323,086 research outputs found
Un'applicazione della teoria dei semigruppi ordinati nell'ambito della teoria delle decisioni
No full textIn this paper we introduce in the semigroup S, whose elements are to be evalued in terms of preference in a particular situation, a pre-order defined through semigroups of S. Then this pre-order is a preference relation with transitive indifference, which can be represented by a utility function
Experimental quantification of non-Gaussianity of phase-randomized coherent states
No full textWe present the experimental investigation of the non-Gaussian nature of some mixtures of Fock states by reconstructing their Wigner function and exploiting two recently introduced measures of non-Gaussianity. In particular, we demonstrate the consistency between the di®erent approaches and the monotonicity of the two measures for states belonging to the class of phase- randomized coherent states. Moreover, we prove that the exact behavior of one measure with respect to the other depends on the states under investigation and devise possible criteria to discriminate which measure is more useful for the characterization of the states in realistic applications
Gaussian and Non-Gaussian operations on non-Gaussian state: engineering non-Gaussianity
No full textMultiple photon subtraction applied to a displaced phase-averaged coherent state, which is a non-Gaussian classical state, produces conditional states with a non trivial (positive) Glauber-Sudarshan P-representation. We theoretically and experimentally demonstrate that, despite its simplicity, this class of conditional states cannot be fully characterized by direct detection of photon numbers. In particular, the non-Gaussianity of the state is a characteristics that must be assessed by phase-sensitive measurements. We also show that the non-Gaussianity of conditional states can be manipulated by choosing suitable conditioning values and composition of phase-averaged states
Measuring high-order photon-number correlations in experiments with multimode pulsed quantum states
No full textWe implement a direct detection scheme based on hybrid photodetectors to experimentally investigate high- order correlations for detected photons by means of experimentally accessible quantities. The scheme is self- consistent, allowing the estimation of all the involved parameters (quantum efficiency, number of modes, and average energy). In particular, we show how high-order correlation functions can be exploited to fully characterize bipartite multimode states in regimes realistic for quantum technology, that is, in the mesoscopic photon-number domain and with limited quantum efficiency. Furthermore, we introduce a nonclassicality criterion based on a simple linear combination of high-order correlation functions
Manipulating the non-Gaussianity of phase-randomized coherent states
No full textWe experimentally investigate the non-Gaussian features of the phase-randomized coherent states, a class of states exploited in communica- tion channels and in decoy state-based quantum key distribution protocols. In particular, we reconstruct their phase-insensitive Wigner functions and quantify their non-Gaussianity. The measurements are performed in the mesoscopic photon-number domain by means of a direct detection scheme involving linear detectors
High-order photon-number correlations: a resource for characterization and applications of quantum states
No full textWe measure high-order correlation functions of detected-photon numbers in the mesoscopic regime by means of hybrid photodetectors. The analytical expressions for correlations are evaluated in terms of quantities that can be experimentally accessed by a selfconsistent analysis of the detectors' outputs. We demonstrate that high-order correlations can be used to charac- terize the nature of the optical states, for instance by better discriminating between classical and quantum behavior even in critical situations, such as multimode twin-beam state. The results are in very good agreement with the theory, both for classical states and quantum states
Bracket states for communication protocols with coherent states
No full textWe present the generation and characterization of the class of bracket states, namely phase-sensitive mixtures of coherent states exhibiting symmetry properties in the phase-space de- scription. A bracket state can be seen as the statistical ensemble arriving at a receiver in a typical coherent-state-based communication channel. We show that when a bracket state is mixed at a beam splitter with a local oscillator, both the emerging beams exhibit a Fano factor larger than 1 and dependent on the relative phase between the input state and the local oscil- lator. We discuss the possibility to exploit this dependence to monitor the phase difference for the enhancement of the performances of a simple communication scheme based on direct detection. Our experimental setup involves linear optical elements and a pair of photon-number- resolving detectors operated in the mesoscopic photon-number domain
On the role of the local oscillator intensity in optical homodyne-like tomography
No full textIn a recent research (Olivares et al., 2019 [18]) we have demonstrated that a homodyne-like scheme, exploiting a “low-intensity” local oscillator, can be used to perform optical state tomography of both quantum and classical states of light. The reconstruction method directly uses the homodyne-like probability distribution retrieved from the detector. Here, we further investigate the role played by the local oscillator in this respect. In particular, we study to some extent how its intensity affects the quantum-state reconstruction procedure by focusing on the case of the Fock states |1〉 and |2〉, whose homodyne-like probability distributions are sensibly affected by the actual value of the LO intensity. The analysis is performed on Monte Carlo simulated experiments taking also into account the quantum detection efficiency
A convenient two step transformation of tyrosine into the antihypertensive amino acid (S)-4-hydroxy-3-hydroxymethylphenylalanine
No full textTreatment of tyrosine with paraformaldehyde and catalytic amounts of p-toluenesulfonic acid, at reflux in toluene, directly generates benzyl (S)-4-(4H-1,3-benzodioxin-6-ylmethyl)-5-oxo-1,3-oxazolane-3-carboxylate, which on treatment with boron trichloride in dichloromethane, affords (S)-4-hydroxy-3-hydroxymethylphenylalanine
Statistical characterization of discrete amplitude-modulated coherent states at telecom wavelengths by means of an up-conversion-based photon-number-resolving detector
No full textThe successful implementation of quantum communication protocols relies on the proper encoding of information in the degrees of freedom of the employed optical states. Particular interest is devoted to amplitude-phase-shift keying coherent states, which can provide robust solutions in satellite communication systems and guarantee high values of channel capacity. In this work, we implement a sum-frequency-based photon-number-resolving detector, capable of revealing discrete amplitude modulation of coherent states produced at telecom wavelengths. The detection is performed in the visible spectral range and in the photon-number-resolving domain, thus encouraging the use of more complex alphabets in which both amplitude and phase vary
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