7,026 research outputs found
Anticorrelation effect in femtosecond-pulse pumped type-II spontaneous parametric down-conversion
No full textWe report an experimental demonstration of an anticorrelation effect in femtosecond-pulse pumped type-II spontaneous parametric down-conversion. Our experimental data, which is different from that of Atature et al. [Phys. Rev. Lett. 83, 1323 (2000)], confirmed the shallow symmetric "dip" that is predicted theoretically by Keller and Rubin [Phys. Rev. A 56, 1534 (1997)] and Grice and Walmsley [Phys. Rev. A 56, 1627 (1997)]. We show in this paper that the asymmetric dip observed in the literature is an artifact, which is caused by the asymmetric optical elements introduced into the beam path after the down-conversion process. The "partial distinguishability" theory suggested by Atature et al. is therefore incorrect
Two-photon correlation of chaotic light: A quantum interference phenomenon
No full textTwo-photon correlation phenomena of chaotic light, including the historical Hanbury Brown and Twiss effect, are essentially the quantum effect of two-photon interference, instead of the classical statistical correlation between intensity fluctuations. To support our view, we analyze a "ghost" imaging experiment with chaotic light for which the classical understanding does not give a satisfactory interpretation. We also provide a two-photon optical picture of ghost imaging with chaotic light in terms of a two-photon phase-conjugate mirror, which suggests lensless imaging applications for radiations for which no effective lens is available
Fast Inter-Frame Coding with Intra Skip Strategy in H.264 Video Coding
No full text[[abstract]]Inter-frame coding in the H.2641AVC standard must address inter modes and intra modes when seeking the best coding mode. Despite achieving a higher coding efficiency than any other previous coding standards, H.2641AVC also has a significantly high computation complexity. This investigation, based on the information of the histogram difference and rate part of the rate-distortion optimization in motion estimation, develops at? algorithm using fuzzy logic to achieve high coding efficiency and decrease the computation complexity. The histogram difference is utilized to measure the similarity of two adjacent frames. The rate part of rate-distortion optimization ensures a very low bit rate of the encoded bits. Fuzzy logic is then employed to determine whether the intra coding mode can be skipped in inter-frame coding to reduce the encoding time. Experimental results demonstrate that the proposed algorithm reduces the encoding time by tip to 32%, while maintaining the same quality and slightly increasing the bit rate.(1)[[note]]SC
Stable organic blue-light-emitting devices prepared from poly[spiro(fluorene-9,9’-xanthene)]
No full textFACTORIZATION OF INTEGERS WITH MULTI-PATH OPTICAL INTERFERENCE
No full textWe introduce a new factorization algorithm based on the optical computation by multi-path interference of the periodicity of a "factoring" function given by exponential sums at continuous arguments. We demonstrate that this algorithm allows, in principle, the prime number decomposition of several large numbers by exploiting a remarking rescaling property of this periodic function. Such a function is recorded by measuring optical interferograms with a multi-path Michelson interferometer, a polychromatic light source and a spectrometer. The information about factors is encoded in the location of the inteferogram maxima
Temporal indistinguishability and quantum interference
No full textA chi((2)) nonlinear optical crystal is pumped by two temporally well-distinguishable femtosecond laser pulses to generate entangled photon pairs in the process of spontaneous parametric down-conversion. We have observed first- and second-order interference between amplitudes generated from the first and the second pump pulse as a function of the time delay between the two pump pulses. The criteria for first- and second-order interference are found to be very different, which reflect the quantum entanglement nature of the state of spontaneous parametric down-conversion
New factorization algorithm based on a continuous representation of truncated Gauss sums
No full textIn this paper, we will describe a new factorization algorithm based on the continuous representation of Gauss sums, generalizable to orders j > 2. Such an algorithm allows one, for the first time, to find all the factors of a number N in a single run without precalculating the ratio N/l, where l are all the possible trial factors. Continuous truncated exponential sums turn out to be a powerful tool for distinguishing factors from non-factors (we also suggest, with regard to this topic, to read an interesting paper by S. Wölk et al. also published in this issue [Wölk, Feiler, Schleich, J. Mod. Opt. in press]) and factorizing different numbers at the same time. We will also describe two possible M-path optical interferometers, which can be used to experimentally realize this algorithm: a liquid crystal grating and a generalized symmetric Michelson interferometer
Factorization algorithm based on the periodicity measurement of a CTES
No full textWe introduce a new factorization algorithm based on the measurement of the periodicity of a determined function, similar to Shor's algorithm. In particular, such a function is given by a generalized continuous truncated exponential sum (CTES). The CTES interference pattern satisfies a remarkable scaling property, which allows one to plot the interferogram as a function of a suitable continuous variable depending on the number to factorize. This allows one, in principle, to factorize arbitrary numbers with a single interferogram. In particular, information about the factors is encoded in the location of the interference maxima, which repeat periodically in the interferogram. A possible analogue computer for the implementation of such an algorithm can be realized using multi-path optical interferometers, with polychromatic light sources and a high-resolution spectrometer. The experimental accuracy in the realization of the CTES interferogram and the bandwidth of the polychromatic sources determine the largest number Nmax factorable. Once the CTES interferogram is recorded, all the numbers with value up to Nmax can be factorable, without performing any further measurement
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