4,603 research outputs found
Delayed - Choice Entanglement - Swapping with Vacuum-One Photon Quantum States
We report the experimental realization of a recently discovered quantum
information protocol by Asher Peres implying an apparent non-local quantum
mechanical retrodiction effect. The demonstration is carried out by applying a
novel quantum optical method by which each singlet entangled state is
physically implemented by a two-dimensional subspace of Fock states of a mode
of the electromagnetic field, specifically the space spanned by the vacuum and
the one photon state, along lines suggested recently by E. Knill et al., Nature
409, 46 (2001) and by M. Duan et al., Nature 414, 413 (2001). The successful
implementation of the new technique is expected to play an important role in
modern quantum information and communication and in EPR quantum non-locality
studies
On the use of nearest neighbors in finance
The paper focuses on the conditions of the use of the nearest neighbors method analysing the impact of the Euclidean distance and in sample predictions, the choice of the neighbors, the number of neighbors and the distance between the neighbors.Nearest neighbors – Forecasting
Swarm-Based Spatial Sorting
Purpose: To present an algorithm for spatially sorting objects into an
annular structure. Design/Methodology/Approach: A swarm-based model that
requires only stochastic agent behaviour coupled with a pheromone-inspired
"attraction-repulsion" mechanism. Findings: The algorithm consistently
generates high-quality annular structures, and is particularly powerful in
situations where the initial configuration of objects is similar to those
observed in nature. Research limitations/implications: Experimental evidence
supports previous theoretical arguments about the nature and mechanism of
spatial sorting by insects. Practical implications: The algorithm may find
applications in distributed robotics. Originality/value: The model offers a
powerful minimal algorithmic framework, and also sheds further light on the
nature of attraction-repulsion algorithms and underlying natural processes.Comment: Accepted by the Int. J. Intelligent Computing and Cybernetic
Cosmological Density and Power Spectrum from Peculiar Velocities: Nonlinear Corrections and PCA
We allow for nonlinear effects in the likelihood analysis of galaxy peculiar
velocities, and obtain ~35%-lower values for the cosmological density parameter
Om and the amplitude of mass-density fluctuations. The power spectrum in the
linear regime is assumed to be a flat LCDM model (h=0.65, n=1, COBE) with only
Om as a free parameter. Since the likelihood is driven by the nonlinear regime,
we "break" the power spectrum at k_b=0.2 h/Mpc and fit a power law at k>k_b.
This allows for independent matching of the nonlinear behavior and an unbiased
fit in the linear regime. The analysis assumes Gaussian fluctuations and
errors, and a linear relation between velocity and density. Tests using proper
mock catalogs demonstrate a reduced bias and a better fit. We find for the
Mark3 and SFI data Om_m=0.32+-0.06 and 0.37+-0.09 respectively, with
sigma_8*Om^0.6 = 0.49+-0.06 and 0.63+-0.08, in agreement with constraints from
other data. The quoted 90% errors include cosmic variance. The improvement in
likelihood due to the nonlinear correction is very significant for Mark3 and
moderately so for SFI. When allowing deviations from LCDM, we find an
indication for a wiggle in the power spectrum: an excess near k=0.05 and a
deficiency at k=0.1 (cold flow). This may be related to the wiggle seen in the
power spectrum from redshift surveys and the second peak in the CMB anisotropy.
A chi^2 test applied to modes of a Principal Component Analysis (PCA) shows
that the nonlinear procedure improves the goodness of fit and reduces a spatial
gradient of concern in the linear analysis. The PCA allows addressing spatial
features of the data and fine-tuning the theoretical and error models. It shows
that the models used are appropriate for the cosmological parameter estimation
performed. We address the potential for optimal data compression using PCA.Comment: 18 pages, LaTex, uses emulateapj.sty, ApJ in press (August 10, 2001),
improvements to text and figures, updated reference
Experimental generalized quantum suppression law in Sylvester interferometers
Photonic interference is a key quantum resource for optical quantum
computation, and in particular for so-called boson sampling machines. In
interferometers with certain symmetries, genuine multiphoton quantum
interference effectively suppresses certain sets of events, as in the original
Hong-Ou-Mandel effect. Recently, it was shown that some classical and
semi-classical models could be ruled out by identifying such suppressions in
Fourier interferometers. Here we propose a suppression law suitable for
random-input experiments in multimode Sylvester interferometers, and verify it
experimentally using 4- and 8-mode integrated interferometers. The observed
suppression is stronger than what is observed in Fourier interferometers of the
same size, and could be relevant to certification of boson sampling machines
and other experiments relying on bosonic interference.Comment: 5 pages, 3 figures + 11 pages, 3 figures Supplementary Informatio
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