242,481 research outputs found
Full quantum treatment of Rabi oscillation driven by a pulse train and its application in ion-trap quantum computation
Rabi oscillation of a two-level system driven by a pulse train is a basic
process involved in quantum computation. We present a full quantum treatment of
this process and show that the population inversion of this process collapses
exponentially, has no revival phenomenon, and has a dual-pulse structure in
every period. As an application, we investigate the properties of this process
in ion-trap quantum computation. We find that in the Cirac--Zoller computation
scheme, when the wavelength of the driving field is of the order m,
the lower bound of failure probability is of the order after about
controlled-NOT gates. This value is approximately equal to the
generally-accepted threshold in fault-tolerant quantum computation.Comment: 22 pages, 5 figur
Universal Correlation between Critical Temperature of Superconductivity and band structure features
The critical temperature () of superconductors varies a lot.
The factors governing the may hold key clues to understand the
nature of the superconductivity. Thereby, -involved correlations,
such as Matthias laws, Uemura law, and cuprates doping phase diagrams, have
been of great concern. However, the electronic interaction being responsible
for the carriers pairing in high- superconductors is still not
clear, which calls for more comprehensive analyses of the experimental data in
history. In this work, we propose a novel perspective for searching material
gene parameters and -involved correlations. By exploring holistic
band structure features of diverse superconductors, we found a universal
correlation between the maxima and the electron energy levels
for all kinds of superconducting materials. It suggests that the
maxima are determined by the energy level of secondary-outer orbitals, rather
than the band structure nearby the Fermi level. The energy level of
secondary-outer orbitals is a parameter corresponding to the ratio of atomic
orbital hybridization, implying that the fluctuation of the orbital
hybridization is another candidate of pairing glue
Mean-Field Limit for a Collision-Avoiding Flocking System and the Time-Asymptotic Flocking Dynamics for the Kinetic Equation
A Collision-Avoiding flocking particle system proposed in [8] is studied in
this paper. The global wellposedness of its corresponding Vlasov-type kinetic
equation is proved. As a corollary of the global stability result, the mean
field limit of the particle system is obtained. Furthermore, the
time-asymptotic flocking behavior of the solution to the kinetic equation is
also derived. The technics used for local wellposedness and stability follow
from similar ideas to those have been used in [3,22,14]. While in order to
extend the local result globally, the main contribution here is to generate a
series of new estimates for this Vlasov type equation, which imply that the
growing of the characteristics can be controlled globally. Further estimates
also show the long time flocking phenomena.Comment: 21 page
An Integrated Quadratic Reconstruction for Finite Volume Schemes to Scalar Conservation Laws in Multiple Dimensions
We proposed a piecewise quadratic reconstruction method in multiple
dimensions, which is in an integrated style, for finite volume schemes to
scalar conservation laws. This integrated quadratic reconstruction is
parameter-free and applicable on flexible grids. We show that the finite volume
schemes with the new reconstruction satisfy a local maximum principle with
properly setup on time steplength. Numerical examples are presented to show
that the proposed scheme attains a third-order accuracy for smooth solutions in
both 2D and 3D cases. It is indicated by numerical results that the local
maximum principle is helpful to prevent overshoots in numerical solutions
Solitons in Nonlinear Systems and Eigen-states in Quantum Wells
We study the relations between solitons of nonlinear Schr\"{o}dinger equation
described systems and eigen-states of linear Schr\"{o}dinger equation with some
quantum wells. Many different non-degenerated solitons are re-derived from the
eigen-states in the quantum wells. We show that the vector solitons for coupled
system with attractive interactions correspond to the identical eigen-states
with the ones of coupled systems with repulsive interactions. The energy
eigenvalues of them seem to be different, but they can be reduced to identical
ones in the same quantum wells. The non-degenerated solitons for
multi-component systems can be used to construct much abundant degenerated
solitons in more components coupled cases. On the other hand, we demonstrate
soliton solutions in nonlinear systems can be also used to solve the
eigen-problems of quantum wells. As an example, we present eigenvalue and
eigen-state in a complicated quantum well for which the Hamiltonian belongs to
the non-Hermitian Hamiltonian having Parity-Time symmetry. We further present
the ground state and the first exited state in an asymmetric quantum
double-well from asymmetric solitons. Based on these results, we expect that
many nonlinear physical systems can be used to observe the quantum states
