Improved detection of small atom numbers through image processing

We demonstrate improved detection of small trapped atomic ensembles through advanced post-processing and optimal analysis of absorption images. A fringe removal algorithm reduces imaging noise to the fundamental photon-shot-noise level and proves beneficial even in the absence of fringes. A maximum-likelihood estimator is then derived for optimal atom-number estimation and is applied to real experimental data to measure the population differences and intrinsic atom shot-noise between spatially separated ensembles each comprising between 10 and 2000 atoms. The combined techniques improve our signal-to-noise by a factor of 3, to a minimum resolvable population difference of 17 atoms, close to our ultimate detection limit.Comment: 4 pages, 3 figure

Magnetic-film atom chip with 10 μ\mum period lattices of microtraps for quantum information science with Rydberg atoms

We describe the fabrication and construction of a setup for creating lattices of magnetic microtraps for ultracold atoms on an atom chip. The lattice is defined by lithographic patterning of a permanent magnetic film. Patterned magnetic-film atom chips enable a large variety of trapping geometries over a wide range of length scales. We demonstrate an atom chip with a lattice constant of 10 $\mu$m, suitable for experiments in quantum information science employing the interaction between atoms in highly-excited Rydberg energy levels. The active trapping region contains lattice regions with square and hexagonal symmetry, with the two regions joined at an interface. A structure of macroscopic wires, cut out of a silver foil, was mounted under the atom chip in order to load ultracold $^{87}$Rb atoms into the microtraps. We demonstrate loading of atoms into the square and hexagonal lattice sections simultaneously and show resolved imaging of individual lattice sites. Magnetic-film lattices on atom chips provide a versatile platform for experiments with ultracold atoms, in particular for quantum information science and quantum simulation.Comment: 7 pages, 7 figure

Two Conceptions of Democracy in the Council of the EU: Narrow and Broad

Since the entry into force of the Lisbon Treaty, the Council is explicitly understood as a democratic actor in a decision-making system that is legitimated on the basis of a democratic rationale. While this formalisation in the Lisbon Treaty of the Council as a democratic actor is to be welcomed as an important step in a longer-standing process, it remains unclear which normative requirements result from it. This point is illustrated in this paper with reference to the principle of transparency. It discerns the role of transparency in two competing conceptions at the Council level, representing a narrow, and a broad perspective on democracy. It is argued that below a minimal threshold of transparency, Council democracy cannot function. Above this threshold, in turn, transparency is likely to make Council democracy function better

Over lichtemissie: Albert Einstein en de vroege geschiedenis van de Nederlandse Natuurkundige Vereniging

Op 29 april 1922 gaf Albert Einstein een lezing voor de Nederlandse Natuurkundige Vereniging op het Natuurkundig Laboratorium aan de Plantage Muidergracht te Amsterdam. Hij deed er verslag van een experiment dat hij zo’n zes maanden eerder had voorgesteld en dat zou hebben moeten uitmaken of licht uit deeltjes dan wel uit golven bestond

Microtrap arrays on magnetic film atom chips for quantum information science.

We present two different strategies for developing a quantum information science platform, based on our experimental results with magnetic microtrap arrays on a magnetic-film atom chip. The first strategy aims for mesoscopic ensemble qubits in a lattice of ~5 {\mu}m period, so that qubits can be individually addressed and interactions can be mediated by Rydberg excitations. The second strategy aims for direct quantum simulators using sub-optical lattices of ~100 nm period. These would allow the realization of condensed matter inspired quantum many-body systems, such as Hubbard models in new parameter regimes. The two approaches raise quite different issues, some of which are identified and discussed.Comment: 10 pages, 6 figures, submitted to special issue "Quantum Information with Neutral Particles" of "Quantum Information Processing