13,271 research outputs found
Normal form decomposition for Gaussian-to-Gaussian superoperators
In this paper we explore the set of linear maps sending the set of quantum
Gaussian states into itself. These maps are in general not positive, a feature
which can be exploited as a test to check whether a given quantum state belongs
to the convex hull of Gaussian states (if one of the considered maps sends it
into a non positive operator, the above state is certified not to belong to the
set). Generalizing a result known to be valid under the assumption of complete
positivity, we provide a characterization of these Gaussian-to-Gaussian (not
necessarily positive) superoperators in terms of their action on the
characteristic function of the inputs. For the special case of one-mode
mappings we also show that any Gaussian-to-Gaussian superoperator can be
expressed as a concatenation of a phase-space dilatation, followed by the
action of a completely positive Gaussian channel, possibly composed with a
transposition. While a similar decomposition is shown to fail in the multi-mode
scenario, we prove that it still holds at least under the further hypothesis of
homogeneous action on the covariance matrix
Influence of electromagnetic interferences on the gravimetric sensitivity of surface acoustic waveguides
Surface acoustic waveguides are increasing in interest for (bio)chemical
detection. The surface mass modification leads to measurable changes in the
propagation properties of the waveguide. Among a wide variety of waveguides,
Love mode has been investigated because of its high gravimetric sensitivity.
The acoustic signal launched and detected in the waveguide by electrical
transducers is accompanied by an electromagnetic wave; the interaction of the
two signals, easily enhanced by the open structure of the sensor, creates
interference patterns in the transfer function of the sensor. The influence of
these interferences on the gravimetric sensitivity is presented, whereby the
structure of the entire sensor is modelled. We show that electromagnetic
interferences generate an error in the experimental value of the sensitivity.
This error is different for the open and the closed loop configurations of the
sensor. The theoretical approach is completed by the experimentation of an
actual Love mode sensor operated under liquid in open loop configuration. The
experiment indicates that the interaction depends on the frequency and the mass
modifications.Comment: 28 pages, 8 figure
Influence of cane girdling and plastic covering on leaf gas exchange, water potential and viticultural performance of table grape cv. Matilde
Canes of field-grown uncovered and covered (plastic film) table grapes, cv. Matilde, were girdled at veraison. Leaves of girdled vines displayed lower rates of transpiration on a leaf area basis and lower rates of CO2 uptake; stem and leaf water potentials were decreased. Both, covering and cane girdling stimulated vegetative growth and increased leaf area per vine. However, sugar accumulation in berries and fruit quality were not affected by cane girdling and were slightly reduced by covering. Therefore, harvesting dates were not advanced. Cane girdling appeared to influence carbohydrate partitioning by stimulating shoot growth at the expense of fruit production. It is concluded that the stage of rapid sugar accumulation was not yet reached by the time girdling took place. The development of a larger transpiring leaf surface area per vine is supposed to have lowered the vine water status
Entanglement detection in hybrid optomechanical systems
We study a device formed by a Bose Einstein condensate (BEC) coupled to the
field of a cavity with a moving end-mirror and find a working point such that
the mirror-light entanglement is reproduced by the BEC-light quantum
correlations. This provides an experimentally viable tool for inferring
mirror-light entanglement with only a limited set of assumptions. We prove the
existence of tripartite entanglement in the hybrid device, persisting up to
temperatures of a few milli-Kelvin, and discuss a scheme to detect it.Comment: 6 pages, 7 figures, published versio
Reduction of Evapotranspiration in Microenvironment Conditions of Table Grape Vineyards Protected by Different Types of Plastic Covers
Simultaneous surface acoustic wave and surface plasmon resonance measurements: electrodeposition and biological interactions monitoring
We present results from an instrument combining surface acoustic wave (SAW)
propagation and surface plasmon resonance (SPR) measurements. The objective is
to use two independent methods, the former based on adsorbed mass change
measurements and the latter on surface dielectric properties variations, to
identify physical properties of protein layers, and more specifically their
water content. We display mass sensitivity calibration curves using
electrodeposition of copper leading to a sensitivity in liquid of 150
for the Love mode device used here, and the application to monitoring
biological processes. The extraction of protein layer thickness and protein to
water content ratio is also presented for S-layer proteins under investigation.
We obtain respectively 4.70.7 nm and 7515%.Comment: 13 pages, 4 figure
Cavity-aided quantum parameter estimation in a bosonic double-well Josephson junction
We describe an apparatus designed to make non-demolition measurements on a
Bose-Einstein condensate (BEC) trapped in a double-well optical cavity. This
apparatus contains, as well as the bosonic gas and the trap, an optical cavity.
We show how the interaction between the light and the atoms, under appropriate
conditions, can allow for a weakly disturbing yet highly precise measurement of
the population imbalance between the two wells and its variance. We show that
the setting is well suited for the implementation of quantum-limited estimation
strategies for the inference of the key parameters defining the evolution of
the atomic system and based on measurements performed on the cavity field. This
would enable {\it de facto} Hamiltonian diagnosis via a highly controllable
quantum probe.Comment: 8 pages, 5 figures, RevTeX4; Accepted for publication in Phys. Rev.
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