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Search Results: 1 - 10 of 1202 matches for " Herwig Ott "
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Scanning electron microscopy of cold gases
Bodhaditya Santra,Herwig Ott
Physics , 2015, DOI: 10.1088/0953-4075/48/12/122001
Abstract: Ultracold quantum gases offer unique possibilities to study interacting many-body quantum systems. Probing and manipulating such systems with ever increasing degree of control requires novel experimental techniques. Scanning electron microscopy is a high resolution technique which can be used for in situ imaging, single site addressing in optical lattices and precision density engineering. Here, we review recent advances and achievements obtained with this technique and discuss future perspectives.
Dynamically Probing Ultracold Lattice Gases via Rydberg Molecules
Torsten Manthey,Thomas Niederprüm,Oliver Thomas,Herwig Ott
Physics , 2015, DOI: 10.1088/1367-2630/17/10/103024
Abstract: We show that the excitation of long-range Rydberg molecules in a three-dimensional optical lattice can be used as a position- and time-sensitive probe of the site occupancy in the system. To this end, we detect the ions which are continuously generated by the decay of the formed Rydberg molecules. While a superfluid gas shows molecule formation for all parameters, a Mott insulator with $n=1$ filling reveals a strong suppression of the number of formed molecules. In the limit of weak probing, the technique can be used to probe the superfluid to Mott-insulator transition in real-time. Our method can be extended to higher fillings and has various applications for the real-time diagnosis and manipulation of ultracold lattice gases.
A laser system for the excitation of rubidium Rydberg states using second harmonic generation in a PPLN waveguide crystal
Andreas Koglbauer,Peter Würtz,Tatjana Gericke,Herwig Ott
Physics , 2010, DOI: 10.1007/s00340-011-4530-3
Abstract: We report on a laser system at a wavelength of 495 nm which is suitable for the excitations of low lying Rydberg states of rubidium atoms. The system is based on frequency doubling of a seeded diode laser in a periodically poled waveguide crystal. We achieve an output power of up to 35 mW and prove the single frequency performance by direct two photon laser spectroscopy of the rubidium 14D_5/2 and 14D_3/2 states. The measured fine structure splitting is consistent with quantum defect theory calculations.
Negative differential conductivity in an interacting quantum gas
Ralf Labouvie,Bodhaditya Santra,Simon Heun,Sandro Wimberger,Herwig Ott
Physics , 2014, DOI: 10.1103/PhysRevLett.115.050601
Abstract: Negative differential conductivity (NDC) is a widely exploited effect in modern electronic components. Here, a proof-of-principle is given for the observation of NDC in a quantum transport device for neutral atoms employing a multi-mode tunneling junction. The transport of the many-body quantum system is governed by the interplay between the tunnel coupling, the interaction energy and the thermodynamics of intrinsic collisions, which turn the coherent coupling into a hopping process. The resulting current voltage characteristics exhibit NDC, for which we identify a new microscopic physical mechanism. Our study opens new ways for the future implementation and control of complex neutral atom quantum circuits.
Non-equilibrium steady-states in a driven-dissipative superfluid
Ralf Labouvie,Bodhaditya Santra,Simon Heun,Herwig Ott
Physics , 2015,
Abstract: We experimentally study a driven-dissipative Josephson junction array, realized with a weakly interacting Bose Einstein condensate residing in a one-dimensional optical lattice. Engineered losses on one site act as a local dissipative process, while tunneling from the neighboring sites constitutes the driving force. We characterize the emerging steady-states of this atomtronic device. With increasing dissipation strength $\gamma$ the system crosses from a superfluid state, characterized by a coherent Josephson current into the lossy site to a resistive state, characterized by an incoherent hopping transport. For intermediate values of $\gamma$, the system exhibits bistability, where a superfluid and a resistive branch coexist. We also study the relaxation dynamics towards the steady-state, where we find a critical slowing down, indicating the presence of a non-equilibrium phase transition.
