Secure Sparse Gradient Aggregation in Distributed Architectures

Federated Learning allows multiple parties to train a model collaboratively while keeping data locally. Two main concerns when using Federated Learning are communication costs and privacy. A technique proposed to significantly reduce communication costs and increase privacy is Partial Weight Sharing (PWS). However, this method is insecure due to the possibility to reconstruct the original data from the partial gradients, called inversion attacks. In this paper, we propose a novel method to successfully combine these PWS and Secure Multi-Party Computation, a method for increasing privacy. This is done by making clients share the same part of their gradient, and adding noise to those entries, which are canceled on aggregation. We show that this method does not decrease the accuracy compared to existing methods while preserving privacy

Designs of magnetic atom-trap lattices for quantum simulation experiments

We have designed and realized magnetic trapping geometries for ultracold atoms based on permanent magnetic films. Magnetic chip based experiments give a high level of control over trap barriers and geometric boundaries in a compact experimental setup. These structures can be used to study quantum spin physics in a wide range of energies and length scales. By introducing defects into a triangular lattice, kagome and hexagonal lattice structures can be created. Rectangular lattices and (quasi-)one-dimensional structures such as ladders and diamond chain trapping potentials have also been created. Quantum spin models can be studied in all these geometries with Rydberg atoms, which allow for controlled interactions over several micrometers. We also present some nonperiodic geometries where the length scales of the traps are varied over a wide range. These tapered structures offer another way to transport large numbers of atoms adiabatically into subwavelength traps and back.Comment: 9 pages, 10 figure

A high-resolution magnetic record of drift sediments in the neighbourhood of mound provinces in the Porcupine Seabight

The Porcupine Seabight forms a deep embayment in the Atlantic margin, off the south-western coast of Ireland. Very-high resolution seismic profiling, acquired since 1997, revealed the presence of large (carbonate) mounds.In general, the mounds are surrounded by bottom-current related deposits. The changes of seismic characteristics within the uppermost unit are interpreted as phases in a slope parallel drift under changing oceanographic conditions.The magnetic susceptibility records of two giant piston cores (MD01-2450 and MD01-2452), taken respectively in the drift sediments at the SE-flank of a Belgica mound (eastern flank of the basin) and above a Magellan mound (northern flank of the basin), were analysed in order to provide a relative time frame and to investigate possible changes in paleoceanography and paleoclimatology.Core MD01-2450 enabled us to propose a relative dating of over 74 ka, which has been confirmed by comparing the intensity of the NRM (Natural Remanent Magnetization) to ARM (Anhysteretic Remanent Magnetization) ratio with known intensity data. Another very remarkable observation in this core is the presence of iron sulfides between 630 and 1080 cm depth. This local iron sulfide enrichment could be the result of an anaerobic process with sulfate reduction during a period of non-steady-state diagenesis.Core MD01-2452, located in the sediments on top of the buried Magellan mounds, shows more pronounced paleoclimatological changes than the core located at the SE-flank of the Belgica mound. Moreover, typical HL can be recognized very clearly from magnetic susceptibility and P-wave velocity data during the latest glacial. The influence of European HE in the northern part of the basin could be less than on the eastern flank. However, we should be bear in mind that currents seem to be much weaker in the Magellan province than in the Belgica province. These weaker currents can be responsible for better preserved and thus more pronounced paleoclimatological and paleoceanographic changes in the uppermost quaternary sediment layers

COCARDE: new view on old mounds – an international network of carbonate mound research

EGU2012-12550 Carbonate mounds are important contributors of life in different settings, from warm-water to cold-water environments, and throughout geological history. Research on modern cold-water coral carbonate mounds over the last decades made a major contribution to our overall understanding of these particular sedimentary systems. By looking to the modern carbonate mound community with cold-water corals as main framework builders, some fundamental questions could be addressed, until now not yet explored in fossil mound settings. The international network COCARDE (http://www.cocarde.eu) is a platform for exploring new insights in carbonate mound research of recent and ancient mound systems. The aim of the COCARDE network is to bring together scientific communities, studying Recent carbonate mounds in midslope environments in the present ocean and investigating fossil mounds spanning the whole Phanerozoic time, respectively. Scientific challenges in modern and ancient carbonate mound research got well defined during the ESF Magellan Workshop COCARDE in Fribourg, Switzerland (21.–24.01.2009). The Special Volume Cold-water Carbonate Reservoir systems in Deep Environments – COCARDE (Marine Geology, Vol. 282) was the major outcome of this meeting and highlights the diversity of Recent arbonate mound studies. The following first jointWorkshop and Field Seminar held in Oviedo, Spain (16.–20.09.2009) highlighted ongoing research from both Recent and fossil academic groups integrating the message from the industry. The field seminar focused on mounds from the Carboniferous platform of Asturias and Cantabria, already intensively visited by industrial and academic researchers. However, by comparing ancient, mixed carbonate-siliciclastic mound systems of Cantabria with the Recent ones in the Porcupine Seabight, striking similarities in their genesis and processes in mound development asked for an integrated drilling campaign to understand better the 3D internal mound build-up. The Oviedo Workshop and Field Seminar led to the submission of a White Paper on Carbonate Mound Drilling and the initiation of the ESF European Research Network Programme Cold-Water Carbonate Mounds in Shallow and Deep Time – The European Research Network (COCARDE-ERN) launched in June 2011. The second COCARDE Workshop and Field Seminar was held in Rabat, Morocco (24.–30.10.2011) and thematically focussed on carbonate mounds of(f) Morocco. The compact workshop invited students from Moroccan Universities to experience ongoing carbonate mound research in Recent and Ancient environments of Morocco. Two Round Tables discussed innovative approaches in carbonate mound research in Morocco (Recent vs. Ancient - offshore vs. onshore) and reviewed together with oil industry opportunities of international collaboration. The outcome of this workshop will lead into joint research projects, drilling campaigns on- and offshore, and expansion of COCARDE onto the African continent