806 research outputs found
Reduction of quantum noise in optical interferometers using squeezed light
We study the photon counting noise in optical interferometers used for
gravitational wave detection. In order to reduce quantum noise a squeezed
vacuum state is injected into the usually unused input port. Here, we
specifically investigate the so called `dark port case', when the beam splitter
is oriented close to 90{\deg} to the incoming laser beam, such that nearly all
photons go to one output port of the interferometer, and only a small fraction
of photons is seen in the other port (`dark port'). For this case it had been
suggested that signal amplification is possible without concurrent noise
amplification [R.Barak and Y.Ben-Aryeh, J.Opt.Soc.Am.B25(361)2008]. We show
that by injection of a squeezed vacuum state into the second input port,
counting noise is reduced for large values of the squeezing factor, however the
signal is not amplified. Signal strength only depends on the intensity of the
laser beam.Comment: 8 pages, 1 figur
Higher Derivative Quantum Gravity with Gauss-Bonnet Term
Higher derivative theory is one of the important models of quantum gravity,
renormalizable and asymptotically free within the standard perturbative
approach. We consider the renormalization group for this theory,
an approach which proved fruitful in models. A consistent
formulation in dimension requires taking quantum effects of the
topological term into account, hence we perform calculation which is more
general than the ones done before. In the special case we confirm a known
result by Fradkin-Tseytlin and Avramidi-Barvinsky, while contributions from
topological term do cancel. In the more general case of
renormalization group equations there is an extensive ambiguity related to
gauge-fixing dependence. As a result, physical interpretation of these
equations is not universal unlike we treat as a small parameter. In
the sector of essential couplings one can find a number of new fixed points,
some of them have no analogs in the case.Comment: LaTeX file, 30 pages, 5 figures. Several misprints in the
intermediate expressions correcte
Kinetic-inductance-limited reset time of superconducting nanowire photon counters
We investigate the recovery of superconducting NbN-nanowire photon counters
after detection of an optical pulse at a wavelength of 1550 nm, and present a
model that quantitatively accounts for our observations. The reset time is
found to be limited by the large kinetic inductance of these nanowires, which
forces a tradeoff between counting rate and either detection efficiency or
active area. Devices of usable size and high detection efficiency are found to
have reset times orders of magnitude longer than their intrinsic photoresponse
time.Comment: Submitted to Applied Physics Letter
Non-Commutative Batalin-Vilkovisky Algebras, Homotopy Lie Algebras and the Courant Bracket
We consider two different constructions of higher brackets. First, based on a
Grassmann-odd, nilpotent \Delta operator, we define a non-commutative
generalization of the higher Koszul brackets, which are used in a generalized
Batalin-Vilkovisky algebra, and we show that they form a homotopy Lie algebra.
Secondly, we investigate higher, so-called derived brackets built from
symmetrized, nested Lie brackets with a fixed nilpotent Lie algebra element Q.
We find the most general Jacobi-like identity that such a hierarchy satisfies.
The numerical coefficients in front of each term in these generalized Jacobi
identities are related to the Bernoulli numbers. We suggest that the definition
of a homotopy Lie algebra should be enlarged to accommodate this important
case. Finally, we consider the Courant bracket as an example of a derived
bracket. We extend it to the "big bracket" of exterior forms and multi-vectors,
and give closed formulas for the higher Courant brackets.Comment: 42 pages, LaTeX. v2: Added remarks in Section 5. v3: Added further
explanation. v4: Minor adjustments. v5: Section 5 completely rewritten to
include covariant construction. v6: Minor adjustments. v7: Added references
and explanation to Section
Ground state correlations and structure of odd spherical nuclei
It is well known that the Pauli principle plays a substantial role at low
energies because the phonon operators are not ideal boson operators.
Calculating the exact commutators between the quasiparticle and phonon
operators one can take into account the Pauli principle corrections. Besides
the ground state correlations due to the quasiparticle interaction in the
ground state influence the single particle fragmentation as well. In this
paper, we generalize the basic QPM equations to account for both mentioned
effects. As an illustration of our approach, calculations on the structure of
the low-lying states in Ba have been performed.Comment: 12 pages, 1 figur
Stable topological textures in a classical 2D Heisenberg model
We show that stable localized topological soliton textures (skyrmions) with
topological charge exist in a classical 2D Heisenberg
model of a ferromagnet with uniaxial anisotropy. For this model the soliton
exist only if the number of bound magnons exceeds some threshold value depending on and the effective anisotropy constant .
We define soliton phase diagram as the dependence of threshold energies and
bound magnons number on anisotropy constant. The phase boundary lines are
monotonous for both and , while the solitons with
reveal peculiar nonmonotonous behavior, determining the transition regime from
low to high topological charges. In particular, the soliton energy per
topological charge (topological energy density) achieves a minimum neither for
nor high charges, but rather for intermediate values or
.Comment: 8 pages, 4 figure
Coherent states of non-relativistic electron in magnetic-solenoid field
We construct coherent states of a nonrelativistic electron in the
magnetic-solenoid field, which is a superposition of the Aharonov-Bohm field
and a collinear uniform magnetic field. In the problem under consideration
there are two kind of coherent states, the first kind corresponds to classical
trajectories which embrace the solenoid and the second one to trajectories
which do not. Mean coordinates in the constructed coherent states are moving
along classical trajectories, the coherent states maintain their form under the
time evolution, and represent a complete set of functions, which can be useful
in semi classical calculations. In the absence of the Aharonov-Bohm filed these
states are reduced to the well-known in the case of uniform magnetic field
Malkin-Man'ko coherent states.Comment: 11 pages, version accepted for publication in J. Phys. A, 3 figures
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PdI2 as a simple and efficient catalyst for the hydroamination of arylacetylenes with anilines
The hydroamination reaction is a convenient alternative strategy for the formation of C– N bonds. Herein, we report a new versatile and convenient protocol for the hydroamination of arylacetylenes with anilines using palladium iodide in the absence of any added ligand as catalyst. Mild conditions, excellent regio-and stereoselectivity, and high functional group tolerance are the main features of this methodology. A subsequent reduction step gives access to a wide variety of secondary aromatic amines
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