David Gross-Amblard

Learn More
This technical note supplies an affirmative answer to a question raised in a recent pre-print in the context of a “matrix recovery” problem. Assume one samples m Hermitian matrices X1, . . . , Xm with replacement from a finite collection. The deviation of the sum X1+ · · ·+Xm from its expected value in terms of the operator norm can be estimated by an(More)
Xml streams are valuable, continuous, high-throughput sources of information whose owners must be protected against illegal redistributions. Watermarking is a known technique for hiding copyrights marks within documents, thus preventing redistributions. Here, we introduce a watermarking algorithm for Xml streams so that (i) the watermark embedding and(More)
The problem of retrieving phase information from amplitude measurements alone has appeared in many scientific disciplines over the last century. PhaseLift is a recently introduced algorithm for phase recovery that is computationally efficient, numerically stable, and comes with rigorous performance guarantees. PhaseLift is optimal in the sense that the(More)
In this work we analyze the problem of phase retrieval from Fourier measurements with random diffraction patterns. To this end, we consider the recently introduced PhaseLift algorithm, which expresses the problem in the language of convex optimization. We provide recovery guarantees which require O(log d) different diffraction patterns, thus improving on(More)
In this paper, we study how artificial facts can be added to an RDFS ontology. Artificial facts are an easy way of proving the ownership of an ontology: If another ontology contains the artificial fact, it has probably been taken from the original ontology. We show how the ownership of an ontology can be established with provably tight probability bounds,(More)
We present a simple way to quantize the well-known Margulis expander map. The result is a quantum expander which acts on discrete Wigner functions in the same way the classical Margulis expander acts on probability distributions. The quantum version shares all essential properties of the classical counterpart, e.g., it has the same degree and spectrum.(More)
Due to the ease of digital copy, watermarking is crucial to protect the intellectual property of rights owners. We propose an effective watermarking method for vectorial geographical databases, with the focus on the buildings layer. Embedded watermarks survive common geographical filters, including the essential squaring and simplification transformations,(More)