10,914 research outputs found
Analytic Constructions of General n-Qubit Controlled Gates
In this Letter, we present two analytic expressions that most generally
simulate -qubit controlled- gates with standard one-qubit gates and CNOT
gates using exponential and polynomial complexity respectively. Explicit
circuits and general expressions of decomposition are derived. The exact
numbers of basic operations in these two schemes are given using gate counting
technique.Comment: 4 pages 7 figure
Duality and Recycling Computing in Quantum Computers
Quantum computer possesses quantum parallelism and offers great computing
power over classical computer \cite{er1,er2}. As is well-know, a moving quantum
object passing through a double-slit exhibits particle wave duality. A quantum
computer is static and lacks this duality property. The recently proposed
duality computer has exploited this particle wave duality property, and it may
offer additional computing power \cite{r1}. Simply put it, a duality computer
is a moving quantum computer passing through a double-slit. A duality computer
offers the capability to perform separate operations on the sub-waves coming
out of the different slits, in the so-called duality parallelism. Here we show
that an -dubit duality computer can be modeled by an -qubit quantum
computer. In a duality mode, computing operations are not necessarily unitary.
A -qubit quantum computer can be used as an -bit reversible classical
computer and is energy efficient. Our result further enables a -qubit
quantum computer to run classical algorithms in a -bit classical
computer. The duality mode provides a natural link between classical computing
and quantum computing. Here we also propose a recycling computing mode in which
a quantum computer will continue to compute until the result is obtained. These
two modes provide new tool for algorithm design. A search algorithm for the
unsorted database search problem is designed.Comment: 4 pages and 3 figure
Deleting a marked item from an unsorted database with a single query
In this Letter we present a quantum deletion algorithm that deletes a marked
state from an unsorted database of items with only a single query. This
algorithm achieves exponential speedup compared with classical algorithm where
O(N) number of query is required. General property of this deleting algorithm
is also studied.Comment: 4 pages and 1 figur
The reltation between the electronic structure and thermoelectric transport properties for Zintl compounds M2Zn5As4 (M=K, Rb)
The electronic structure and thermoelectric properties of are studied by the
first principles and the semiclassical BoltzTrap theory.Comment: 15page
A new transformation into State Transition Algorithm for finding the global minimum
To promote the global search ability of the original state transition
algorithm, a new operator called axesion is suggested, which aims to search
along the axes and strengthen single dimensional search. Several benchmark
minimization problems are used to illustrate the advantages of the improved
algorithm over other random search methods. The results of numerical
experiments show that the new transformation can enhance the performance of the
state transition algorithm and the new strategy is effective and reliable.Comment: 5 pages, 6 figure
Standardization, Distance, Host Galaxy Extinction of Type Ia Supernova and Hubble Diagram from the Flux Ratio Method
In this paper we generalize the flux ratio method Bailey et al. (2009) to the
case of two luminosity indicators and search the optimal luminosity-flux ratio
relations on a set of spectra whose phases are around not only the date of
bright light but also other time. With these relations, a new method is
proposed to constrain the host galaxy extinction of SN Ia and its distance. It
is first applied to the low redshift supernovas and then to the high redshift
ones. The results of the low redshift supernovas indicate that the flux ratio
method can indeed give well constraint on the host galaxy extinction parameter
E(B-V), but weaker constraints on R_{V}. The high redshift supernova spectra
are processed by the same method as the low redshift ones besides some
differences due to their high redshift. Among 16 high redshift supernovas, 15
are fitted very well except 03D1gt. Based on these distances, Hubble diagram is
drew and the contents of the Universe are analyzed. It supports an acceleration
behavior in the late Universe. Therefore, the flux ratio method can give
constraints on the host galaxy extinction and supernova distance independently.
