Bright Bose-Einstein gap solitons of atoms with repulsive interaction

We report on the first experimental observation of bright matter wave solitons for 87Rb atoms with repulsive atom-atom interaction. This counterintuitive situation arises inside a weak periodic potential, where anomalous dispersion can be realized at the Brillouin zone boundary. If the coherent atomic wave packet is prepared at the corresponding band edge, a bright soliton is formed inside the gap. The strength of our system is the precise control of preparation and real time manipulation, allowing the systematic investigation of gap solitons.     

Inconsistency in the application of the adiabatic theorem

The adiabatic theorem states that an initial eigenstate of a slowly varying Hamiltonian remains close to an instantaneous eigenstate of the Hamiltonian at a later time. We show that a perfunctory application of this statement is problematic if the change in eigenstate is significant, regardless of how closely the evolution satisfies the requirements of the adiabatic theorem. We also introduce an example of a two-level system with an exactly solvable evolution to demonstrate the inapplicability of the adiabatic approximation for a particular slowly varying Hamiltonian.     

Dispersion management for atomic matter waves

We demonstrate the control of the dispersion of matter wave packets utilizing periodic potentials. This is analogous to the technique of dispersion management known in photon optics. Matter wave packets are realized by Bose-Einstein condensates of 87Rb in an optical dipole potential acting as a one-dimensional waveguide. A weak optical lattice is used to control the dispersion relation of the matter waves during the propagation of the wave packets. The dynamics are observed in position space and interpreted using the concept of effective mass. By switching from positive to negative effective mass, the dynamics can be reversed. The breakdown of the approximation of constant, as well as experimental signatures of an infinite effective mass are studied.     

The physical meaning of Fermi coordinates

Fermi coordinates (FC) are supposed to be the natural extension of Cartesian coordinates for an arbitrary moving observer in curved space-time. Since their construction cannot be done on the whole space or even in the whole past of the observer we examine which construction principles are responsible for this effect and how they may be modified. A proposal for a modification is made and applied to the observer with constant acceleration in the two- and four-dimensional Minkowski space. The two-dimensional case shows some surprising similarities to Kruskal space which generalize those found by Rindler for the outer region of Kruskal space and the Rindler wedge. In perturbational approaches the modification also leads to different predictions for certain physical systems. As an example we consider atomic interferometry and derive the deviation of the acceleration-induced phase shift from the standard result in Fermi coordinates.     

A Click-Chemistry Linked 2′3′-cGAMP Analogue

2′3′-cGAMP is an uncanonical cyclic dinucleotide where one A and one G base are connected via a 3′-5′ and a unique 2′-5′ linkage. The molecule is produced by the cyclase cGAS in response to cytosolic DNA binding. cGAMP activates STING and hence one of the most powerful pathways of innate immunity. cGAMP analogues with uncharged linkages that feature better cellular penetrability are currently highly desired. Here, the synthesis of a cGAMP analogue with one amide and one triazole linkage is reported. The molecule is best prepared via a first Cu^I-catalyzed click reaction, which establishes the triazole, while the cyclization is achieved by macrolactamization.     

Large cross-phase modulation between slow copropagating weak pulses in 87Rb

We propose a scheme to generate double electromagnetically induced transparency and optimal cross-phase modulation for two slow, copropagating pulses with matched group velocities in a single species of atom, namely 87Rb. A single pump laser is employed and a homogeneous magnetic field is utilized to avoid cancellation effects through the nonlinear Zeeman effect. We suggest a feasible preparational procedure for the atomic initial state to achieve matched group velocities for both signal fields.     

Single-qubit optical quantum fingerprinting

We analyze and demonstrate the feasibility and superiority of linear optical single-qubit fingerprinting over its classical counterpart. For one-qubit fingerprinting of two-bit messages, we prepare "tetrahedral" qubit states experimentally and show that they meet the requirements for quantum fingerprinting to exceed the classical capability. We prove that shared entanglement permits 100% reliable quantum fingerprinting, which will outperform classical fingerprinting even with arbitrary amounts of shared randomness.     

Investigation and design of an impact actuated micro shift valve

New concepts for an impact actuated micro shift valve are presented which are useful, e.g. as implant for the hydrocephalus disease. Such an implant must fulfil requirements, such as using biocompatible materials, a separation of the actuator from the fluid, MRT safety and low-energy consumption in order to allow a battery-powered system. The concepts are based on the impacts that transmit an impulse into the interior of the valve through the casing, switching the valve. In order to predict the energy transmitted into the valve, an elastic multibody model is created, verified with full finite element simulations and experiments on scaled-up models. Using this model, the most important effects and parameters are discussed. Also, fluid effects are included into the elastic multibody model for a qualitative assessment of its influence on the efficiency. The simulations are compared to experiments performed with a scaled model for two different cases. Two designs of a shift valve based on impact actuation are built as prototypes and tested.     

Laser cooling of molecules via single spontaneous emission

A general scheme for reducing the center-of-mass entropy is proposed. It is based on the repetition of a cycle, composed of three concepts: velocity selection, deceleration and irreversible accumulation. Well-known laser techniques are used to represent these concepts: Raman π-pulse for velocity selection, STIRAP for deceleration, and a single spontaneous emission for irreversible accumulation. No closed pumping cycle nor repeated spontaneous emissions are required, so the scheme is applicable to cool a molecular gas. The quantum dynamics are analytically modelled using the density matrix. It is shown that during the coherent processes the gas is translationally cooled. The internal states serve as an entropy sink, in addition to spontaneous emission. This scheme provides new possibilities to translationally laser-cool molecules for high precision molecular spectroscopy and interferometry. Received 25 June 2002 / Received in final form 28 September 2002 Published online 12 November 2002 RID="a" ID="a"e-mail: ooi@spock.physik.uni-konstanz.de RID="b" ID="b"e-mail: Peter.Marzlin@uni-konstanz.de RID="c" ID="c"e-mail: Juergen.Audretsch@uni-konstanz.de     

Atom optics and quantum groups

It is shown that in atom optics physical systems arise which have close similarities to quantum group structures. A particular example for which an atomic operator provides a representation of the quantum group GL _q (2,C) forq=−1 is presented.