1,551 research outputs found
Experimental Quantum Cryptography with Qutrits
We produce two identical keys using, for the first time, entangled trinary
quantum systems (qutrits) for quantum key distribution. The advantage of
qutrits over the normally used binary quantum systems is an increased coding
density and a higher security margin. The qutrits are encoded into the orbital
angular momentum of photons, namely Laguerre-Gaussian modes with azimuthal
index l +1, 0 and -1, respectively. The orbital angular momentum is controlled
with phase holograms. In an Ekert-type protocol the violation of a
three-dimensional Bell inequality verifies the security of the generated keys.
A key is obtained with a qutrit error rate of approximately 10 %.Comment: New version includes additional references and a few minor changes to
the manuscrip
Suppression of the imprinted gene NNAT and X-Chromosome gene activation in isogenic human iPS cells
Genetic comparison between human embryonic stem cells and induced pluripotent stem cells has been hampered by genetic variation. To solve this problem, we have developed an isogenic system that allows direct comparison of induced pluripotent stem cells (hiPSCs) to their genetically matched human embryonic stem cells (hESCs). We show that hiPSCs have a highly similar transcriptome to hESCs. Global transcriptional profiling identified 102-154 genes (\u3e2 fold) that showed a difference between isogenic hiPSCs and hESCs. A stringent analysis identified NNAT as a key imprinted gene that was dysregulated in hiPSCs. Furthermore, a disproportionate number of X-chromosome localized genes were over-expressed in female hiPSCs. Our results indicate that despite a remarkably close transcriptome to hESCs, isogenic hiPSCs have alterations in imprinting and regulation of X-chromosome genes. © 2011 Teichroeb et al
Robust Multi-Partite Multi-Level Quantum Protocols
We present a tripartite three-level state that allows a secret sharing
protocol among the three parties, or a quantum key distribution protocol
between any two parties. The state used in this scheme contains entanglement
even after one system is traced out. We show how to utilize this residual
entanglement for quantum key distribution purposes, and propose a realization
of the scheme using entanglement of orbital angular momentum states of photons.Comment: 9 pages, 2 figure
Facies analysis and paleoenvironmental reconstruction of Upper Cretaceous sequences in the eastern Para-Tethys Basin, NW Iran
Upper Cretaceous mixed carbonate-siliciclastic sequences are among the most important targets for hydrocarbon exploration in the Moghan area, located in the eastern Para-Tethys Basin. Despite of their significance, little is known about their facies characteristics and depositional environments. Detailed facies analysis and paleoenvironmental reconstruction of these sequences have been carried out in eight surface sections. Accordingly, four siliciclastic facies, eight carbonate facies and one volcanic facies have been recognized. Detailed facies descriptions and interpretations, together with the results of facies frequency analysis, standard facies models and Upper Cretaceous depositional models of Para-Tethys Basin, have been integrated and a non-rimmed carbonate platform is presented. This platform was affected by siliciclastic influx, in the form of coastal fan delta and submarine fans in the shallow- to deep-marine parts, respectively. This model is interpreted to be shallower in the central and northeastern parts of the Moghan area. Toward the southeast and southwest, this shallow platform turns into deep marine settings along steep slopes without remarkable marginal barriers
Analysis of the Brinkman-Forchheimer equations with slip boundary conditions
In this work, we study the Brinkman-Forchheimer equations driven under slip
boundary conditions of friction type. We prove the existence and uniqueness of
weak solutions by means of regularization combined with the Faedo-Galerkin
approach. Next we discuss the continuity of the solution with respect to
Brinkman's and Forchheimer's coefficients. Finally, we show that the weak
solution of the corresponding stationary problem is stable
Persistence of a pinch in a pipe
The response of low-dimensional solid objects combines geometry and physics
in unusual ways, exemplified in structures of great utility such as a
thin-walled tube that is ubiquitous in nature and technology. Here we provide a
particularly surprising consequence of this confluence of geometry and physics
in tubular structures: the anomalously large persistence of a localized pinch
in an elastic pipe whose effect decays very slowly as an oscillatory
exponential with a persistence length that diverges as the thickness of the
tube vanishes, which we confirm experimentally. The result is more a
consequence of geometry than material properties, and is thus equally
applicable to carbon nanotubes as it is to oil pipelines.Comment: 6 pages, 3 figure
Optical vernier technique for in-situ measurement of the length of long Fabry-Perot cavities
We propose a method for in-situ measurement of the length of kilometer size
Fabry-Perot cavities in laser gravitational wave detectors. The method is based
on the vernier, which occurs naturally when the laser incident on the cavity
has a sideband. By changing the length of the cavity over several wavelengths
we obtain a set of carrier resonances alternating with sideband resonances.
From the measurement of the separation between the carrier and a sideband
resonance we determine the length of the cavity. We apply the technique to the
measurement of the length of a Fabry-Perot cavity in the Caltech 40m
Interferometer and discuss the accuracy of the technique.Comment: LaTeX 2e, 12 pages, 4 figure
Experimental Quantum Coin Tossing
In this letter we present the first implementation of a quantum coin tossing
protocol. This protocol belongs to a class of ``two-party'' cryptographic
problems, where the communication partners distrust each other. As with a
number of such two-party protocols, the best implementation of the quantum coin
tossing requires qutrits. In this way, we have also performed the first
complete quantum communication protocol with qutrits. In our experiment the two
partners succeeded to remotely toss a row of coins using photons entangled in
the orbital angular momentum. We also show the experimental bounds of a
possible cheater and the ways of detecting him
Curvature condensation and bifurcation in an elastic shell
We study the formation and evolution of localized geometrical defects in an
indented cylindrical elastic shell using a combination of experiment and
numerical simulation. We find that as a symmetric localized indentation on a
semi-cylindrical shell increases, there is a transition from a global mode of
deformation to a localized one which leads to the condensation of curvature
along a symmetric parabolic crease. This process introduces a soft mode in the
system, converting a load-bearing structure into a hinged, kinematic mechanism.
Further indentation leads to twinning wherein the parabolic crease bifurcates
into two creases that move apart on either side of the line of symmetry. A
qualitative theory captures the main features of the phenomena and leads to
sharper questions about the nucleation of these defects.Comment: 4 pages, 5 figures, submitted to Physical Review Letter
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