3,518 research outputs found
Parallel processing for digital picture comparison
In picture processing an important problem is to identify two digital pictures of the same scene taken under different lighting conditions. This kind of problem can be found in remote sensing, satellite signal processing and the related areas. The identification can be done by transforming the gray levels so that the gray level histograms of the two pictures are closely matched. The transformation problem can be solved by using the packing method. Researchers propose a VLSI architecture consisting of m x n processing elements with extensive parallel and pipelining computation capabilities to speed up the transformation with the time complexity 0(max(m,n)), where m and n are the numbers of the gray levels of the input picture and the reference picture respectively. If using uniprocessor and a dynamic programming algorithm, the time complexity will be 0(m(3)xn). The algorithm partition problem, as an important issue in VLSI design, is discussed. Verification of the proposed architecture is also given
Coulomb Oscillations in Antidots in the Integer and Fractional Quantum Hall Regimes
We report measurements of resistance oscillations in micron-scale antidots in
both the integer and fractional quantum Hall regimes. In the integer regime, we
conclude that oscillations are of the Coulomb type from the scaling of magnetic
field period with the number of edges bound to the antidot. Based on both
gate-voltage and field periods, we find at filling factor {\nu} = 2 a tunneling
charge of e and two charged edges. Generalizing this picture to the fractional
regime, we find (again, based on field and gate-voltage periods) at {\nu} = 2/3
a tunneling charge of (2/3)e and a single charged edge.Comment: related papers at http://marcuslab.harvard.ed
Two-electron photoionization of endohedral atoms
Using as an example, we demonstrate that static potential of the
fullerene core essentially alters the cross section of the two-electron
ionization differential in one-electron energy . We found that at high photon energy prominent oscillations
appear in it due to reflection of the second, slow electron wave on the shell, which "dies out" at relatively high values, of about
23 two-electron ionization potentials. The results were presented for
ratios , where is the two-electron differential
photoionization cross section. We have calculated the ratio , that accounts for
reflection of both photoelectrons by the shell. We have calculated
also the value of two-electron photoionization cross section and found that this value is close to that of an isolated
atom.Comment: 13 pages, 4 figure
Translation-symmetry protected topological orders on lattice
In this paper we systematically study a simple class of translation-symmetry
protected topological orders in quantum spin systems using slave-particle
approach. The spin systems on square lattice are translation invariant, but may
break any other symmetries. We consider topologically ordered ground states
that do not spontaneously break any symmetry. Those states can be described by
Z2A or Z2B projective symmetry group. We find that the Z2A translation
symmetric topological orders can still be divided into 16 sub-classes
corresponding to 16 new translation-symmetry protected topological orders. We
introduced four topological indices at , , , to characterize those 16 new
topological orders. We calculated the topological degeneracies and crystal
momenta for those 16 topological phases on even-by-even, even-by-odd,
odd-by-even, and odd-by-odd lattices, which allows us to physically measure
such topological orders. We predict the appearance of gapless fermionic
excitations at the quantum phase transitions between those symmetry protected
topological orders. Our result can be generalized to any dimensions. We find
256 translation-symmetry protected Z2A topological orders for a system on 3D
lattice
A possible supersymmetric solution to the discrepancy between B -> \phi K_S and B -> \eta' K_S CP asymmetries
We present a possible supersymmetric solution to the discrepancy between the
observed mixing CP asymmetries in B -> \phi K_S and B -> \eta' K_S. We show
that due to the different parity in the final states of these processes, their
supersymmetric contributions from the R-sector have an opposite sign, which
naturally explain the large deviation between S_{\phi K_S} and S_{\eta' K_S}.
We also consider the proposed mechanisms to solve the puzzle of the observed
large branching ratio of B -> \eta' K and study their impact on S_{eta' K_S}.Comment: 4 pages, 2 figure
Topological Gauge Structure and Phase Diagram for Weakly Doped Antiferromagnets
We show that the topological gauge structure in the phase string theory of
the {\rm t-J} model gives rise to a global phase diagram of antiferromagnetic
(AF) and superconducting (SC) phases in a weakly doped regime. Dual confinement
and deconfinement of holons and spinons play essential roles here, with a
quantum critical point at a doping concentration . The complex
experimental phase diagram at low doping is well described within such a
framework.Comment: 4 pages, 2 figures, modified version, to appear in Phys. Rev. Let
Two-Dimensional Inversion Asymmetric Topological Insulators in Functionalized III-Bi Bilayers
The search for inversion asymmetric topological insulators (IATIs) persists
as an effect for realizing new topological phenomena. However, so for only a
few IATIs have been discovered and there is no IATI exhibiting a large band gap
exceeding 0.6 eV. Using first-principles calculations, we predict a series of
new IATIs in saturated Group III-Bi bilayers. We show that all these IATIs
preserve extraordinary large bulk band gaps which are well above
room-temperature, allowing for viable applications in room-temperature
spintronic devices. More importantly, most of these systems display large bulk
band gaps that far exceed 0.6 eV and, part of them even are up to ~1 eV, which
are larger than any IATIs ever reported. The nontrivial topological situation
in these systems is confirmed by the identified band inversion of the band
structures and an explicit demonstration of the topological edge states.
Interestingly, the nontrivial band order characteristics are intrinsic to most
of these materials and are not subject to spin-orbit coupling. Owning to their
asymmetric structures, remarkable Rashba spin splitting is produced in both the
valence and conduction bands of these systems. These predictions strongly
revive these new systems as excellent candidates for IATI-based novel
applications.Comment: 17 pages,5figure
Quantum simulation of artificial Abelian gauge field using nitrogen-vacancy center ensembles coupled to superconducting resonators
We propose a potentially practical scheme to simulate artificial Abelian
gauge field for polaritons using a hybrid quantum system consisting of
nitrogen-vacancy center ensembles (NVEs) and superconducting transmission line
resonators (TLR). In our case, the collective excitations of NVEs play the role
of bosonic particles, and our multiport device tends to circulate polaritons in
a behavior like a charged particle in an external magnetic field. We discuss
the possibility of identifying signatures of the Hofstadter "butterfly" in the
optical spectra of the resonators, and analyze the ground state crossover for
different gauge fields. Our work opens new perspectives in quantum simulation
of condensed matter and many-body physics using hybrid spin-ensemble circuit
quantum electrodynamics system. The experimental feasibility and challenge are
justified using currently available technology.Comment: 6 papes+supplementary materia
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