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71.
72.
73.
Shi-Jie Pan 《中国物理 B》2022,31(6):60304-060304
Neighborhood preserving embedding (NPE) is an important linear dimensionality reduction technique that aims at preserving the local manifold structure. NPE contains three steps, i.e., finding the nearest neighbors of each data point, constructing the weight matrix, and obtaining the transformation matrix. Liang et al. proposed a variational quantum algorithm (VQA) for NPE [Phys. Rev. A 101 032323 (2020)]. The algorithm consists of three quantum sub-algorithms, corresponding to the three steps of NPE, and was expected to have an exponential speedup on the dimensionality n. However, the algorithm has two disadvantages: (i) It is not known how to efficiently obtain the input of the third sub-algorithm from the output of the second one. (ii) Its complexity cannot be rigorously analyzed because the third sub-algorithm in it is a VQA. In this paper, we propose a complete quantum algorithm for NPE, in which we redesign the three sub-algorithms and give a rigorous complexity analysis. It is shown that our algorithm can achieve a polynomial speedup on the number of data points m and an exponential speedup on the dimensionality n under certain conditions over the classical NPE algorithm, and achieve a significant speedup compared to Liang et al.'s algorithm even without considering the complexity of the VQA. 相似文献
74.
This paper theoretically studies the double-pumped fibre-optical parametric amplifiers (FOPAs) in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the central wavelength of the two pumps. Extremely broad tuning range can be obtained when the central pump wavelength is in the normal dispersion regime and is insensitive to the wavelength separation between the two pumps, while the tuning range is narrow in the anomalous dispersion regime and can be significantly enhanced by increasing the wavelength separation. Impacts of higher-order dispersions and temporal walk-off on the gain spectra are also discussed. 相似文献
75.
76.
Anatoly S. Chirkin Mikhail Yu. Saigin Ivan V. Shutov 《Journal of Russian Laser Research》2008,29(4):336-346
We show that parametric amplification at low-frequency pumping can be implemented in aperiodic nonlinear photonic crystals.
In this process, the intensities of the waves with frequencies higher than the pumping frequency increase with increase in
the interaction length as in the case of the standard process of parametric amplification at high-frequency pumping. The process
under consideration includes a nondegenerate parametric down-conversion followed by two parametric up-conversions in the same
pumping wave. As a result, generation at four new frequencies arises. Quantum analysis of the process demonstrates the presence
of entanglement in the states of four modes.
Talk presented at the oral issue of J. Russ. Laser Res. dedicated to the memory of Professor Vladimir A. Isakov, Professor
Alexander S. Shumovsky, and Professor Andrei V. Vinogradov held in Moscow February 21–22, 2008. 相似文献
77.
文章报道了利用双通放大结构进行受激布里渊散射(SBS)脉冲压缩,实验获得了近极限压缩的脉冲,压缩率近10倍。实验中同时观察到脉冲压缩中的相位跃变。相位跃变是受激背散射光与入射激光间的增益与损耗调制的结果。 相似文献
78.
The conditions for realization of the regime of self-oscillations of the intensity of a continuously pumped solid-state laser have been qualitatively analyzed using a system of kinetic equations. It has been established that, in the case where a thin semiconductor layer absorbing light at frequencies close to the lasing frequency is placed into the cavity of such a laser, self-oscillations of its radiation intensity arise as a result of the amplitude-phase self-modulation of the laser light field.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 136–139, January–February, 2005. 相似文献
79.
Two different approaches, both exploiting two enzymes cooperative functioning, to enhance the sensitivity of tyrosinase (PPO) based biosensor for amperometric detection of phenols have been compared. For this purpose, one monoenzyme electrode (PPO) and two bienzyme electrodes (PPO and d-glucose dehydrogenase, GDH; PPO and horseradish peroxidase, HRP) were constructed using agar-agar gel as enzyme immobilization matrix. The biosensors responses for l-tyrosine detection were recorded at −50 mV versus saturated calomel electrode (SCE). The highest sensitivity (74 mA M−1) was observed for the PPO-GDH couple, while that recorded for PPO-HRP couple system was only 32 times higher than that measured for monoenzyme electrode (0.01 mA M−1). The ability of the PPO-, PPO-GDH-, PPO-HRP-based biosensors to assay phenols was demonstrated by quantitative determination of phenol, 1,2-dihydroxybenzene, 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, 2-amino-3 (4-hydroxyphenyl) propanoic acid, 2-hydroxytoluene, 3-hydroxytoluene, 4-hydroxytoluene, 4-clorophenol, 3-clorophenol, 2-clorophenol, 4-hydroxybenzoic acid. 相似文献
80.
B. Macke B. Ségard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(1):125-141
This paper deals with the apparent superluminal propagation of electromagnetic pulses in a linear dispersive medium. One specifically
examines the possibility that the pulse leaving the medium may be nearly identical to the incident one (low distortion) and
in significant advance of it (strongly negative group-delays). Favourable conditions are obtained in a dilute medium where
the required anomalous dispersion originates in an ensemble of narrow absorption or gain lines. Analytical expressions of
the advancement of the pulse centre-of-gravity and of the lowest order distortion are established from the transfer-function
of the medium. The experiments already achieved with arrangements involving a single absorption-line or a gain-doublet are
analysed in detail and compared. The considerable difficulties to overcome in order to attain advancements comparable to the
pulse width without important distortion are pointed out. New and promising schemes involving a narrow dip in a gain profile
or absorption-doublets are proposed.
Received 4 July 2002 / Received in final form 8 November 2002 Published online 4 February 2003
RID="a"
ID="a"e-mail: bruno.macke@univ-lille1.fr
RID="b"
ID="b"Unité Mixte de Recherche de l'Université et du CNRS (UMR 8523) 相似文献