1,269 research outputs found
The quantum speed up as advanced knowledge of the solution
With reference to a search in a database of size N, Grover states: "What is
the reason that one would expect that a quantum mechanical scheme could
accomplish the search in O(square root of N) steps? It would be insightful to
have a simple two line argument for this without having to describe the details
of the search algorithm". The answer provided in this work is: "because any
quantum algorithm takes the time taken by a classical algorithm that knows in
advance 50% of the information that specifies the solution of the problem".
This empirical fact, unnoticed so far, holds for both quadratic and exponential
speed ups and is theoretically justified in three steps: (i) once the physical
representation is extended to the production of the problem on the part of the
oracle and to the final measurement of the computer register, quantum
computation is reduction on the solution of the problem under a relation
representing problem-solution interdependence, (ii) the speed up is explained
by a simple consideration of time symmetry, it is the gain of information about
the solution due to backdating, to before running the algorithm, a
time-symmetric part of the reduction on the solution; this advanced knowledge
of the solution reduces the size of the solution space to be explored by the
algorithm, (iii) if I is the information acquired by measuring the content of
the computer register at the end of the algorithm, the quantum algorithm takes
the time taken by a classical algorithm that knows in advance 50% of I, which
brings us to the initial statement.Comment: 23 pages, to be published in IJT
Cosmic rays 10Be biennal data and their relationship to aurorae and sunspots
The galactic cosmic ray (C.R.) variations which should give information on three dimensional aspects of the heliospheric magnetic fields and on the solar wind, which modulate their influx into the Solar System were studied. In order to decode the information from the C.R. series it is necessary to know the mechanisms through which the modulation is produced. It it clear that a balance of effects with sources at different heliospheric latitudes results in the modulated C.R. intensity. It is found that the modulation of 10Be in polar ice may be due to at least two main contributions: (1) negative and in phase with the Solar flare activity modulating the cosmic ray flux in Forbush-type decreases, and (2) positive in phase with the appearance of large wind streams situated at both polar coronal holes. It is found that the high heliolatitude activity is related to a stable periodicity of 11.1y whereas the low heliolatitude activity contributes to the wondering of the solar cycles
Cosmic ray secular variations in terrestrial records and aurorae
The rediscovery that the Sun and the solar wind can undergo important changes on historical time scales has brought into question the stability of the cyclic behavior of past time series of solar and solar-terrestrial origin. It was found by Vector Fourier analysis that the solar 11 year cycle is present in the series of 10Be, delta 180, in ice cores and of thermoluminescence (TL) in sea sediments during the last Millennia with a frequency modulation, related to the Sun behavior, as tested by comparison with the Sunspot number R sub z series. It was shown that the cyclogram of the series of yearly Aurorae from 1721 to 1979 linear-regression-corrected-for-R sub z is straight for the periodicity zeta=11,1y, which indicates that such periodicity is constant in time corresponding to the only line present in the 11y band. The maxima of this component appear at the same time together with the high speed solar wind streams taking place in coronal holes situated in high heliolatitudes. It is evidenced that the 11 year cycle has undergone frequency oscillations on a time scale of two centuries, although it is very difficult to determine the periodicities with high accuracy
Levels of openness to Industry 4.0 and performance. An empirical analysis of manufacturing companies
A Monte Carlo Calculation of Atmospheric Muon and Neutrino Fluxes
Production of muons and neutrinos in cosmic ray interactions with the
atmosphere has been investigated with a cascade simulation program based on
Lund Monte Carlo programs. The resulting `conventional' muon and neutrino
fluxes (from decays) agree well with earlier calculations, whereas the
improved charm particle treatment used in this study gives significantly lower
`prompt' fluxes compared to earlier estimates. This implies better prospects
for detecting very high energy neutrinos from cosmic sources.Comment: 4 pages, uuencoded and gziped ps-fil
Reply to Comment on "Quantum dense key distribution"
In this Reply we propose a modified security proof of the Quantum Dense Key
Distribution protocol detecting also the eavesdropping attack proposed by
Wojcik in his Comment.Comment: To appear on PRA with minor change
The 50% advanced information rule of the quantum algorithms
The oracle chooses a function out of a known set of functions and gives to
the player a black box that, given an argument, evaluates the function. The
player should find out a certain character of the function through function
evaluation. This is the typical problem addressed by the quantum algorithms. In
former theoretical work, we showed that a quantum algorithm requires the number
of function evaluations of a classical algorithm that knows in advance 50% of
the information that specifies the solution of the problem. Here we check that
this 50% rule holds for the main quantum algorithms. In the structured
problems, a classical algorithm with the advanced information, to identify the
missing information should perform one function evaluation. The speed up is
exponential since a classical algorithm without advanced information should
perform an exponential number of function evaluations. In unstructured database
search, a classical algorithm that knows in advance 50% of the n bits of the
database location, to identify the n/2 missing bits should perform Order(2
power n/2) function evaluations. The speed up is quadratic since a classical
algorithm without advanced information should perform Order(2 power n) function
evaluations. The 50% rule identifies the problems solvable with a quantum sped
up in an entirely classical way, in fact by comparing two classical algorithms,
with and without the advanced information.Comment: 18 pages, submitted with minor changes to the International Journal
of Theoretical Physic
Experimental noise-resistant Bell-inequality violations for polarization-entangled photons
We experimentally demonstrate that violations of Bell's inequalities for
two-photon polarization-entangled states with colored noise are extremely
robust, whereas this is not the case for states with white noise. Controlling
the amount of noise by using the timing compensation scheme introduced by Kim
et al. [Phys. Rev. A 67, 010301(R) (2003)], we have observed violations even
for states with very high noise, in excellent agrement with the predictions of
Cabello et al. [Phys. Rev. A 72, 052112 (2005)].Comment: REVTeX4, 5 pages, 4 figure
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