12,911 research outputs found
Implementation of controlled SWAP gates for quantum fingerprinting and photonic quantum computation
We propose a scheme to implement quantum controlled SWAP gates by directing
single-photon pulses to a two-sided cavity with a single trapped atom. The
resultant gates can be used to realize quantum fingerprinting and universal
photonic quantum computation. The performance of the scheme is characterized
under realistic experimental noise with the requirements well within the reach
of the current technology.Comment: 4 page
Topology of Knotted Optical Vortices
Optical vortices as topological objects exist ubiquitously in nature. In this
paper, by making use of the -mapping topological current theory, we
investigate the topology in the closed and knotted optical vortices. The
topological inner structure of the optical vortices are obtained, and the
linking of the knotted optical vortices is also given.Comment: 11 pages, no figures, accepted by Commun. Theor. Phys. (Beijing, P.
R. China
The application of nonlinear bistable detectors to DCT-domain watermarking schemes
Copyright 2008 Society of Photo-Optical Instrumentation Engineers. This paper was published in Complex Systems II, edited by Derek Abbott, Tomaso Aste, Murray Batchelor, Robert Dewar, Tiziana Di Matteo, Tony Guttmann, Proc. of SPIE Vol. 6802, 680215 and is made available as an electronic reprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.A DCT-domain watermarking scheme, based on nonlinear bistable detectors, is presented. A binary copyright character, i.e. watermark, is firstly reordered into a binary zig-zag sequence, and then mapped into pulse amplitude modulated waveforms. A certain desynchronization time delay can be arbitrarily placed into one code of the modulated signal, and is tolerated due to the superior robustness of nonlinear detectors over matched filters. The watermark signal is then embedded in a selected set of DCT coefficients of an image in a medium frequency range. The selected set of DCT coefficients is shuffled via the Arnold transform and looks more like background noise with respect to the watermark signal. The copyright character can be extracted by the nonlinear bistable detector without prior knowledge of the original image, i.e. blind watermark detection. Interestingly, a higher match between the original watermark character and the extracted one can be further achieved using a parallel array of bistable detectors via the mechanism of array stochastic resonance. Robustness of the proposed watermarking scheme is shown in the presence of noise, filtering, cropping and compression.Fabing Duan and Derek Abbot
Low Speed Bearing Condition Monitoring – A Case Study
The heath condition of worm-wheel gearbox is critical for the reliable and continuous operation of passenger escalators. The vibration sensor has been widely installed in the gearbox and the vibration level is usually utilized as a health indicator. However, vibration level is not robust in slow speed bearing condition monitoring. In this paper, the health condition of two slow speed bearings was evaluated using vibration data collected from sensors installed in the shaft. It has been shown that the vibration level fails to indicator the bearing health condition. The assessment accuracy can be improved by combining several simple methods
Entangling many atomic ensembles through laser manipulation
We propose an experimentally feasible scheme to generate
Greenberger-Horne-Zeilinger (GHZ) type of maximal entanglement between many
atomic ensembles based on laser manipulation and single-photon detection. The
scheme, with inherent fault tolerance to the dominant noise and efficient
scaling of the efficiency with the number of ensembles, allows to maximally
entangle many atomic ensemble within the reach of current technology. Such a
maximum entanglement of many ensembles has wide applications in demonstration
of quantum nonlocality, high-precision spectroscopy, and quantum information
processing.Comment: 4 pages, 1 figur
Non-Gaussian noise benefits for coherent detection of narrowband weak signal
Non-Gaussian noise benefits for coherent detection of narrowband weak signal
Double-maximum enhancement of signal-to-noise ratio gain via stochastic resonance and vibrational resonance
Double-maximum enhancement of signal-to-noise ratio gain via stochastic resonance and vibrational resonance
Thermalization and temperature distribution in a driven ion chain
We study thermalization and non-equilibrium dynamics in a dissipative quantum
many-body system -- a chain of ions with two points of the chain driven by
thermal bath under different temperature. Instead of a simple linear
temperature gradient as one expects from the classical heat diffusion process,
the temperature distribution in the ion chain shows surprisingly rich patterns,
which depend on the ion coupling rate to the bath, the location of the driven
ions, and the dissipation rates of the other ions in the chain. Through
simulation of the temperature evolution, we show that these unusual temperature
distribution patterns in the ion chain can be quantitatively tested in
experiments within a realistic time scale.Comment: 5 pages, 5 figure
Comment on "Quantum Phase Slips and Transport in Ultrathin Superconducting Wires"
In a recent Letter (Phys. Rev. Lett.78, 1552 (1997) ), Zaikin, Golubev, van
Otterlo, and Zimanyi criticized the phenomenological time-dependent
Ginzburg-Laudau model which I used to study the quantum phase-slippage rate for
superconducting wires. They claimed that they developed a "microscopic" model,
made qualitative improvement on my overestimate of the tunnelling barrier due
to electromagnetic field. In this comment, I want to point out that, i), ZGVZ's
result on EM barrier is expected in my paper; ii), their work is also
phenomenological; iii), their renormalization scheme is fundamentally flawed;
iv), they underestimated the barrier for ultrathin wires; v), their comparison
with experiments is incorrect.Comment: Substantial changes made. Zaikin et al's main result was expected
from my work. They underestimated tunneling barrier for ultrathin wires by
one order of magnitude in the exponen
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