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Search Results: 1 - 10 of 476948 matches for " N. J. Van Druten "
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Atom chips and one-dimensional Bose gases
Isabelle Bouchoule,N. J. Van Druten,Christoph I. Westbrook
Physics , 2009,
Abstract: In this review article, we describe the studies of 1D gases realised on atom-chip experiments.
Controlling spin motion and interactions in a one-dimensional Bose gas
P. Wicke,S. Whitlock,N. J. van Druten
Physics , 2010,
Abstract: Experiments on ultracold gases offer unparalleled opportunities to explore quantum many-body physics, with excellent control over key parameters including temperature, density, interactions and even dimensionality. In some systems, atomic interactions can be adjusted by means of magnetic Feshbach resonances, which have played a crucial role in realizing new many-body phenomena. However, suitable Feshbach resonances are not always available, and they offer limited freedom since the magnetic field strength is the only control parameter. Here we show a new way to tune interactions in one-dimensional quantum gases using state-dependent dressed potentials, enabling control over non-equilibrium spin motion in a two-component gas of 87Rb. The accessible range includes the point of spin-independent interactions where exact quantum many-body solutions are available and the point where spin motion is frozen. This versatility opens a new route to experiments on spin waves, spin-"charge" separation and the relation between superfluidity and magnetism in low-dimensional quantum gases.
Spin modulation instabilities and phase separation dynamics in trapped two-component Bose condensates
Ivana Vidanovic,N. J. van Druten,Masudul Haque
Physics , 2012, DOI: 10.1088/1367-2630/15/3/035008
Abstract: In the study of trapped two-component Bose gases, a widely used dynamical protocol is to start from the ground state of a one-component condensate and then switch half the atoms into another hyperfine state. The slightly different intra-component and inter-component interactions can then lead to highly nontrivial dynamics. We study and classify the possible subsequent dynamics, over a wide variety of parameters spanned by the trap strength and by the inter- to intra-component interaction ratio. A stability analysis suited to the trapped situation provides us with a framework to explain the various types of dynamics in different regimes.
Microtrap arrays on magnetic film atom chips for quantum information science
V. Y. F. Leung,A. Tauschinsky,N. J. van Druten,R. J. C. Spreeuw
Physics , 2011, DOI: 10.1007/s11128-011-0295-1
Abstract: 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.
Box traps on an atom chip for one-dimensional quantum gases
J. J. P. van Es,P. Wicke,A. H. van Amerongen,C. Rétif,S. Whitlock,N. J. van Druten
Physics , 2009, DOI: 10.1088/0953-4075/43/15/155002
Abstract: We present the implementation of tailored trapping potentials for ultracold gases on an atom chip. We realize highly elongated traps with box-like confinement along the long, axial direction combined with conventional harmonic confinement along the two radial directions. The design, fabrication and characterization of the atom chip and the box traps is described. We load ultracold ($\lesssim1 \mu$K) clouds of $^{87}$Rb in a box trap, and demonstrate Bose-gas focusing as a means to characterize these atomic clouds in arbitrarily shaped potentials. Our results show that box-like axial potentials on atom chips are very promising for studies of one-dimensional quantum gases.
Three-dimensional character of atom-chip-based rf-dressed potentials
J. J. P. van Es,S. Whitlock,T. Fernholz,A. H. van Amerongen,N. J. van Druten
Physics , 2008, DOI: 10.1103/PhysRevA.77.063623
Abstract: We experimentally investigate the properties of radio-frequency-dressed potentials for Bose-Einstein condensates on atom chips. The three-dimensional potential forms a connected pair of parallel waveguides. We show that rf-dressed potentials are robust against the effect of small magnetic-field variations on the trap potential. Long-lived dipole oscillations of condensates induced in the rf-dressed potentials can be tuned to a remarkably low damping rate. We study a beam-splitter for Bose-Einstein condensates and show that a propagating condensate can be dynamically split in two vertically separated parts and guided along two paths. The effect of gravity on the potential can be tuned and compensated for using a rf-field gradient.
