2,099 research outputs found
One-step preparation of cluster states in quantum dot molecules
Cluster states, a special type of highly entangled states, are a universal
resource for measurement-based quantum computation. Here, we propose an
efficient one-step generation scheme for cluster states in semiconductor
quantum dot molecules, where qubits are encoded on singlet and triplet state of
two coupled quantum dots. By applying a collective electrical field or
simultaneously adjusting interdot bias voltages of all double-dot molecule, we
get a switchable Ising-like interaction between any two adjacent quantum
molecule qubits. The initialization, the single qubit measurement, and the
experimental parameters are discussed, which shows the large cluster state
preparation and one-way quantum computation implementable in semiconductor
quantum dots with the present techniques.Comment: 5 pages, 3 figure
Low energy exciton states in a nanoscopic semiconducting ring
We consider an effective mass model for an electron-hole pair in a simplified
confinement potential, which is applicable to both a nanoscopic self-assembled
semiconducting InAs ring and a quantum dot. The linear optical susceptibility,
proportional to the absorption intensity of near-infrared transmission, is
calculated as a function of the ring radius . Compared with the
properties of the quantum dot corresponding to the model with a very small
radius , our results are in qualitative agreement with the recent
experimental measurements by Pettersson {\it et al}.Comment: 4 pages, 4 figures, revised and accepted by Phys. Rev.
Solid reconstruction using recognition of quadric surfaces from orthographic views
International audienceThe reconstruction of 3D objects from 2D orthographic views is crucial for maintaining and further developing existing product designs. A B-rep oriented method for reconstructing curved objects from three orthographic views is presented by employing a hybrid wire-frame in place of an intermediate wire-frame. The Link-Relation Graph (LRG) is introduced as a multi-graph representation of orthographic views, and quadric surface features (QSFs) are defined by special basic patterns of LRG as well as aggregation rules. By hint-based pattern matching in the LRGs of three orthographic views in an order of priority, the corresponding QSFs are recognized, and the geometry and topology of quadric surfaces are recovered simultaneously. This method can handle objects with interacting quadric surfaces and avoids the combinatorial search for tracing all the quadric surfaces in an intermediate wire-frame by the existing methods. Several examples are provided
Converting Hybrid Wire-frames to B-rep Models
International audienceSolid reconstruction from engineering drawings is one of the efficient technologies to product solid models. The B-rep oriented approach provides a practical way for reconstructing a wide range of objects. However, its major limitation is the computational complexity involved in the search for all valid faces from the intermediate wire-frame, especially for objects with complicated face topologies. In previous work, we presented a hint-based algorithm to recognize quadric surfaces from orthographic views and generate a hybrid wire-frame as the intermediate model of our B-rep oriented method. As a key stage in the process of solid reconstructing, we propose an algorithm to convert the hybrid wire-frame to the final B-rep model by extracting all the rest faces of planes based on graph theory. The entities lying on the same planar surface are first collected in a plane graph. After all the cycles are traced in a simplified edge-adjacency matrix of the graph, the face loops of the plane are formed by testing loop containment and assigning loop directions. Finally, the B-rep model is constructed by sewing all the plane faces based on the M¨obius rule. The method can efficiently construct 2- manifold objects with a variety of face topologies, which is illustrated by results of implementatio
Mesoscopic Kondo screening effect in a single-electron transistor embedded in a metallic ring
We study the Kondo screening effect generated by a single-electron transistor
or quantum dot embedded in a small metallic ring. When the ring circumference
becomes comparable to the fundamental length scale associated with the {\it bulk} Kondo tempe the Kondo resonance is
strongly affected, depending on the total number of electrons ({\it modulo} 4)
and magnetic flux threading the ring. The resulting Kondo-assisted persistent
currents are also calculated in both Kondo and mixed valence regimes, and the
maximum values are found in the crossover region.Comment: 4 pages, Revtex, 6 figures, more references are include
Valence bond spin liquid state in two-dimensional frustrated spin-1/2 Heisenberg antiferromagnets
Fermionic valence bond approach in terms of SU(4) representation is proposed
to describe the frustrated Heisenberg antiferromagnetic (AF)
model on a {\it bipartite} square lattice. A uniform mean field solution
without breaking the translational and rotational symmetries describes a
valence bond spin liquid state, interpolating the two different AF ordered
states in the large and large limits, respectively. This novel
spin liquid state is gapless with the vanishing density of states at the Fermi
nodal points. Moreover, a sharp resonance peak in the dynamic structure factor
is predicted for momenta and in the strongly
frustrated limit , which can be checked by neutron
scattering experiment.Comment: Revtex file, 4 pages, 4 figure
Miniaturization of Branch-Line Coupler Using Composite Right/Left-Handed Transmission Lines with Novel Meander-shaped-slots CSSRR
A novel compact-size branch-line coupler using composite right/left-handed transmission lines is proposed in this paper. In order to obtain miniaturization, composite right/left-handed transmission lines with novel complementary split single ring resonators which are realized by loading a pair of meander-shaped-slots in the split of the ring are designed. This novel coupler occupies only 22.8% of the area of the conventional approach at 0.7 GHz. The proposed coupler can be implemented by using the standard printed-circuit-board etching processes without any implementation of lumped elements and via-holes, making it very useful for wireless communication systems. The agreement between measured and stimulated results validates the feasible configuration of the proposed coupler
Unusual Compression Behavior of Columbite TiO2 via First-Principles Calculations
The physical mechanisms behind the reduction of the bulk modulus of a
high-pressure cubic TiO2 phase are confirmed by first-principles calculations.
An unusual and abrupt change occurs in the dependence of energy on pressure at
43 GPa, indicating a pressure-induced phase transition from columbite TiO2 to a
newly-identified modified fluorite TiO2 with a Pca21 symmetry. Oxygen atom
displacement in Pca21 TiO2 unexpectedly reduces the bulk modulus by 34%
relative to fluorite TiO2. This discovering provides a direct evidence for
understanding the compressive properties of such groups of homologous materialsComment: [email protected] or [email protected]
Dispersive Coupling Between the Superconducting Transmission Line Resonator and the Double Quantum Dots
Realization of controllable interaction between distant qubits is one of the
major problems in scalable solid state quantum computing. We study a
superconducting transmission line resonator (TLR) as a tunable dispersive
coupler for the double-dot molecules. A general interaction Hamiltonian of
two-electron spin-based qubits and the TLR is presented, where the double-dot
qubits are biased at the large detuning region and the TLR is always empty and
virtually excited. Our analysis o the main decoherence sources indicates that
various major quantum operations can be reliably implemented with current
technology.Comment: 10 pages, 5 figure
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