Dissipation-induced symmetry breaking in a driven optical lattice

We analyze the atomic dynamics in an ac driven periodic optical potential which is symmetric in both time and space. We experimentally demonstrate that in the presence of dissipation the symmetry is broken, and a current of atoms through the optical lattice is generated as a result

Imagines hominum o simulacra deororum? Le impressioni 'naturalistiche' sui pesi da telaio della bassa Pianura Padana

Among the image-printed loom weights from northern Italy we can identify a very small category featuring images drawn with a 'naturalistic' intention, and not as a result of 'combining' of recurrent geometrical symbols (which we usually call 'fishbone/ear', 'X', 'wheel/flower', even if their real meaning is unknown). The ânaturalisticâ images here taken into account seem to recall something involved with popular devotion. The first one (pc.1), appears to represent a sort of 'temple', as another one (pc.2), very similar to the former, found on a loom weight from the same area, does; a temple whose tympanum in both cases contains an unclear symbol (respectively, a circular draw and a 'X'), and whose walls enclose a big vanished figure, in the first case, or a bewildering rhombus-shaped drawing, in the second case; the contact point of both printed reliefs is the small figure at the bottom of the square, which has to be interpreted as a phallic figure as it seems. The second image we examined (pc.3) clearly represents a man, with no other characterizations than his strange pose, which means that heâs decidedly directing himself towards his right side. The hypothesis by D. Rigato of identifying him as Hercules, seems to be sustained on the one hand by the nudity of the body and because of the popularity of the Hercules cult in the area where the loom weight was found; on the other hand, the image doesnât show any other element, or any typical action which the Hero was known by in the antiquity. The characterization of the examined 'naturalistic' printed-images lets us think about an extremely popular version of sacred or devotional, also 'apotropaic', subjects. The comparison with the large number of other printed-images on Cisalpine loom weights, whose abstract-geometrical compound drawings appear often to be followed by letters, or entire words (personal names and surnames), seems to warn about what could have been the real function of printed images: therefore, also images of sacred origin could have been used to mark - as a âsignatureâ of a single man, but also of a group of people, who recognizes himself in that subject - a certain category of production, was it clay or textile

Plasma harmonics Lissajous measurements

June 17-21 200

Using adiabatic coupling techniques in atom-chip waveguide structures

Adiabatic techniques are well known tools in multi-level electron systems to transfer population between different states with high fidelity. Recently it has been realised that these ideas can also be used in ultra-cold atom systems to achieve coherent manipulation of the atomic centre-of-mass states. Here we present an investigation into a realistic setup using three atomic waveguides created on top of an atom chip and show that such systems hold large potential for the observation of adiabatic phenomena in experiments.Comment: 10 pages, 6 figures, accepted for publication in Physica Scripta for the CEWQO2009 proceeding

Analysis of the entanglement between two individual atoms using global Raman rotations

Making use of the Rydberg blockade, we generate entanglement between two atoms individually trapped in two optical tweezers. In this paper we detail the analysis of the data and show that we can determine the amount of entanglement between the atoms in the presence of atom losses during the entangling sequence. Our model takes into account states outside the qubit basis and allows us to perform a partial reconstruction of the density matrix describing the two atom state. With this method we extract the amount of entanglement between pairs of atoms still trapped after the entangling sequence and measure the fidelity with respect to the expected Bell state. We find a fidelity $F_{\rm pairs} =0.74(7)$ for the 62% of atom pairs remaining in the traps at the end of the entangling sequence

Nano Positioning of Single Atoms in a Micro Cavity

The coupling of individual atoms to a high-finesse optical cavity is precisely controlled and adjusted using a standing-wave dipole-force trap, a challenge for strong atom-cavity coupling. Ultracold Rubidium atoms are first loaded into potential minima of the dipole trap in the center of the cavity. Then we use the trap as a conveyor belt that we set into motion perpendicular to the cavity axis. This allows us to repetitively move atoms out of and back into the cavity mode with a repositioning precision of 135 nm. This makes possible to either selectively address one atom of a string of atoms by the cavity, or to simultaneously couple two precisely separated atoms to a higher mode of the cavity.Comment: 4 pages 5 figure

Deterministic single-atom excitation via adiabatic passage and Rydberg blockade

We propose to use adiabatic rapid passage with a chirped laser pulse in the strong dipole blockade regime to deterministically excite only one Rydberg atom from randomly loaded optical dipole traps or optical lattices. The chirped laser excitation is shown to be insensitive to the random number \textit{N} of the atoms in the traps. Our method overcomes the problem of the $\sqrt {N}$ dependence of the collective Rabi frequency, which was the main obstacle for deterministic single-atom excitation in the ensembles with unknown \textit{N}, and can be applied for single-atom loading of dipole traps and optical lattices.Comment: 6 pages, 5 figures. Version 5 is expanded and submitted to PRA. Typo in Fig.4 corrected in Version 2. Version 3 and 4 are duplicates of V

Sublattice addressing and spin-dependent motion of atoms in a double-well lattice

We load atoms into every site of an optical lattice and selectively spin flip atoms in a sublattice consisting of every other site. These selected atoms are separated from their unselected neighbors by less than an optical wavelength. We also show spin-dependent transport, where atomic wave packets are coherently separated into adjacent sites according to their internal state. These tools should be useful for quantum information processing and quantum simulation of lattice models with neutral atoms

Observers are a key source of detection heterogeneity and biased occupancy estimates in species monitoring

Reliable assessments of population status and trends underpin conservation management efforts but are complicated by the fact that imperfect detection is ubiquitous in monitoring data. We explore the most commonly considered variables believed to influence detection probabilities, quantifying how they influence detectability and assessing how occupancy rates are impacted when a variable is ignored. To do so, we used data from two multi-species amphibian monitoring programmes, collected by volunteers and professional surveyors. Our results suggest that although detection rates varied substantially in relation to commonly considered factors such as seasonal and annual effects, ignoring these factors in the analysis of monitoring data had negligible effect on estimated occupancy rates. Variation among surveyors in detection probabilities turned out to be most important. It was high and failing to account for it led to occupancy being underestimated. Importantly, we identified that heterogeneity among observers was as high for professional surveyors as for volunteers, highlighting that this issue is not restricted to citizen-science monitoring. Occupancy modelling has greatly improved the reliability of inference from species monitoring data, yet capturing the relevant sources of variation remains a challenge. Our results highlight that variation among surveyors is a key source of heterogeneity, and that this issue is just as pertinent to data collected by experts as by volunteers. Detection heterogeneity should be accounted for when analysing monitoring data. Furthermore, efforts to increase training of field crews and collecting data to quantify differences between observer abilities are important to avoid biased inference resulting from unmodelled observer differences