1,722,164 research outputs found
Scalable scheme for entangling multiple ququarts using linear optical elements
No full textWe report a scalable linear optical scheme for generating entangled states of multiple ququarts in which the individual single-ququart state is prepared with the biphoton polarization state of frequency-nondegenerate spontaneous parametric down-conversion. The output state is calculated with the full consideration of the higher order effect (double-pair events) of spontaneous parametric down-conversion. Scalability to multiple-ququart entanglement is demonstrated with examples: linear optical entanglement of three and four individual biphoton ququarts. (C) 2007 Elsevier B.V. All rights reserved.X114sciescopu
Spectral properties of entangled photon pairs generated via frequency-degenerate type-I spontaneous parametric down-conversion
No full textWe report the complete measurement of the spectral properties of entangled photon pairs generated via frequency-degenerate type-I spontaneous parametric down-conversion pumped by a cw laser in both the collinear and the noncollinear regimes. The measurement includes the single-photon spectra as well as the two-photon joint spectra. Our results reveal interesting yet subtle differences between the collinear and the noncollinear regimes of frequency-degenerate type-I spontaneous parametric down-conversion. The single-photon and two-photon spectral measurements are in good agreement with the numerical simulation taking into account the tuning curve and the experimental geometry.open1131sciescopu
Image vector quantization using a two-stage self-organizing feature map
No full textThis paper presents a new approach to classified vector quantization in the discrete cosine transform domain (DCT/CVQ) for image compression. While most existing DCT/CVQ methods determine class features through experiences or by studying the properties of the DCT, the proposed method attempts to extract actual class features from training images utilizing a neural network model, referred to as the self-organizing feature map (SOFM). The codebook of each class is also designed using SOFM after allocating coding bits to each class with the BFOS algorithm. In the experiments using monochromatic benchmark images, the proposed approach provided 1.07 dB similar to 1.57 dB higher peak signal-to-noise ratios, (PSNRs) than the JPEG baseline system for training images at comparable bit rates. For other benchmark images, the approach improved the PSNR by up to 0.41 dB compared with the JPEG baseline system, and by up to 0.38 dB compared with an existing DCT/CVQ method that uses the Linde-Buzo-Gray (LEG) algorithm for codebook design, depending on the bit rate used.X11sciescopu
AN ELECTRICAL CHARACTERISTICS-BASED PIECEWISE-LINEAR DC MODEL OF THE MOSFET
No full textThis paper presents a new piecewise-linear de model of the MOSFET. The proposed model is derived for long channel MOSFETs from the Shichman-Hodges equations, with emphasis on the accurate modeling of the major electrical characteristics, and is extended for short channel MOSFETs. The per formance of the model is evaluated by comparing current-voltage characteristics and voltage transfer characteristics with those of the SPICE level-1 and Sakurai models. The experimental results, using three or fewer piecewise-linear region boundaries on the axes of V-GS, V-GD and V-SB, demonstrate that the proposed model provides enough accuracy for practical use with digital circuits.open11sciescopu
Atomic vapor quantum memory for a photonic polarization qubit
No full textWe report an experimental realization of an atomic vapor quantum memory for the photonic polarization qubit. The performance of the quantum memory for the polarization qubit, realized with electromagnetically-induced transparency in two spatially separated ensembles of warm Rubidium atoms in a single vapor cell, has been characterized with quantum process tomography. The process fidelity better than 0.91 for up to 16 mu s of storage time has been achieved. (c) 2010 Optical Society of AmericaX1132sciescopu
ARDOR: area optimisation algorithm for cell selection problems
No full textThe authors present a cell selection algorithm, ARDOR, which optimises the area of the cell-based design under the delay constraint. ARDOR visits a circuit in the forward direction and calculates the lower bound on the delay and area. It then binds the logic gates using the branch-and-bound formulations, while traversing the circuit in the reverse direction. Experimental results show that the ARDOR algorithm optimises the area of test circuits by 27.33% on average.X11sciescopu
Scene-Adaptive RGB-to-RGBW Conversion Using Retinex Theory-based Color Preservation
No full textThis paper proposes a retinex theory-based approach to RGB-to-RGBW conversion that preserves the human color perception within a pre-determined level of color distortion for RGBW displays. The proposed method primarily consists of two procedures. In the first, it searches for the maximum intensity level that induces no color distortion for a given image by extracting the white spectra from the common components of the RGB primary colors and adjusting all the pixels' gains uniformly. In the second, the proposed method applies an additional gain to each pixel based on its chromaticness and controls the color distortion arising from the individual gains using the color perception estimated by retinex theory and a feedback mechanism. Experimental results showed that the proposed method was more effective than conventional methods in terms of intensity increment and color preservation. For Kodak test images, the proposed method increased the average intensity by 1.4987 times with a color-distortion level of 0.0094 compared to reference RGB displays, whereas the conventional methods increased the average intensity by 0.8624-1.3429 times with color-distortion levels of 0.0325-0.0682. The surplus intensity yielded by the proposed method can be used to dynamically reduce the power consumption of a liquid crystal display (LCD) backlight or to provide brighter images on LCDs.X1110sciescopu
Efficient timing verification of latch-synchronized systems
No full textThis paper presents an event-driven approach to the timing verification of latch-synchronized systems. The proposed method performs critical path extraction and timing error detection at the same time, and extracts the critical path only if necessary By doing so, the complexity of analysis is reduced and efficiency is greatly improved over the conventional approaches which detect timing errors after extracting the complete critical paths of the system. Experimental results show that, compared to the existing methods, it provides a more than 12-fold improvement in speed on the average for ISCAS benchmark circuits, and the relative efficiency of analysis improves as the circuit size grows.open111sciescopu
State minimisation-based loop handling for critical path analysis
No full textThe authors present a new approach to the critical path analysis of digital circuits with feedback loops. The idea is to first convert a circuit with feedback loops to an equivalent minimum-sized acyclic circuit using a slate-minimisation technique of sequential machines and then to perform critical path analysis. The results of experiments illustrate that the proposed method finds critical paths correctly and efficiently in the presence of feedback loops.X11sciescopu
- …