Yang-Yang thermodynamics on an atom chip
A. H. van Amerongen,J. J. P. van Es,P. Wicke,K. V. Kheruntsyan,N. J. van Druten
Physics , 2007, DOI: 10.1103/PhysRevLett.100.090402
Abstract: We investigate the behavior of a weakly interacting nearly one-dimensional (1D) trapped Bose gas at finite temperature. We perform in situ measurements of spatial density profiles and show that they are very well described by a model based on exact solutions obtained using the Yang-Yang thermodynamic formalism, in a regime where other, approximate theoretical approaches fail. We use Bose-gas focusing [Shvarchuck etal., Phys. Rev. Lett. 89, 270404 (2002)] to probe the axial momentum distribution of the gas, and find good agreement with the in situ results.
Yang-Yang thermometry and momentum distribution of a trapped one-dimensional Bose gas
M. J. Davis,P. B. Blakie,A. H. van Amerongen,N. J. van Druten,K. V. Kheruntsyan
Physics , 2011, DOI: 10.1103/PhysRevA.85.031604
Abstract: We describe the use of the exact Yang-Yang solutions for the one-dimensional Bose gas to enable accurate kinetic-energy thermometry based on the root-mean-square width of an experimentally measured momentum distribution. Furthermore, we use the stochastic projected Gross-Pitaevskii theory to provide the first quantitative description of the full momentum distribution measurements of Van Amerongen et al., Phys. Rev. Lett. 100, 090402 (2008). We find the fitted temperatures from the stochastic projected Gross-Pitaevskii approach are in excellent agreement with those determined by Yang-Yang kinetic-energy thermometry.
Adsorbate dynamics on a silica-coated gold surface measured by Rydberg Stark spectroscopy
J. Naber,S. Machluf,L. Torralbo-Campo,M. L. Soudijn,N. J. van Druten,H. B. van Linden van den Heuvell,R. J. C. Spreeuw
Physics , 2015,
Abstract: Trapping a Rydberg atom close to a surface is an important step towards the realisation of many proposals of quantum information or hybrid quantum systems. One of the challenges in these experiments is to overcome the electric field emanating from contaminations on the surface. Here we report on measurements of an electric field created by $^{87}$Rb atoms absorbed on a 25$\,$nm thick layer of SiO$_2$, covering a 90$\,$nm layer of Au. The electric field is measured using a two-photon transition to the 23$D_{5/2}$ and 25$S_{1/2}$ state. The electric field value that we measure is higher than typical values measured above metal surfaces, but is consistent with other measurements above SiO$_2$ surfaces. In addition, we measure the temporal behaviour of the field and observe that we can reduce it in a single experimental cycle, using UV light or by mildly heating the surface, whereas the buildup of the field takes thousands of cycles. We explain these results by a change in the ad-atoms distribution on the surface. These results indicate that the stray electric field can be reduced, opening new possibilities for experiments with trapped Rydberg atoms near surfaces.
Impact of Bisphenol A (BPA) and Free Fatty Acids (FFA) on Th2 Cytokine Secretion from INS-1 Cells  [PDF]
Johan N. van Oppen, Eugen J. Verspohl
Pharmacology & Pharmacy (PP) , 2013, DOI: 10.4236/pp.2013.45065
Abstract: Bisphenol A (BPA) is used in huge amounts for many plastic products and is a hormone (estrogen) disrupting agent. BPA as well as FFAs may be deleterious for the immune system. The aim was to identify Th2 cytokines and some of their signal transduction mechanisms in INS-1 cells, an insulin secreting cell line. Screening using a proteome profile indicated an increase of IL-1, IL-2, IL-4, IL-6, IL-10, IL-13 and IL-17 by BPA. Also FFAs (in combination with LPS) were positive. In detailed quantitative measurements, these results were confirmedly indicating a complex array of pro-and anti-inflammatory potential. The interaction of BPA with 17β-estradiol was non-additive with respect to IL-4 and IL-6 release and additive with respect to FFA interaction indicating same and different mechanisms of action, respecttively. As signal transduction PI3K (Wortmannin-sensitive) and STAT-3/6 (Tofacitinib-sensitive) are involved in various effects, INS-1 cells release several cytokines due to BPA and FFA attack which may be involved in disturbance of glucose homoeostasis and type 1 diabetes.
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