1,449 research outputs found
Single-electron latch with granular film charge leakage suppressor
A single-electron latch is a device that can be used as a building block for
Quantum-dot Cellular Automata (QCA) circuits. It consists of three nanoscale
metal "dots" connected in series by tunnel junctions; charging of the dots is
controlled by three electrostatic gates. One very important feature of a
single-electron latch is its ability to store ("latch") information represented
by the location of a single electron within the three dots. To obtain latching,
the undesired leakage of charge during the retention time must be suppressed.
Previously, to achieve this goal, multiple tunnel junctions were used to
connect the three dots. However, this method of charge leakage suppression
requires an additional compensation of the background charges affecting each
parasitic dot in the array of junctions. We report a single-electron latch
where a granular metal film is used to fabricate the middle dot in the latch
which concurrently acts as a charge leakage suppressor. This latch has no
parasitic dots, therefore the background charge compensation procedure is
greatly simplified. We discuss the origins of charge leakage suppression and
possible applications of granular metal dots for various single-electron
circuits.Comment: 21 pages, 4 figure
Stability of Landau-Ginzburg branes
We evaluate the ideas of Pi-stability at the Landau-Ginzburg point in moduli
space of compact Calabi-Yau manifolds, using matrix factorizations to B-model
the topological D-brane category. The standard requirement of unitarity at the
IR fixed point is argued to lead to a notion of "R-stability" for matrix
factorizations of quasi-homogeneous LG potentials. The D0-brane on the quintic
at the Landau-Ginzburg point is not obviously unstable. Aiming to relate
R-stability to a moduli space problem, we then study the action of the gauge
group of similarity transformations on matrix factorizations. We define a naive
moment map-like flow on the gauge orbits and use it to study boundary flows in
several examples. Gauge transformations of non-zero degree play an interesting
role for brane-antibrane annihilation. We also give a careful exposition of the
grading of the Landau-Ginzburg category of B-branes, and prove an index theorem
for matrix factorizations.Comment: 46 pages, LaTeX, summary adde
Equivalences between GIT quotients of Landau-Ginzburg B-models
We define the category of B-branes in a (not necessarily affine)
Landau-Ginzburg B-model, incorporating the notion of R-charge. Our definition
is a direct generalization of the category of perfect complexes. We then
consider pairs of Landau-Ginzburg B-models that arise as different GIT
quotients of a vector space by a one-dimensional torus, and show that for each
such pair the two categories of B-branes are quasi-equivalent. In fact we
produce a whole set of quasi-equivalences indexed by the integers, and show
that the resulting auto-equivalences are all spherical twists.Comment: v3: Added two references. Final version, to appear in Comm. Math.
Phy
Defect detection in nano-scale transistors based on radio-frequency reflectometry
Radio-frequency reflectometry in silicon single-electron transistors (SETs)
is presented. At low temperatures (<4 K), in addition to the expected Coulomb
blockade features associated with charging of the SET dot, quasi-periodic
oscillations are observed that persist in the fully depleted regime where the
SET dot is completely empty. A model, confirmed by simulations, indicates that
these oscillations originate from charging of an unintended floating gate
located in the heavily doped polycrystalline silicon gate stack. The technique
used in this experiment can be applied for detailed spectroscopy of various
charge defects in nanoscale SETs and field effect transistorsComment: 3 pages, 3 figure
Quantum dynamics, dissipation, and asymmetry effects in quantum dot arrays
We study the role of dissipation and structural defects on the time evolution
of quantum dot arrays with mobile charges under external driving fields. These
structures, proposed as quantum dot cellular automata, exhibit interesting
quantum dynamics which we describe in terms of equations of motion for the
density matrix. Using an open system approach, we study the role of asymmetries
and the microscopic electron-phonon interaction on the general dynamical
behavior of the charge distribution (polarization) of such systems. We find
that the system response to the driving field is improved at low temperatures
(and/or weak phonon coupling), before deteriorating as temperature and
asymmetry increase. In addition to the study of the time evolution of
polarization, we explore the linear entropy of the system in order to gain
further insights into the competition between coherent evolution and
dissipative processes.Comment: 11pages,9 figures(eps), submitted to PR
Representations for Three-Body T-Matrix on Unphysical Sheets: Proofs
A proof is given for the explicit representations which have been formulated
in the author's previous work (nucl-th/9505028) for the Faddeev components of
three-body T-matrix continued analytically on unphysical sheets of the energy
Riemann surface. Also, the analogous representations for analytical
continuation of the three-body scattering matrices and resolvent are proved. An
algorithm to search for the three-body resonances on the base of the Faddeev
differential equations is discussed.Comment: 98 Kb; LaTeX; Journal-ref was added (the title changed in the
journal
Representations for Three-Body T-Matrix on Unphysical Sheets
Explicit representations are formulated for the Faddeev components of
three-body T-matrix continued analytically on unphysical sheets of the energy
Riemann surface. According to the representations, the T-matrix on unphysical
sheets is obviously expressed in terms of its components taken on the physical
sheet only. The representations for T-matrix are used then to construct similar
representations for analytical continuation of three-body scattering matrices
and resolvent. Domains on unphysical sheets are described where the
representations obtained can be applied.Comment: 123 Kb; LaTeX; Journal-ref was added (the title changed in the
journal
Concentration and power dependences of level population of 2.8-mu m laser transition in YLF : Er crystals under CW laser diode pumping
An influence of interionic cross relaxation processes (upconversion, selfquenching) on concentration and power dependences of the inverse population of ^4I_(11/2) and ^4I_(13/2) laser levels in YLF:Er crystals under CW laser-diode pumping were studied both theoretically and experimentally. Computer simulations were carried out taking into account not only pair interaction but also the multi-ion interaction in the whole system. Optimal Er concentration for 3 - µm CW lasing was estimated as 10 - 15%
Cellular Structures for Computation in the Quantum Regime
We present a new cellular data processing scheme, a hybrid of existing
cellular automata (CA) and gate array architectures, which is optimized for
realization at the quantum scale. For conventional computing, the CA-like
external clocking avoids the time-scale problems associated with ground-state
relaxation schemes. For quantum computing, the architecture constitutes a novel
paradigm whereby the algorithm is embedded in spatial, as opposed to temporal,
structure. The architecture can be exploited to produce highly efficient
algorithms: for example, a list of length N can be searched in time of order
cube root N.Comment: 11 pages (LaTeX), 3 figure
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