850 research outputs found
Radiation Pressure Induced Einstein-Podolsky-Rosen Paradox
We demonstrate the appearance of Einstein-Podolsky-Rosen (EPR) paradox when a
radiation field impinges on a movable mirror. The, the possibility of a local
realism test within a pendular Fabry-Perot cavity is shown to be feasible.Comment: 4 pages ReVTeX, 1 eps figur
Constructing finite dimensional codes with optical continuous variables
We show how a qubit can be fault-tolerantly encoded in the
infinite-dimensional Hilbert space of an optical mode. The scheme is efficient
and realizable with present technologies. In fact, it involves two travelling
optical modes coupled by a cross-Kerr interaction, initially prepared in
coherent states, one of which is much more intense than the other. At the exit
of the Kerr medium, the weak mode is subject to a homodyne measurement and a
quantum codeword is conditionally generated in the quantum fluctuations of the
intense mode.Comment: 7 pages, 5 figure
An XMM-Newton View of the Radio Galaxy 3C 411
We present the first high signal-to-noise XMM-Newton observations of the
broad-line radio galaxy 3C 411. After fitting various spectral models, an
absorbed double power-law continuum and a blurred relativistic disk reflection
model (kdblur) are found to be equally plausible descriptions of the data.
While the softer power-law component (=2.11) of the double power-law
model is entirely consistent with that found in Seyfert galaxies (and hence
likely originates from a disk corona), the additional power law component is
very hard (=1.05); amongst the AGN zoo, only flat-spectrum radio
quasars have such hard spectra. Together with the very flat radio-spectrum
displayed by this source, we suggest that it should instead be classified as a
FSRQ. This leads to potential discrepancies regarding the jet inclination
angle, with the radio morphology suggesting a large jet inclination but the
FSRQ classification suggesting small inclinations. The kdblur model predicts an
inner disk radius of at most 20 r and relativistic reflection
A model independent approach to non dissipative decoherence
We consider the case when decoherence is due to the fluctuations of some
classical variable or parameter of a system and not to its entanglement with
the environment. Under few and quite general assumptions, we derive a
model-independent formalism for this non-dissipative decoherence, and we apply
it to explain the decoherence observed in some recent experiments in cavity QED
and on trapped ions.Comment: 12 pages, 3 figure
Different realizations of tomographic principle in quantum state measurement
We establish a general principle for the tomographic approach to quantum
state reconstruction, till now based on a simple rotation transformation in the
phase space, which allows us to consider other types of transformations. Then,
we will present different realizations of the principle in specific examples.Comment: 17 pages, Latex file, no figures, accepted by J. of Mod. Op
An outburst scenario for the X-ray spectral variability in 3C 111
We present a combined Suzaku and Swift BAT broad-band E=0.6-200keV spectral
analysis of three 3C 111 observations obtained in 2010. The data are well
described with an absorbed power-law continuum and a weak (R~0.2) cold
reflection component from distant material. We constrain the continuum cutoff
at E_c~150-200keV, which is in accordance with X-ray Comptonization corona
models and supports claims that the jet emission is only dominant at much
higher energies. Fe XXVI Ly\alpha emission and absorption lines are also
present in the first and second observations, respectively. The modelling and
interpretation of the emission line is complex and we explore three
possibilities. If originating from ionized disc reflection, this should be
emitted at r_in> 50r_g or, in the lamp-post configuration, the illuminating
source should be at a height of h> 30r_g over the black hole. Alternatively,
the line could be modeled with a hot collisionally ionized plasma with
temperature kT = 22.0^{+6.1}_{-3.2} keV or a photo-ionized plasma with
log\xi=4.52^{+0.10}_{-0.16} erg s^{-1} cm and column density N_H > 3x10^23
cm^{-2}. However, the first and second scenarios are less favored on
statistical and physical grounds, respectively. The blue-shifted absorption
line in the second observation can be modelled as an ultra-fast outflow (UFO)
with ionization parameter log\xi=4.47^{+0.76}_{-0.04} erg s^{-1} cm, column
density N_H=(5.3^{+1.8}_{-1.3})x 10^{22} cm^{-2} and outflow velocity v_out =
0.104+/-0.006 c. Interestingly, the parameters of the photo-ionized emission
model remarkably match those of the absorbing UFO. We suggest an outburst
scenario in which an accretion disc wind, initially lying out of the line of
sight and observed in emission, then crosses our view to the source and it is
observed in absorption as a mildly-relativistic UFO.Comment: Accepted for publication in MNARS on July 1st 201
Density Matrix From Photon Number Tomography
We provide a simple analytic relation which connects the density operator of
the radiation field with the number probabilities. The problem of
experimentally "sampling" a general matrix elements is studied, and the
deleterious effects of nonunit quantum efficiency in the detection process are
analyzed showing how they can be reduced by using the squeezing technique. The
obtained result is particulary useful for intracavity field reconstruction
states.Comment: LATEX,6 pages,accepted by Europhysics Letter
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