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Jun 29, 2018
06/18

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Nikolaos Perakis; Andreas M. Hein

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The main benefit of an interstellar mission is to carry out in-situ measurements within a target star system. To allow for extended in-situ measurements, the spacecraft needs to be decelerated. One of the currently most promising technologies for deceleration is the magnetic sail which uses the deflection of interstellar matter via a magnetic field to decelerate the spacecraft. However, while the magnetic sail is very efficient at high velocities, its performance decreases with lower speeds....

Topics: Popular Physics, Space Physics, Physics

Source: http://arxiv.org/abs/1603.03015

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Sep 23, 2013
09/13

by
M. Hein; W. Dür; H. -J. Briegel

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We investigate entanglement properties of multipartite states under the influence of decoherence. We show that the lifetime of (distillable) entanglement for GHZ-type superposition states decreases with the size of the system, while for a class of other states -namely all graph states with constant degree- the lifetime is independent of the system size. We show that these results are largely independent of the specific decoherence model and are in particular valid for all models which deal with...

Source: http://arxiv.org/abs/quant-ph/0408165v1

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Jun 29, 2018
06/18

by
M. Hein; R. Seemann; S. Afkhami

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A computational framework is developed to address capillary self-focusing in Step Emulsification. The microfluidic system consists of a single shallow and wide microchannel that merges into a deep reservoir. A continuum approach coupled with a volume of fluid method is used to model the capillary self-focusing effect. The original governing equations are reduced using the Hele-Shaw approximation. We show that the interface between the two fluids takes the shape of a neck narrowing in the flow...

Topics: Fluid Dynamics, Physics

Source: http://arxiv.org/abs/1604.03567

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Sep 24, 2013
09/13

by
Andrew M. Hein; Scott A. McKinley

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While microscopic organisms can use gradient-based search to locate resources, this strategy can be poorly suited to the sensory signals available to macroscopic organisms. We propose a framework that models search-decision making in cases where sensory signals are infrequent, subject to large fluctuations, and contain little directional information. Our approach simultaneously models an organism's intrinsic movement behavior (e.g. Levy walk) while allowing this behavior to be adjusted based on...

Source: http://arxiv.org/abs/1202.3384v1

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Sep 22, 2013
09/13

by
M. Hein; J. Eisert; H. J. Briegel

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Graph states are multi-particle entangled states that correspond to mathematical graphs, where the vertices of the graph take the role of quantum spin systems and edges represent Ising interactions. They are many-body spin states of distributed quantum systems that play a significant role in quantum error correction, multi-party quantum communication, and quantum computation within the framework of the one-way quantum computer. We characterize and quantify the genuine multi-particle...

Source: http://arxiv.org/abs/quant-ph/0307130v7

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Jun 30, 2018
06/18

by
M. Hein; S. Afkhami; R. Seemann; L. Kondic

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Step-emulsification is a microfluidic technique for droplet generation which relies on the abrupt decrease of confinement of a liquid filament surrounded by a continuous phase. A striking feature of this geometry is the transition between two distinct droplet breakup regimes, the "step-regime" and "jet-regime", at a critical capillary number. In the step-regime, small and monodisperse droplets break off from the filament directly at a topographic step, while in the...

Topics: Fluid Dynamics, Physics

Source: http://arxiv.org/abs/1405.5127

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Jun 29, 2018
06/18

by
Sven M. Hein; Camille Aron; Hakan E. Türeci

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Pure dephasing processes limit the fidelities achievable in driven-dissipative schemes for stabilization of entangled states of qubits. We propose a scheme which, combined with already existing entangling methods, purifies the desired entangled state by driving out of equilibrium auxiliary dissipative cavity modes coupled to the qubits. We lay out the specifics of our scheme and compute its efficiency in the particular context of two superconducting qubits in a cavity-QED architecture, where...

Topics: Mesoscale and Nanoscale Physics, Quantum Physics, Condensed Matter

Source: http://arxiv.org/abs/1604.07198

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Sep 19, 2013
09/13

by
W. Dür; M. Hein; J. I. Cirac; H. -J. Briegel

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We consider noisy, non-local unitary operations or interactions, i.e. the corresponding evolutions are described by completely positive maps or master equations of Lindblad form. We show that by random local operations the completely positive maps can be depolarized to a standard form with a reduced number of parameters describing the noise process in such a way that the noiseless (unitary) part of the evolution is not altered. A further reduction of the parameters, in many cases even to a...

Source: http://arxiv.org/abs/quant-ph/0507134v1

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Sep 21, 2013
09/13

by
W. D{ü}r; L. Hartmann; M. Hein; M. Lewenstein; H. J. Briegel

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We consider N initially disentangled spins, embedded in a ring or d-dimensional lattice of arbitrary geometry, which interact via some long--range Ising--type interaction. We investigate relations between entanglement properties of the resulting states and the distance dependence of the interaction in the limit N to infinity. We provide a sufficient condition when bipartite entanglement between blocks of L neighboring spins and the remaining system saturates, and determine S_L analytically for...

Source: http://arxiv.org/abs/quant-ph/0407075v2

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Jun 28, 2018
06/18

by
Andrew M. Hein; Douglas R. Brumley; Francesco Carrara; Roman Stocker; Simon A. Levin

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Many chemotactic bacteria inhabit environments in which chemicals appear as localized pulses and evolve by processes such as diffusion and mixing. We show that, in such environments, physical limits on the accuracy of temporal gradient sensing govern when and where bacteria can accurately measure the cues they use to navigate. Chemical pulses are surrounded by a predictable dynamic region, outside which bacterial cells cannot resolve gradients above noise. The outer boundary of this region...

Topics: Soft Condensed Matter, Condensed Matter, Biological Physics, Cell Behavior, Physics, Quantitative...

Source: http://arxiv.org/abs/1512.04217

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Sep 21, 2013
09/13

by
M. Hein; W. Dür; J. Eisert; R. Raussendorf; M. Van den Nest; H. -J. Briegel

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Graph states form a rich class of entangled states that exhibit important aspects of multi-partite entanglement. At the same time, they can be described by a number of parameters that grows only moderately with the system size. They have a variety of applications in quantum information theory, most prominently as algorithmic resources in the context of the one-way quantum computer, but also in other fields such as quantum error correction and multi-partite quantum communication, as well as in...

Source: http://arxiv.org/abs/quant-ph/0602096v1