We believe, through further studies, it may provide a precise tool to probe the
acceleration of the Universe than before.Comment: 33 pages, 9 figures and 6 table
Effects of Imperfect Gate Operations in Shor's Prime Factorization Algorithm
The effects of imperfect gate operations in implementation of Shor's prime
factorization algorithm are investigated. The gate imperfections may be
classified into three categories: the systematic error, the random error, and
the one with combined errors. It is found that Shor's algorithm is robust
against the systematic errors but is vulnerable to the random errors. Error
threshold is given to the algorithm for a given number to be factorized.Comment: 5 pages 4 figure
Meaningful Objects Segmentation from SAR Images via A Multi-Scale Non-Local Active Contour Model
The segmentation of synthetic aperture radar (SAR) images is a longstanding
yet challenging task, not only because of the presence of speckle, but also due
to the variations of surface backscattering properties in the images.
Tremendous investigations have been made to eliminate the speckle effects for
the segmentation of SAR images, while few work devotes to dealing with the
variations of backscattering coefficients in the images. In order to overcome
both the two difficulties, this paper presents a novel SAR image segmentation
method by exploiting a multi-scale active contour model based on the non-local
processing principle. More precisely, we first formulize the SAR segmentation
problem with an active contour model by integrating the non-local interactions
between pairs of patches inside and outside the segmented regions. Secondly, a
multi-scale strategy is proposed to speed up the non-local active contour
segmentation procedure and to avoid falling into local minimum for achieving
more accurate segmentation results. Experimental results on simulated and real
SAR images demonstrate the efficiency and feasibility of the proposed method:
it can not only achieve precise segmentations for images with heavy speckles
and non-local intensity variations, but also can be used for SAR images from
different types of sensors
General Phase Matching Condition for Quantum Searching
We present a general phase matching condition for the quantum search
algorithm with arbitrary unitary transformation and arbitrary phase rotations.
We show by an explicit expression that the phase matching condition depends
both on the unitary transformation U and the initial state. Assuming that the
initial amplitude distribution is an arbitrary superposition sin\theta_0 |1> +
cos\theta_0 e^{i\delta} |2> with |1> = {1 / sin\beta} \sum_k |\tau_k>
and |2> = {1 / cos\beta} \sum_{i \ne \tau}|i> , where
|\tau_k> is a marked state and \sin\beta = \sqrt{\sum_k|U_{\tau_k 0}|^2} is
determined by the matrix elements of unitary transformation U between |\tau_k>
and the |0> state, then the general phase matching condition is tan{\theta / 2}
[cos 2\beta + tan\theta_0 cos\delta sin 2\beta]= tan{\phi / 2} [1-tan\theta_0
sin\delta sin 2\beta tan{\theta / 2}], where \theta and \phi are the phase
rotation angles for |0> and |\tau_k>, respectively. This generalizes previous
conclusions in which the dependence of phase matching condition on and the
initial state has been disguised. We show that several phase conditions
previously discussed in the literature are special cases of this general one,
which clarifies the question of which condition should be regarded as exact.Comment: 8 pages, no figure
Distributed Continuous-Time and Discrete-Time Optimization With Nonuniform Unbounded Convex Constraint Sets and Nonuniform Stepsizes
This paper is devoted to distributed continuous-time and discrete-time
optimization problems with nonuniform convex constraint sets and nonuniform
stepsizes for general differentiable convex objective functions. The
communication graphs are not required to be strongly connected at any time, the
gradients of the local objective functions are not required to be bounded when
their independent variables tend to infinity, and the constraint sets are not
required to be bounded. For continuous-time multi-agent systems, a distributed
continuous algorithm is first introduced where the stepsizes and the convex
constraint sets are both nonuniform. It is shown that all agents reach a
consensus while minimizing the team objective function even when the constraint
sets are unbounded. After that, the obtained results are extended to
discrete-time multi-agent systems and then the case where each agent remains in
a corresponding convex constraint set is studied. To ensure all agents to
remain in a bounded region, a switching mechanism is introduced in the
algorithms. It is shown that the distributed optimization problems can be
solved, even though the discretization of the algorithms might deviate the
convergence of the agents from the minimum of the objective functions. Finally,
numerical examples are included to show the obtained theoretical results.Comment: 11 pages, 3figure
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