479 research outputs found
Effect of noisy channels on the transmission of mesoscopic twin-beam states
Quantum properties of light, which are crucial resources for quantum technologies, are quite fragile in nature and can be degraded and even concealed by the environment. We show, both theoretically and experimentally, that mesoscopic twin-beam states of light can preserve their nonclassicality even in the presence of major losses and different types of noise, thus suggesting their potential usefulness to encode information in quantum communication protocols. We develop a comprehensive general analytical model for a measurable nonclassicality criterion and find thresholds on noise and losses for the survival of entanglement in the twin beam
Reliable source of conditional non-Gaussian states from single-mode thermal fields
We address both theoretically and experimentally the generation of pulsed
non-Gaussian states from classical Gaussian ones by means of conditional
measurements. The setup relies on a beam splitter and a pair of linear
photodetectors able to resolve up to tens of photons in the two outputs. We
show the reliability of the setup and the good agreement with the theory for a
single-mode thermal field entering the beam splitter and present a thorough
characterization of the photon statistics of the conditional states.Comment: 18 pages, 12 figure
Self-consistent characterization of light statistics
We demonstrate the possibility of a self-consistent characterization of the
photon-number statistics of a light field by using photoemissive detectors with
internal gain simply endowed with linear input/output responses. The method can
be applied to both microscopic and mesoscopic photon-number regimes. The
detectors must operate in the linear range without need of photon-counting
capabilities.Comment: To be published in "Journal of Modern Optics
Special issue on basics and applications in quantum optics
Quantum technologies are advancing very rapidly and have the potential to innovate communication and computing far beyond current possibilities. Among the possible plat- forms suitable to run quantum technology protocols, in the last decades quantum optics has received a lot of attention for the handiness and versatility of optical systems. In addition to studying the fundamentals of quantum mechanics, quantum optical states have been exploited for several applications, such as quantum-state engineering, quantum communication and quantum cryptography protocols, enhanced metrology and sensing, quantum optical integrated circuits, quantum imaging, and quantum biological effects. In this Special Issue, we collect some papers and also a review on some recent research activities that show the potential of quantum optics for the advancement of quantum technologies
Conditional measurements on multimode pairwise entangled states from spontaneous parametric downconversion
We address the intrinsic multimode nature of the quantum state of light
obtained by pulsed spontaneous parametric downconversion and develop a
theoretical model based only on experimentally accessible quantities. We
exploit the pairwise entanglement as a resource for conditional multimode
measurements and derive closed formulas for the detection probability and the
density matrix of the conditional states. We present a set of experiments
performed to validate our model in different conditions that are in excellent
agreement with experimental data. Finally, we evaluate nonGaussianity of the
conditional states obtained from our source with the aim of discussing the
effects of the different experimental parameters on the efficacy of this type
of conditional state preparation
Robust generation of entanglement in Bose-Einstein condensates by collective atomic recoil
We address the dynamics induced by collective atomic recoil in a
Bose-Einstein condensate in presence of radiation losses and atomic
decoherence. In particular, we focus on the linear regime of the lasing
mechanism, and analyze the effects of losses and decoherence on the generation
of entanglement. The dynamics is that of three bosons, two atomic modes
interacting with a single-mode radiation field, coupled with a bath of
oscillators. The resulting three-mode dissipative Master equation is solved
analytically in terms of the Wigner function. We examine in details the two
complementary limits of {\em high-Q cavity} and {\em bad-cavity}, the latter
corresponding to the so-called superradiant regime, both in the quasi-classical
and quantum regimes. We found that three-mode entanglement as well as two-mode
atom-atom and atom-radiation entanglement is generally robust against losses
and decoherence,thus making the present system a good candidate for the
experimental observation of entanglement in condensate systems. In particular,
steady-state entanglement may be obtained both between atoms with opposite
momenta and between atoms and photons
State reconstruction by on/off measurements
We demonstrate a state reconstruction technique which provides either the
Wigner function or the density matrix of a field mode and requires only
avalanche photodetectors, without any phase or amplitude discrimination power.
It represents an alternative, of simpler implementation, to quantum homodyne
tomography.Comment: 6 pages, 4 figures, revised and enlarged versio
Experimental joint signal-idler quasi-distributions and photon-number statistics for mesoscopic twin beams
Joint signal-idler photoelectron distributions of twin beams containing
several tens of photons per mode have been measured recently. Exploiting a
microscopic quantum theory for joint quasi-distributions in parametric
down-conversion developed earlier we characterize properties of twin beams in
terms of quasi-distributions using experimental data. Negative values as well
as oscillating behaviour in quantum region are characteristic for the
subsequently determined joint signal-idler quasi-distributions of integrated
intensities. Also the conditional and difference photon-number distributions
are shown to be sub-Poissonian and sub-shot-noise, respectively.Comment: 7 pages, 6 figure
Orbital medial wall fractures: Purely endoscopic endonasal repair with polyethylene implants
Our technique couples the stronger support granted by non-resorbable materials and the minimal invasiveness of the endoscopic approach without the need for long-term nasal packing
Spatial auction markets with unique consumer price
We consider a collection of auctions representing zonal electricity markets, which are joined by transmission lines in a spatial system. At each market, generating companies (traders) and customers (buyers) submit their fixed offer/bid prices together with maximal offer/bid volumes, respectively. In addition to the usual balance and capacity constraints, we consider also the additional requirement of utilizing the minimal unique purchase price for all the zones. As a result, we obtain spatial equilibrium type problems with special parameter for finding zonal prices and offer/bid volumes. We show that the streamlined formulation can be inconsistent under rather natural assumptions and propose a relaxed formulation. This problem admits suitable solution methods. We propose a parametric method combined with a bisection type procedure to solve this problem.© 2011 by Nova Science Publishers, Inc. All rights reserved
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