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Subject: search.filters.subject.530Institute: search.filters.UBSInstitut.5. Physikalisches InstitutInstitute: search.filters.UBSInstitut.Fakultätsübergreifend / Sonstige EinrichtungPublication Type: search.filters.UBSTyp.ZeitschriftenartikelEnd date: 2020

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Now showing 1 - 5 of 5
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    Vibrational quenching of weakly bound cold molecular ions immersed in their parent gas
    (2020) Jachymski, Krzysztof; Meinert, Florian
    Hybrid ion–atom systems provide an excellent platform for studies of state-resolved quantum chemistry at low temperatures, where quantum effects may be prevalent. Here we study theoretically the process of vibrational relaxation of an initially weakly bound molecular ion due to collisions with the background gas atoms. We show that this inelastic process is governed by the universal long-range part of the interaction potential, which allows for using simplified model potentials applicable to multiple atomic species. The product distribution after the collision can be estimated by making use of the distorted wave Born approximation. We find that the inelastic collisions lead predominantly to small changes in the binding energy of the molecular ion.
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    Imaging single Rydberg electrons in a Bose-Einstein condensate
    (2015) Karpiuk, Tomasz; Brewczyk, Mirosław; Rzążewski, Kazimierz; Gaj, Anita; Balewski, Jonathan B.; Krupp, Alexander T.; Schlagmüller, Michael; Löw, Robert; Hofferberth, Sebastian; Pfau, Tilman
    The quantum mechanical states of electrons in atoms and molecules are distinct orbitals, which are fundamental for our understanding of atoms, molecules and solids. Electronic orbitals determine a wide range of basic atomic properties, allowing also for the explanation of many chemical processes. Here, we propose a novel technique to optically image the shape of electron orbitals of neutral atoms using electron-phonon coupling in a Bose-Einstein condensate. To validate our model we carefully analyze the impact of a single Rydberg electron onto a condensate and compare the results to experimental data. Our scheme requires only well-established experimental techniques that are readily available and allows for the direct capture of textbook-like spatial images of single electronic orbitals in a single shot experiment.
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    Coupling thermal atomic vapor to an integrated ring resonator
    (2016) Ritter, Ralf; Gruhler, Nico; Pernice, Wolfram; Kübler, Harald; Pfau, Tilman; Löw, Robert
    Strongly interacting atom-cavity systems within a network with many nodes constitute a possible realization for a quantum internet which allows for quantum communication and computation on the same platform. To implement such large-scale quantum networks, nanophotonic resonators are promising candidates because they can be scalably fabricated and interconnected with waveguides and optical fibers. By integrating arrays of ring resonators into a vapor cell we show that thermal rubidium atoms above room temperature can be coupled to photonic cavities as building blocks for chip-scale hybrid circuits. Although strong coupling is not yet achieved in this first realization, our approach provides a key step towards miniaturization and scalability of atom-cavity systems.
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    Preparation of ordered states in ultra-cold gases using Bayesian optimization
    (2020) Mukherjee, Rick; Sauvage, Frédéric; Xie, Harry; Löw, Robert; Mintert, Florian
    Ultra-cold atomic gases are unique in terms of the degree of controllability, both for internal and external degrees of freedom. This makes it possible to use them for the study of complex quantum many-body phenomena. However in many scenarios, the prerequisite condition of faithfully preparing a desired quantum state despite decoherence and system imperfections is not always adequately met. To pave the way to a specific target state, we implement quantum optimal control based on Bayesian optimization. The probabilistic modeling and broad exploration aspects of Bayesian optimization are particularly suitable for quantum experiments where data acquisition can be expensive. Using numerical simulations for the superfluid to Mott-insulator transition for bosons in a lattice as well as for the formation of Rydberg crystals as explicit examples, we demonstrate that Bayesian optimization is capable of finding better control solutions with regards to finite and noisy data compared to existing methods of optimal control.
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    Double light-cone dynamics establish thermal states in integrable 1D Bose gases
    (2018) Langen, Tim; Schweigler, Thomas; Demler, Eugene; Schmiedmayer, Joerg
    We theoretically investigate the non-equilibrium dynamics in a quenched pair of one-dimensional Bose gases with density imbalance. We describe the system using its low-energy effective theory, the Luttinger liquid model. In this framework the system shows strictly integrable relaxation dynamics via dephasing of its approximate many-body eigenstates. In the balanced case, this leads to the well-known light-cone-like establishment of a prethermalized state, which can be described by a generalized Gibbs ensemble. In the imbalanced case the integrable dephasing leads to a state that, counter-intuitively, closely resembles a thermal equilibrium state. The approach to this state is characterized by two separate light-cone dynamics with distinct characteristic velocities. This behavior is a result of the fact that in the imbalanced case observables are not aligned with the conserved quantities of the integrable system. We discuss a concrete experimental realization to study this effect using matterwave interferometry and many-body revivals on an atom chip.