
and the central one. Finally the feasibility of our procedure is briefly
discussed.Comment: 8 pages, 2 figures, accepted for publication in European Physical
Journal Special Topic
Squeezed Fock state by inconclusive photon subtraction
We analyze in details the properties of the conditional state recently
obtained by J. Wenger, et al. [Phys. Rev. Lett. {\bf 92}, 153601 (2004)] by
means of inconclusive photon subtraction (IPS) on a squeezed vacuum state
. The IPS process can be characterized by two parameters: the IPS
transmissivity and the photodetection quantum efficiency . We
found that the conditional state approaches the squeezed Fock state
when , i.e., in the limit of single-photon
subtraction. For non-unit IPS transmissivity and efficiency, the conditioned
state remains close to the target state, {\em i.e.} shows a high fidelity for a
wide range of experimental parameters. The nonclassicality of the conditional
state is also investigated and a nonclassicality threshold on the IPS
parameters is derived.Comment: 10 pages, 7 figure
The optical companion to the binary millisecond pulsar J1824-2452H in the globular cluster M28
We report on the optical identification of the companion star to the
eclipsing millisecond pulsar PSR J1824-2452H in the galactic globular cluster
M28 (NGC 6626). This star is at only 0.2" from the nominal position of the
pulsar and it shows optical variability (~ 0.25 mag) that nicely correlates
with the pulsar orbital period. It is located on the blue side of the cluster
main sequence, ~1.5 mag fainter than the turn-off point. The observed light
curve shows two distinct and asymmetric minima, suggesting that the companion
star is suffering tidal distortion from the pulsar. This discovery increases
the number of non-degenerate MSP companions optically identified so far in
globular clusters (4 out of 7), suggesting that these systems could be a common
outcome of the pulsar recycling process, at least in dense environments where
they can be originated by exchange interactions.Comment: accepted for publication on ApJ, 17 pages, 5 figure
Horizontal-Branch Models and the Second-Parameter Effect. IV. The Case of M3 and Palomar 3
We present a detailed analysis of the "second-parameter pair" of globular
clusters M3 (NGC 5272) and Palomar 3. Our main results can be summarized as
follows: i) The horizontal-branch (HB) morphology of M3 is significantly bluer
in its inner regions (observed with the Hubble Space Telescope) than in the
cluster outskirts (observed from the ground), i.e., M3 has an internal second
parameter. Most plausibly the mass loss on the red giant branch (RGB) has been
more efficient in the inner than in the outer regions of the cluster. ii) The
dispersion in mass of the Pal 3 HB is found to be very small -- consistent with
zero -- and we argue that this is unlikely to be due to a statistical
fluctuation. It is this small mass dispersion that leads to the most apparent
difference in the HB morphologies of M3 and Pal 3. iii) The relative HB types
of M3 and Pal 3, as measured by mean colors or parameters involving the number
of blue, variable, and red HB stars, can easily be accounted for by a fairly
small difference in age between these clusters, of order 0.5-1 Gyr -- which is
in good agreement with the relative age measurement, based on the clusters'
turnoffs, by VandenBerg (2000).Comment: 20 pages, 12 figures, emulateapj5 style. The Astrophysical Journal,
in press. Figs. 1, 6, 9, 10 are in png format. The preprint (postscript
format) with full resolution (embedded) figures is available from
http://www.astro.virginia.edu/~mc6v
Finite frequency noise for edge states at filling factor
We investigate the properties of the finite frequency noise in a quantum
point contact geometry for the fractional quantum Hall state at filling factor
. The results are obtained in the framework of the Wen's hierarchical
model.
We show that the peak structure of the colored noise allows to discriminate
among different possible excitations involved in the tunneling. In particular,
optimal values of voltage and temperature are found in order to enhance the
visibility of the peak associated with the tunneling of a 2-agglomerate, namely
an excitation with charge double of the fundamental one associated to the
single quasiparticle.Comment: 5 pages, 1 figure, to be published in the Proceedings of the
Conference on the Frontiers of Quantum and Mesoscopic Thermodynamics (FQMT11
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