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

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$\pm15$ $cm^2/g$ 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 4.7$\pm$0.7 nm and 75$\pm$15%.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.