37,260 research outputs found
Grover Algorithm with zero theoretical failure rate
In standard Grover's algorithm for quantum searching, the probability of
finding the marked item is not exactly 1. In this Letter we present a modified
version of Grover's algorithm that searches a marked state with full successful
rate. The modification is done by replacing the phase inversion by two phase
rotation through angle . The rotation angle is given analytically to be
, where
, the number of items in the database, and
an integer equal to or greater than the integer part of . Upon measurement at -th iteration, the marked state
is obtained with certainty.Comment: 5 pages. Accepted for publication in Physical Review
The interpretation of the field angle dependence of the critical current in defect-engineered superconductors
We apply the vortex path model of critical currents to a comprehensive
analysis of contemporary data on defect-engineered superconductors, showing
that it provides a consistent and detailed interpretation of the experimental
data for a diverse range of materials. We address the question of whether
electron mass anisotropy plays a role of any consequence in determining the
form of this data and conclude that it does not. By abandoning this false
interpretation of the data, we are able to make significant progress in
understanding the real origin of the observed behavior. In particular, we are
able to explain a number of common features in the data including shoulders at
intermediate angles, a uniform response over a wide angular range and the
greater discrimination between individual defect populations at higher fields.
We also correct several misconceptions including the idea that a peak in the
angular dependence of the critical current is a necessary signature of strong
correlated pinning, and conversely that the existence of such a peak implies
the existence of correlated pinning aligned to the particular direction. The
consistency of the vortex path model with the principle of maximum entropy is
introduced.Comment: 14 pages, 7 figure
Spurious Shell Closures in the Relativistic Mean Field Model
Following a systematic theoretical study of the ground-state properties of
over 7000 nuclei from the proton drip line to the neutron drip line in the
relativistic mean field model [Prog. Theor. Phys. 113 (2005) 785], which is in
fair agreement with existing experimental data, we observe a few spurious shell
closures, i.e. proton shell closures at Z=58 and Z=92. These spurious shell
closures are found to persist in all the effective forces of the relativistic
mean field model, e.g. TMA, NL3, PKDD and DD-ME2.Comment: 3 pages, to appear in Chinese Physics Letter
Rare Kaon Decay K^+ --> \pi^+ \nu \bar{\nu} in SU(3)_C X SU(3)_L X U(1)_N Models
The rare kaon decay K^+ --> \pi^+ \nu \bar{\nu} is considered in the
framework of the models based on the SU(3)_C X SU(3)_L X U(1)_N (3 - 3 - 1)
gauge group. It is shown that a lower bound of the Z' mass in the 3 - 3 - 1
model with right-handed neutrinos at a value of 3 TeV is derived, while that in
the minimal version -- 1.7 TeV.Comment: 7 pages, 1 figure, late
Long-range Casimir interactions between impurities in nematic liquid crystals and the collapse of polymer chains in such solvents
The elastic interactions between objects embedded in a nematic liquid crystal
are usually caused by the average distorsion-rather than by the fluctuations-of
the nematic orientational field. We argue that for sufficiently small
particles, the nematic-mediated interaction originates purely from the
fluctuations of the nematic director. This Casimir interaction decays as
d^(-6), d being the distance between the particles, and it dominates van der
Waals interactions close to the isotropic-to-nematic transition. Considering
the nematic as a polymer solvent, we show that the onset of this Casimir
interaction at the isotropic-to-nematic transition can discontinuously induce
the collapse of a flexible polymer chain from the swollen state to the globular
state, without crossing the Theta-point.Comment: 6 pages, 1 figur
The Precise Formula in a Sine Function Form of the norm of the Amplitude and the Necessary and Sufficient Phase Condition for Any Quantum Algorithm with Arbitrary Phase Rotations
In this paper we derived the precise formula in a sine function form of the
norm of the amplitude in the desired state, and by means of he precise formula
we presented the necessary and sufficient phase condition for any quantum
algorithm with arbitrary phase rotations. We also showed that the phase
condition: identical rotation angles, is a sufficient but not a necessary phase
condition.Comment: 16 pages. Modified some English sentences and some proofs. Removed a
table. Corrected the formula for kol on page 10. No figure
Exact Quantum Search by Parallel Unitary Discrimination Schemes
We study the unsorted database search problem with items from the
viewpoint of unitary discrimination. Instead of considering the famous
Grover's the bounded-error algorithm for the original problem, we
seek for the results about the exact algorithms, i.e. the ones succeed with
certainty. Under the standard oracle model , we demonstrate a tight lower bound of the number of queries
for any parallel scheme with unentangled input states. With the assistance of
entanglement, we obtain a general lower bound . We provide
concrete examples to illustrate our results. In particular, we show that the
case of N=6 can be solved exactly with only two queries by using a bipartite
entangled input state. Our results indicate that in the standard oracle model
the complexity of exact quantum search with one unique solution can be strictly
less than that of the calculation of OR function.Comment: 8 pages (revtex4), 6 figures. Revised version with some typo error
corrections and some clearer statement. Accepted by Phys.Rev.A .Comments are
welcome
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