4,287 research outputs found

    Superfluidity and Stabilities of a Bose-Einstein condensate with periodically modulated interatomic interaction

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    We study theoretically the superfluidity and stability of a Bose-Einstein condensate (BEC) whose interatomic scattering length is periodically modulated with optical Feshbach resonance. Our numerical study finds that the properties of this periodic BEC are strongly influenced by the modulation strength. When the modulation strength is small, only the Bloch waves close to the Brillouin zone edge suffer both Landau and dynamical instabilities. When the modulation strength is strong enough, all Bloch waves become dynamically unstable. In other words, the periodic BEC loses its superfluidity completely.Comment: 5 pages, 5 figure

    Quantum phase transition of Bose-Einstein condensates on a ring nonlinear lattice

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    We study the phase transitions in a one dimensional Bose-Einstein condensate on a ring whose atomic scattering length is modulated periodically along the ring. By using a modified Bogoliubov method to treat such a nonlinear lattice in the mean field approximation, we find that the phase transitions are of different orders when the modulation period is 2 and greater than 2. We further perform a full quantum mechanical treatment based on the time-evolving block decimation algorithm which confirms the mean field results and reveals interesting quantum behavior of the system. Our studies yield important knowledge of competing mechanisms behind the phase transitions and the quantum nature of this system.Comment: 12 pages, 7 figure

    Tunable interfaces for realizing universal quantum computation with topological qubits

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    We propose to implement tunable interfaces for realizing universal quantum computation with topological qubits. One interface is between the topological and superconducting qubits, which can realize arbitrary single-qubit gate on the topological qubit. When two qubits are involved, the interface between the topological qubits and a microwave cavity can induce a nontrivial two-qubit gate, which can not be constructed based on braiding operations. The two interfaces, being tunable via an external magnetic flux, may serve as the building blocks towards universal quantum computation with topological qubits

    Both adhE and a Separate NADPH-Dependent Alcohol Dehydrogenase Gene, adhA, Are Necessary for High Ethanol Production in Thermoanaerobacterium saccharolyticum

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    Thermoanaerobacterium saccharolyticum has been engineered to produce ethanol at ∼90% theoretical yield and titer of 70 g/L. Its ethanol-producing ability has drawn attention to its metabolic pathways, which could potentially be transferred to other organisms of interest. Here we report that the iron-containing AdhA is important for ethanol production in the high-ethanol strain of T. saccharolyticum (LL1049). A single-gene deletion of adhA in LL1049 reduced ethanol production by ∼50%, whereas multiple gene deletions of all annotated alcohol dehydrogenases except adhA and adhE did not affect ethanol production. Deletion of adhA in wild-type T. saccharolyticum reduced NADPH-linked ADH activity (acetaldehyde-reducing) by 93%
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