Catálogo de publicaciones - revistas

<jats:p>Rapid developments in artificial intelligence trigger demands for perception and learning of external environments through visual perception systems. Neuromorphic devices and integrated system with photosensing and response functions can be constructed to mimic complex biological visual sensing behaviors. Here, recent progresses on optoelectronic neuromorphic memristors and optoelectronic neuromorphic transistors are briefly reviewed. A variety of visual synaptic functions stimulated on optoelectronic neuromorphic devices are discussed, including light-triggered short-term plasticities, long-term plasticities, and neural facilitation. These optoelectronic neuromorphic devices can also mimic human visual perception, information processing, and cognition. The optoelectronic neuromorphic devices that simulate biological visual perception functions will have potential application prospects in areas such as bionic neurological optoelectronic systems and intelligent robots.</jats:p>

<jats:p>As a problem in data science the inverse Ising (or Potts) problem is to infer the parameters of a Gibbs–Boltzmann distributions of an Ising (or Potts) model from samples drawn from that distribution. The algorithmic and computational interest stems from the fact that this inference task cannot be carried out efficiently by the maximum likelihood criterion, since the normalizing constant of the distribution (the partition function) cannot be calculated exactly and efficiently. The practical interest on the other hand flows from several outstanding applications, of which the most well known has been predicting spatial contacts in protein structures from tables of homologous protein sequences. Most applications to date have been to data that has been produced by a dynamical process which, as far as it is known, cannot be expected to satisfy detailed balance. There is therefore no a priori reason to expect the distribution to be of the Gibbs–Boltzmann type, and no a priori reason to expect that inverse Ising (or Potts) techniques should yield useful information. In this review we discuss two types of problems where progress nevertheless can be made. We find that depending on model parameters there are phases where, in fact, the distribution is close to Gibbs–Boltzmann distribution, a non-equilibrium nature of the under-lying dynamics notwithstanding. We also discuss the relation between inferred Ising model parameters and parameters of the underlying dynamics.</jats:p>

<jats:p>Entanglement is the key resource in quantum information processing, and an entanglement witness (EW) is designed to detect whether a quantum system has any entanglement. However, prior knowledge of the target states should be known first to design a suitable EW, which weakens this method. Nevertheless, a recent theory shows that it is possible to design a universal entanglement witness (UEW) to detect negative-partial-transpose (NPT) entanglement in unknown bipartite states with measurement-device-independent (MDI) characteristic. The outcome of a UEW can also be upgraded to be an entanglement measure. In this study, we experimentally design and realize an MDI UEW for two-qubit entangled states. All of the tested states are well-detected without any prior knowledge. We also show that it is able to quantify entanglement by comparing it with concurrence estimated through state tomography. The relation between them is also revealed. The entire experimental framework ensures that the UEW is MDI.</jats:p>

<jats:p>We consider the problem of electrical properties of an <jats:italic>m</jats:italic> × <jats:italic>n</jats:italic> cylindrical network with two arbitrary boundaries, which contains multiple topological network models such as the regular cylindrical network, cobweb network, globe network, and so on. We deduce three new and concise analytical formulae of potential and equivalent resistance for the complex network of cylinders by using the RT-V method (a recursion-transform method based on node potentials). To illustrate the multiplicity of the results we give a series of special cases. Interestingly, the results obtained from the resistance formulas of cobweb network and globe network obtained are different from the results of previous studies, which indicates that our research work creates new research ideas and techniques. As a byproduct of the study, a new mathematical identity is discovered in the comparative study.</jats:p>

<jats:p>The hydrated-proton structure is critical for understanding the proton transport in water. However, whether the hydrated proton adopts Zundel or Eigen structure in solution has been highly debated in the past several decades. Current experimental techniques cannot directly visualize the dynamic structures <jats:italic>in situ</jats:italic>, while the available theoretical results on the infrared (IR) spectrum derived from current configurational models cannot fully reproduce the experimental results and thus are unable to provide their precise structures. In this work, using <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{H}}}_{5}{{\rm{O}}}_{2}^{+}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">H</mml:mi> <mml:mn>5</mml:mn> </mml:msub> <mml:msubsup> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_8_083101_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> as a model, we performed first-principles calculations to demonstrate that both the structural feature and the IR frequency of proton stretching, characteristics to discern the Zundel or Eigen structures, evolve discontinuously with the change of the O–O distance. A simple formula was introduced to discriminate the Zundel, Zundel-like, and Eigen-like structures. This work arouses new perspectives to understand the proton hydration in water.</jats:p>