evolution of quantum wells, such as water wave tank, nonlinear fiber,
Bose-Einstein condensate, and even plasma, although some of them are classical
physical systems. These relations provide another different way to understand
the stability of solitons in nonlinear Schr\"{o}dinger equation described
systems, in contrast to the balance between dispersion and nonlinearity.Comment: 12 pages, 3 figure
Optimized spin-injection efficiency and spin MOSFET operation based on low-barrier ferromagnet/insulator/n-Si tunnel contact
We theoretically investigate the spin injection in different FM/I/n-Si tunnel
contacts by using the lattice NEGF method. We find that the tunnel contacts
with low barrier materials such as TiO and TaO, have much lower
resistances than the conventional barrier materials, resulting in a wider and
attainable optimum parameters window for improving the spin injection
efficiency and MR ratio of a vertical spin MOSFET. Additionally, we find the
spin asymmetry coefficient of TiO tunnel contact has a negative value,
while that of TaO contact can be tuned between positive and
negative values, by changing the parameters
Optimal scheduling of isolated microgrid with an electric vehicle battery swapping station in multi-stakeholder scenarios: a bi-level programming approach via real-time pricing
In order to coordinate the scheduling problem between an isolated microgrid
(IMG) and electric vehicle battery swapping stations (BSSs) in
multi-stakeholder scenarios, a new bi-level optimal scheduling model is
proposed for promoting the participation of BSSs in regulating the IMG economic
operation. In this model, the upper-level sub-problem is formulated to minimize
the IMG net costs, while the lower-level aims to maximize the profits of the
BSS under real-time pricing environments determined by demand responses in the
upper-level decision. To solve the model, a hybrid algorithm, called JAYA-BBA,
is put forward by combining a real/integer-coded JAYA algorithm and the branch
and bound algorithm (BBA), in which the JAYA and BBA are respectively employed
to address the upper- and lower- level sub-problems, and the bi-level model is
eventually solved through alternate iterations between the two levels. The
simulation results on a microgrid test system verify the effectiveness and
superiority of the presented approach.Comment: Accepted by Applied Energ
A Two-Stage Approach for Combined Heat and Power Economic Emission Dispatch: Combining Multi-Objective Optimization with Integrated Decision Making
To address the problem of combined heat and power economic emission dispatch
(CHPEED), a two-stage approach is proposed by combining multi-objective
optimization (MOO) with integrated decision making (IDM). First, a practical
CHPEED model is built by taking into account power transmission losses and the
valve-point loading effects. To solve this model, a two-stage methodology is
thereafter proposed. The first stage of this approach relies on the use of a
powerful multi-objective evolutionary algorithm, called {\theta}-dominance
based evolutionary algorithm ({\theta}-DEA), to find multiple Pareto-optimal
solutions of the model. Through fuzzy c-means (FCM) clustering, the second
stage separates the obtained Pareto-optimal solutions into different clusters
and thereupon identifies the best compromise solutions (BCSs) by assessing the
relative projections of the solutions belonging to the same cluster using grey
relation projection (GRP). The novelty of this work is in the incorporation of
an IDM technique FCM-GRP into CHPEED to automatically determine the BCSs that
represent decision makers' different, even conflicting, preferences. The
simulation results on three test cases with varied complexity levels verify the
effectiveness and superiority of the proposed approach.Comment: Accepted by Energ
All-optical controlled phase gate in quantum dot molecules
We propose a two-qubit optically controlled phase gate in quantum dot
molecules via adiabatic passage and hole tunneling. Our proposal combines the
merits of the current generation of vertically stacked self-assembled InAs
quantum dots and adiabatic passage. The simulation shows an implementation of
the gate with a fidelity exceeding 0.98
Significant Reduction of Graphene Thermal Conductivity by Phononic Crystal Structure
We studied the thermal conductivity of graphene phononic crystal (GPnC), also
named as graphene nanomesh, by molecular dynamics simulations. The dependences
of thermal conductivity of GPnCs on both length and temperature are
investigated. It is found that the thermal conductivity of GPnCs is
significantly lower than that of graphene and can be efficiently tuned by
changing the porosity and period length. For example, the ratio of thermal
conductivity of GPnC to thermal conductivity of graphene can be changed from
0.1 to 0.01 when the porosity is changed from about 21% to 65%. The phonon
participation ratio spectra reveal that more phonon modes are localized in
GPnCs with larger porosity. Our results suggest that creating GPnCs is a
valuable method to efficiently manipulate the thermal conductivity of graphene
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