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排序方式: 共有188条查询结果,搜索用时 31 毫秒
61.
We study entanglement accumulation in a memory built out of two continuous variable systems interacting with a qubit that mediates their indirect coupling. We show that, in contrast with the case of bidimensional Hilbert spaces, entanglement superior to one ebit can be accumulated in the memory, even though no entangled resource is used. The protocol is immediately implementable and we assess the role of the main imperfections. 相似文献
62.
Tame MS Prevedel R Paternostro M Böhi P Kim MS Zeilinger A 《Physical review letters》2007,98(14):140501
We report the first experimental demonstration of an all-optical one-way implementation of Deutsch's quantum algorithm on a four-qubit cluster state. All the possible configurations of a balanced or constant function acting on a two-qubit register are realized within the measurement-based model for quantum computation. The experimental results are in excellent agreement with the theoretical model, therefore demonstrating the successful performance of the algorithm. 相似文献
63.
This report concerns Lewis acid catalyzed enantioselective sulfa-Michael addition in neutral water by using a very efficient Sc(OTf)(3)/bipyridine 1 catalytic system. It is noteworthy that the protocol presented employs water as a reaction medium and allows us to obtain very high stereoselectivity and satisfactory yields for β-keto sulphides deriving from aliphatic thiols. The recovery and reuse of both the aqueous medium and the catalytic system is also reported. 相似文献
64.
Despite the weakly interacting regime, the physics of Bose–Einstein condensates is widely affected by particle–particle interactions. They determine quantum phase diffusion, which is known to be the main cause of loss of coherence. Studying a simple model of two interacting Bose systems, we show how to predict the appearance of phase diffusion beyond the Bogoliubov approximation, providing a self-consistent treatment in the framework of a generalized Hartree–Fock–Bogoliubov perturbation theory. 相似文献
65.
This contribution reports the preparation and use of a new immobilized catalyst, PS-DABCOF (9), which has been specifically designed to access for the first time the efficient β-azidation of α,β-unsaturated carboxylic acids. 相似文献
66.
Vacanti G Pugnetti S Didier N Paternostro M Palma GM Fazio R Vedral V 《Physical review letters》2012,108(9):093603
The dynamical Casimir effect (DCE) predicts the generation of photons from the vacuum due to the parametric amplification of the quantum fluctuations of an electromagnetic field. The verification of such an effect is still elusive in optical systems due to the very demanding requirements of its experimental implementation. We show that an ensemble of two-level atoms collectively coupled to the electromagnetic field of a cavity, driven at low frequencies and close to a quantum phase transition, stimulates the production of photons from the vacuum. This paves the way to an effective simulation of the DCE through a mechanism that has recently found experimental demonstration. The spectral properties of the emitted radiation reflect the critical nature of the system and allow us to link the detection of the DCE to the Kibble-Zurek mechanism for the production of defects when crossing a continuous phase transition. 相似文献
67.
Lando Mentrasti Ferdinando Cannella Mirko Pupilli Jian S. Dai 《International Journal of Solids and Structures》2013,50(20-21):3089-3096
The large bending behavior of a creased paperboard is studied in the range of rotation θ ? [0°, 180°] – new results, apparently not reported previously in literature – with the aim to point out some crucial aspect involved in an adaptive robotic manipulation of the industrial cartons.The loading tests show a great variability of the mechanical behavior, depending dramatically on the crease indentation depth (also for the specimens obtained from the same carton): (a) when the damage induced during the crease formation is relatively small, the bending response is unusually complex: the moment constitutive function, mL(θ), presents (up to) two peaks followed by unstable branches; (b) for greater indentation, the mL(θ) is monotone.In the unloading case the response mU(θ) is always monotone and is practically independent of the formation conditions of the crease. These behaviors can be easily described analytically using (piecewise) third degree splines.In a companion paper, the erection of a typical carton corner with unstable constitutive behavior is fully analyzed to detect the possible criticalities. 相似文献
68.
S. Cecchini M. Cozzi D. Di Ferdinando M. Errico F. Fabbri G. Giacomelli R. Giacomelli M. Giorgini A. Kumar J. McDonald G. Mandrioli S. Manzoor A. Margiotta E. Medinaceli L. Patrizii J. Pinfold V. Popa I. E. Qureshi O. Saavedra Z. Sahnoun G. Sirri M. Spurio V. Togo C. Valieri A. Velarde A. Zanini 《The European Physical Journal C - Particles and Fields》2008,57(3):525-533
The SLIM experiment at the Chacaltaya high altitude laboratory was sensitive to nuclearites and Q-balls which could be present
in the cosmic radiation as possible Dark Matter components. It was sensitive also to strangelets, i.e. small lumps of Strange
Quark Matter predicted at such altitudes by various phenomenological models. The analysis of 427 m2 of Nuclear Track Detectors exposed for 4.22 years showed no candidate event. New upper limits on the flux of downgoing nuclearites
and Q-balls at the 90% C.L. were established. The null result also restricts models for strangelets propagation through the
Earth atmosphere. 相似文献
69.
Dragging in Dynamical Geometry Software (DGS) is described by introducing a hierarchy of its functions. This is suitable for classifying different attitudes and aims of students who investigate a geometric problem, such as exploring, conjecturing, validating and justifying. Moreover the hierarchy has cognitive features and can be used to describe the twofold modulities namely ascending and descending in which students interact with external representations (e.g. Cabri drawings). Switching from one modality to the other through dragging often allows them to produce fruitful conjectures and to pass from the empirical to the theoretical side of the question. The genesis of such different functions in students does not happen automatically but is the consequence of specific didactical interventions of the teacher in the pupils' apprenticeship of Cabri practises. A worked-out example illustrates the theoretical concepts introduced in the paper. 相似文献
70.
Ferdinando Mancini Hideki Matsumoto Dario Villani 《Czechoslovak Journal of Physics》1996,46(4):1871-1872
Magnetic properties of the two-dimensional Hubbard model are investigated by studying the imaginary part of the dynamical spin magnetic susceptibility as a function of momentum and doping. The calculations are performed by means of the composite operator method in the static approximation. It is shown that the results are in good qualitative agreement with the experimental data for LaSrCuO compounds. 相似文献