1,319 research outputs found
Quantum noise in optical interferometers
We study the photon counting noise in optical interferometers used for
gravitational wave detection. In order to reduce quantum noise a squeezed
vacuum is injected into the usually unused input port. It is investigated under
which conditions the gravitational wave signal may be amplified without
increasing counting noise concurrently. Such a possibility was suggested as a
consequence of the entanglement of the two output ports of a beam splitter. We
find that amplification without concurrent increase of noise is not possible
for reasonable squeezing parameters. Photon distributions for various beam
splitter angles and squeezing parameters are calculated.Comment: 15 pages, 7 figure
Cohomology of Conformal Algebras
Conformal algebra is an axiomatic description of the operator product
expansion of chiral fields in conformal field theory. On the other hand, it is
an adequate tool for the study of infinite-dimensional Lie algebras satisfying
the locality property. The main examples of such Lie algebras are those
``based'' on the punctured complex plane, like the Virasoro algebra and loop
algebras. In the present paper we develop a cohomology theory of conformal
algebras with coefficients in an arbitrary module. It possesses standard
properties of cohomology theories; for example, it describes extensions and
deformations. We offer explicit computations for most of the important
examples.Comment: 46 pp., AMSLaTeX, uses epsfig, amssymb, amsc
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
Q-phonon description of low lying 1^- two-phonon states in spherical nuclei
The properties of 1^-_1 two-phonon states and the characteristics of E1
transition probabilities between low-lying collective states in spherical
nuclei are analysed within the Q-phonon approach to the description of
collective states. Several relations between observables are obtained.
Microscopic calculations of the E1 0^+_1 -> 1^-_1 transition matrix elements
are performed on the basis of the RPA. A satisfactory description of the
experimental data is obtained.Comment: 16 pages, 2 figures, 9 table
On Weyl Quantization from geometric Quantization
A. Weinstein has conjectured a nice looking formula for a deformed product of
functions on a hermitian symmetric space of non-compact type. We derive such a
formula for symmetric symplectic spaces using ideas from geometric quantization
and prequantization of symplectic groupoids. We compute the result explicitly
for the natural 2-dimensional symplectic manifolds: the euclidean plane, the
sphere and the hyperbolic plane. For the euclidean plane we obtain the well
known Moyal-Weyl product. The other cases show that Weinstein's original idea
should be interpreted with care. We conclude with comments on the status of our
result.Comment: 11 pages. (v2: corrected a couple of typos
Quantum correlations of twophoton polarization states in the parametric down-conversion process
We consider correlation properties of twophoton polarization states in the
parametric down-conversion process. In our description of polarization states
we take into account the simultaneous presence of colored and white noise in
the density matrix. Within the considered model we study the dependence of the
von Neumann entropy on the noise amount in the system and derive the
separability condition for the density matrix of twophoton polarization state,
using Perec-Horodecki criterion and majorization criterion. Then the dependence
of the Bell operator (in CHSH form) on noise is studied. As a result, we give a
condition for determining the presence of quantum correlation states in
experimental measurements of the Bell operator. Finally, we compare our
calculations with experimental data [doi:10.1103/PhysRevA.73.062110] and give a
noise amount estimation in the photon polarization state considered there.Comment: 10 pages, 7 figures; corrected typo
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
How to turn a brand's friends (and detractors) into evangelists: The case of Canadian wine
With conversion rituals, cool-climate wineries in Ontario managed to overcome a reputation for low quality, write Felipe G. Massa, Wesley Helms, Maxim Voronov and Liang Wan
Digital twins in logistics
The logistics industry has undergone significant transformation over the years, thanks to advancements in technology. One of the most promising technologies disrupting the industry is digital twins. In this article, we explore the concept of digital twins in logistics, their benefits, and their potential impact on the industry
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