<jats:p>We present the recent new developments of time-dependent Schrödinger equation and time-dependent density-functional theory for accurate and efficient treatment of the electronic structure and time-dependent quantum dynamics of many-electron atomic and molecular systems in intense laser fields. We extend time-dependent generalized pseudospectral (TDGPS) numerical method developed for time-dependent wave equations in multielectron systems. The TDGPS method allows us to obtain highly accurate time-dependent wave functions with the use of only a modest number of spatial grid point for complex quantum dynamical calculations. The usefulness of these procedures is illustrated by a few case studies of atomic and molecular processes of current interests in intense laser fields, including multiphoton ionization, above-threshold ionization, high-order harmonic generation, attosecond pulse generation, and quantum dynamical processes related to multielectron effects. We conclude this paper with some open questions and perspectives of multiphoton quantum dynamics of many-electron atomic and molecular systems in intense laser fields.</jats:p>

<jats:p>By investigating a harmonically confined and periodically driven particle system with spin–orbit coupling (SOC) and a specific controlled parameter, we demonstrate an exactly solvable two-level model with a complete set of spin-motion entangled Schrödinger kitten (or cat) states. In the undriven case, application of a modulation resonance results in the exact stationary states. We show a decoherence-averse effect of SOC and implement a transparent coherent control by exchanging positions of the probability-density wavepackets to create transitions between the different degenerate ground states. The expected energy consisting of quantum and continuous parts is derived, and the energy deviations caused by the exchange operations are much less than the quantum gap. The results could be directly extended to a weakly coupled single-particle chain for transparently encoding spin–orbit qubits via the robust spin-motion entangled degenerate ground states.</jats:p>

<jats:p>The properties of one-photon absorption (OPA), emission and two-photon absorption (TPA) of a bipyridine-based zinc ion probe are investigated employing the density functional theory in combination with response functions. The responsive mechanism and coordination mode effect are explored. The structural fluctuation is illustrated by molecular dynamics simulation. The calculated OPA and emission wavelengths of the probe are consistent with the experimental data. It is found that the red-shift of OPA wavelength and the enhancement of TPA intensity are induced by the increased intra-molecular charge transfer mechanism upon metal binding. The structural fluctuation could result in the blue-shift of TPA wavelength and the decrease of the TPA cross section. The TPA properties are quite different among the zinc complexes with different coordination modes. The TPA wavelength of the complexes with two ligands is close to that of the probe, which is in agreement with the experimental observation.</jats:p>

<jats:p>Silicene, silicon analogue to graphene which possesses a two-dimensional (2D) hexagonal lattice, has attracted increasing attention in the last few years due to predicted unique properties. However, silicon naturally possesses a three-dimensional (3D) diamond structure, so there seems to be not any natural solid phase of silicon similar to graphite. Here we report the synthesis of new silicene structure with a unique rectangular lattice by using a coherent electron beam to irradiate amorphous silicon nanofilm produced by pulsed laser deposition (PLD). Under the irradiation of coherent electron beam with proper kinetic energy, the surface layer of silicon nanofilm can be crystallized into silicene. The dynamic stability and the energy band properties of this new silicene structure are investigated by using first-principle calculations and density function theory (DFT) with the help of the observed crystalline structure and lattice constant. The new silicene structure has a real direct bandgap of 0.78 eV. Interestingly, the simulating calculation shows that the convex bond angle is 118° in the new silicene structure with rectangular lattices. The DFT simulations reveal that this new silicene structure has a Dirac-cone-like energy band. The experimental realization of silicene and the theoretically predicted properties shed light on the silicon material with potential applications in new devices.</jats:p>