135 research outputs found
Teleportation in a noisy environment: a quantum trajectories approach
We study the fidelity of quantum teleportation for the situation in which
quantum logic gates are used to provide the long distance entanglement required
in the protocol, and where the effect of a noisy environment is modeled by
means of a generalized amplitude damping channel. Our results demonstrate the
effectiveness of the quantum trajectories approach, which allows the simulation
of open systems with a large number of qubits (up to 24). This shows that the
method is suitable for modeling quantum information protocols in realistic
environments.Comment: 9 pages, 2 figure
Drop impact dynamics on slippery liquid-infused porous surfaces: influence of oil thickness
Slippery liquid-infused porous surfaces (SLIPS) are porous nanostructures
impregnated with a low surface tension lubricant. They have recently shown
great promise in various applications that require non-wettable
superhydrophobic surfaces. In this paper, we investigate experimentally the
influence of the oil thickness on the wetting properties and drop impact
dynamics of new SLIPS. By tuning the thickness of the oil layer deposited
through spin-coating, we show that a sufficiently thick layer of oil is
necessary to avoid dewetting spots on the porous nanostructure and thus
increasing the homogeneity of the liquid distribution. Drop impact on these
surfaces is investigated with a particular emphasis on the spreading and
rebound dynamics when varying the oil thickness and the Weber number
Quantum teleportation by particle-hole annihilation in the Fermi sea
A tunnel barrier in a degenerate electron gas was recently discovered as a
source of entangled particle-hole excitations. The entanglement is produced by
elastic tunneling events, without requiring electron-electron interactions.
Here we investigate the inverse process, the annihilation of an electron and a
hole by elastic scattering. We find that this process leads to teleportation of
the (unknown) state of the annihilated electron to a second, distant electron
-- if the latter was previously entangled with the annihilated hole. We propose
an experiment, involving low-frequency noise measurements on a two-dimensional
electron gas in a high magnetic field, to detect teleportation of electrons and
holes in the two lowest Landau levels.Comment: 5 pages including 2 figures; [2017: fixed broken postscript figures
Spin noise and Bell inequalities in a realistic superconductor-quantum dot entangler
Charge and spin current correlations are analyzed in a source of
spin-entangled electrons built from a superconductor and two quantum dots in
parallel. In addition to the ideal (crossed Andreev) channel, parasitic
channels (direct Andreev and cotunneling) and spin flip processes are fully
described in a density matrix framework. The way they reduce both the
efficiency and the fidelity of the entangler is quantitatively described by
analyzing the zero-frequency noise correlations of charge current as well as
spin current in the two output branches. Spin current noise is characterized by
a spin Fano factor, equal to 0 (total current noise) and -1 (crossed
correlations) for an ideal entangler. The violation of the Bell inequalities,
as a test of non-locality (entanglement) of split pairs, is formulated in terms
of the correlations of electron charge and spin numbers counted in a specific
time window . The efficiency of the test is analyzed, comparing to
the various time scales in the entangler operation.Comment: 8 pages, 5 figures, references added, to appear in Phys. Rev.
Clogging by sieving in microchannels: Application to the detection of contaminants in colloidal suspensions
We report on a microfluidic method that allows measurement of a small
concentration of large contaminants in suspensions of solid micrometer-scale
particles. To perform the measurement, we flow the colloidal suspension through
a series of constrictions, i.e. a microchannel of varying cross-section. We
show and quantify the role of large contaminants in the formation of clogs at a
constriction and the growth of the resulting filter cake. By measuring the time
interval between two clogging events in an array of parallel microchannels, we
are able to estimate the concentration of contaminants whose size is selected
by the geometry of the microfluidic device. This technique for characterizing
colloidal suspensions offers a versatile and rapid tool to explore the role of
contaminants on the properties of the suspensions
Experimental study of libration-driven zonal flows in non-axisymmetric containers
International audienceOrbital dynamics that lead to longitudinal libration of celestial bodies also result in an elliptically deformed equatorial core-mantle boundary. The non-axisymmetry of the boundary leads to a topographic coupling between the assumed rigidmantle and the underlying low viscosity fluid.The present experimental study investigates theeffect of non axisymmetric boundaries on the zonal flow driven by longitudinal libration. For large enough equatorial ellipticity, we report intermittent space-filling turbulence in particular bands of resonant frequency correlated with larger amplitude zonal flow. The mechanism underlying the intermittent turbulence has yet to be unambiguously determined. Nevertheless, recent numerical simulations in triaxial and biaxial ellipsoids suggest that it may be associated with the growth and collapse of an elliptical instability (Cebron et al., 2012). Outside of the band of resonance, we find that the background flow is laminar and the zonal flow becomes independent of the geometry at first order, in agreement with a non linear mechanism in the Ekman boundary layer (e.g. Calkins et al.; 2010, Sauret and Le Dizes, 2012b)
Spin current shot noise as a probe of interactions in mesoscopic systems
It is shown that the spin resolved current shot noise can probe attractive or
repulsive interactions in mesoscopic systems. This is illustrated in two
physical situations : i) a normal-superconducting junction where the spin
current noise is found to be zero, and ii) a single electron transistor (SET),
where the spin current noise is found to be Poissonian. Repulsive interactions
may also lead to weak attractive correlations (bunching of opposite spins) in
conditions far from equilibrium. Spin current shot noise can be used to measure
the spin relaxation time , and a set-up is proposed in a quantum dot
geometry.Comment: 5 pages, 4 Figures, revised version, added reference
Characterization of oligomers from methylglyoxal under dark conditions : a pathway to produce secondary organic aerosol through cloud processing during nighttime
Aqueous-phase oligomer formation from methylglyoxal, a major atmospheric photooxidation product, has been investigated in a simulated cloud matrix under dark conditions. The aim of this study was to explore an additional pathway producing secondary organic aerosol (SOA) through cloud processes without participation of photochemistry during nighttime. Indeed, atmospheric models still underestimate SOA formation, as field measurements have revealed more SOA than predicted. Soluble oligomers (n = 1-8) formed in the course of acid-catalyzed aldol condensation and acid-catalyzed hydration followed by acetal formation have been detected and characterized by positive and negative ion electrospray ionization mass spectrometry. Aldol condensation proved to be a favorable mechanism under simulated cloud conditions, while hydration/acetal formation was found to strongly depend on the pH of the system and only occurred at a pH < 3.5. No evidence was found for formation of organosulfates. The aldol oligomer series starts with a beta-hydroxy ketone via aldol condensation, where oligomers are formed by multiple additions of C3H4O2 units (72 Da) to the parent beta-hydroxy ketone. Ion trap mass spectrometry experiments were performed to structurally characterize the major oligomer species. A mechanistic pathway for the growth of oligomers under cloud conditions and in the absence of UV-light and OH radicals, which could substantially enhance in-cloud SOA yields, is proposed here for the first time
Mechanical tuning of the evaporation rate of liquid on crossed fibers
We investigate experimentally the drying of a small volume of perfectly
wetting liquid on two crossed fibers. We characterize the drying dynamics for
the three liquid morphologies that are encountered in this geometry: drop,
column and a mixed morphology, in which a drop and a column coexist. For each
morphology, we rationalize our findings with theoretical models that capture
the drying kinetics. We find that the evaporation rate depends significantly on
the liquid morphology and that the drying of liquid column is faster than the
evaporation of the drop and the mixed morphology for a given liquid volume.
Finally, we illustrate that shearing a network of fibers reduces the angle
between them, changes the morphology towards the column state, and so enhances
the drying rate of a volatile liquid deposited on it
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