The Misleading Use of “Enthalpy” in an Energy Conversion Analysis  [PDF]
Heinz Herwig
Natural Science (NS) , 2014, DOI: 10.4236/ns.2014.611085
Abstract: The frequently used thermodynamic state quantity enthalpy H turns out to be very problematic when applied in an energy conversion analysis. Due to the fact that H combines two terms, the internal energy U and the product pV, the interpretation of what H means in physical terms is often obscure and leads to various misinterpretations. Several examples are given and interpreted twice,i.e.with and without referring to enthalpy.
High Resolution Imaging of Single Atoms in a Quantum Gas
Tatjana Gericke,Peter Würtz,Daniel Reitz,Tim Langen,Herwig Ott
Physics , 2008,
Abstract: Our knowledge on ultracold quantum gases is strongly influenced by our ability to probe these objects. In situ imaging combined with single atom sensitivity is an especially appealing scenario as it can provide direct information on the structure and the correlations of such systems. For a precise characterization a high spatial resolution is mandatory. In particular, the perspective to study quantum gases in optical lattices makes a resolution well below one micrometer highly desirable. Here, we report on a novel microscopy technique which is based on scanning electron microscopy and allows for the detection of single atoms inside a quantum gas with a spatial resolution of better than 150 nm. Imaging a Bose-Einstein condensate in a one-dimensional optical lattice with 600 nm period we demonstrate single site addressability in a sub-um optical lattice. The technique offers exciting possibilities for the preparation, manipulation and analysis of quantum gases.
Cross-dimensional phase transition from an array of 1D Luttinger liquids to a 3D Bose-Einstein condensate
Andreas Vogler,Ralf Labouvie,Giovanni Barontini,Sebastian Eggert,Vera Guarrera,Herwig Ott
Physics , 2014, DOI: 10.1103/PhysRevLett.113.215301
Abstract: We study the thermodynamic properties of a 2D array of coupled one-dimensional Bose gases. The system is realized with ultracold bosonic atoms loaded in the potential tubes of a two-dimensional optical lattice. For negligible coupling strength, each tube is an independent weakly interacting 1D Bose gas featuring Tomonaga Luttinger liquid behavior. By decreasing the lattice depth, we increase the coupling strength between the 1D gases and allow for the phase transition into a 3D condensate. We extract the phase diagram for such a system and compare our results with theoretical predictions. Due to the high effective mass across the periodic potential and the increased 1D interaction strength, the phase transition is shifted to large positive values of the chemical potential. Our results are prototypical to a variety of low-dimensional systems, where the coupling between the subsystems is realized in a higher spatial dimension such as coupled spin chains in magnetic insulators.
Giant cross section for molecular ion formation in ultracold Rydberg gases
Thomas Niederprüm,Oliver Thomas,Torsten Manthey,Tobias M. Weber,Herwig Ott
Physics , 2015, DOI: 10.1103/PhysRevLett.115.013003
Abstract: We have studied the associative ionization of a Rydberg atom and a ground state atom in an ultracold Rydberg gas. The measured scattering cross section is three orders of magnitude larger than the geometrical size of the produced molecule. This giant enhancement of the reaction kinetics is due to an efficient directed mass transport which is mediated by the Rydberg electron. We also find that the total inelastic scattering cross section is given by the geometrical size of the Rydberg electron's wavefunction.
Experimental demonstration of single-site addressability in a two-dimensional optical lattice
Peter Würtz,Tim Langen,Tatjana Gericke,Andreas Koglbauer,Herwig Ott
Physics , 2009, DOI: 10.1103/PhysRevLett.103.080404
Abstract: We demonstrate single site addressability in a two-dimensional optical lattice with 600 nm lattice spacing. After loading a Bose-Einstein condensate in the lattice potential we use a focused electron beam to remove atoms from selected sites. The patterned structure is subsequently imaged by means of scanning electron microscopy. This technique allows us to create arbitrary patterns of mesoscopic atomic ensembles. We find that the patterns are remarkably stable against tunneling diffusion. Such micro-engineered quantum gases are a versatile resource for applications in quantum simulation, quantum optics and quantum information processing with neutral atoms.
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