784 research outputs found
Projection of two biphoton qutrits onto a maximally entangled state
Bell state measurements, in which two quantum bits are projected onto a
maximally entangled state, are an essential component of quantum information
science. We propose and experimentally demonstrate the projection of two
quantum systems with three states (qutrits) onto a generalized maximally
entangled state. Each qutrit is represented by the polarization of a pair of
indistinguishable photons - a biphoton. The projection is a joint measurement
on both biphotons using standard linear optics elements. This demonstration
enables the realization of quantum information protocols with qutrits, such as
teleportation and entanglement swapping.Comment: 4 pages, 3 figures, published versio
The biaxial nonlinear crystal BiB3O6 as a polarization entangled photon source using non-collinear type-II parametric down-conversion
We describe the full characterization of the biaxial nonlinear crystal BiB3O6
(BiBO) as a polarization entangled photon source using non-collinear type-II
parametric down-conversion. We consider the relevant parameters for crystal
design, such as cutting angles, polarization of the photons, effective
nonlinearity, spatial and temporal walk-offs, crystal thickness and the effect
of the pump laser bandwidth. Experimental results showing entanglement
generation with high rates and a comparison to the well investigated
beta-BaB2O4 (BBO) crystal are presented as well. Changing the down-conversion
crystal of a polarization entangled photon source from BBO to BiBO enhances the
generation rate as if the pump power was increased by more than three times.
Such an improvement is currently required for the generation of multiphoton
entangled states.Comment: 15 pages, 13 figures, published versio
Efficient semi-static secure broadcast encryption scheme
In this paper, we propose a semi-static secure broadcast encryption scheme with constant-sized private keys and ciphertexts. Our result improves the semi-static secure broadcast encryption scheme introduced by Gentry and Waters. Specifically, we reduce the private key and ciphertext size by half. By applying the generic transformation proposed by Gentry and Waters, our scheme also achieves adaptive security. Finally, we present an improved implementation idea which can reduce the ciphertext size in the aforementioned generic transformation
SemLAV: Local-As-View Mediation for SPARQL Queries
International audienceThe Local-As-View(LAV) integration approach aims at querying heterogeneous data in dynamic environments. In LAV, data sources are described as views over a global schema which is used to pose queries. Query processing requires to generate and execute query rewritings, but for SPARQL queries, the LAV query rewritings may not be generated or executed in a reasonable time. In this paper, we present SemLAV, an alternative technique to process SPARQL queries over a LAV integration system without generating rewritings. SemLAV executes the query against a partial instance of the global schema which is built on-the-fly with data from the relevant views. The paper presents an experimental study for SemLAV, and compares its performance with traditional LAV-based query processing techniques. The results suggest that SemLAV scales up to SPARQL queries even over a large number of views, while it significantly outperforms traditional solutions
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