674 research outputs found
Experimental pre-assessing entanglement in Gaussian states mixing
We suggest and demonstrate a method to assess entanglement generation schemes
based on mixing of Gaussian states at a beam splitter (BS). Our method is based
on the fidelity criterion and represents a tool to analyze the effect of losses
and noise before the BS in both symmetric and asymmetric channels with and
without thermal effects. More generally, our scheme allows one to pre-assess
entanglement resources and to optimize the design of BS-based schemes for the
generation of continuous variable entanglement.Comment: 10 pages, 15 figure
Tunable non-Gaussian resources for continuous-variable quantum technologies
We introduce and discuss a set of tunable two-mode states of
continuous-variable systems, as well as an efficient scheme for their
experimental generation. This novel class of tunable entangled resources is
defined by a general ansatz depending on two experimentally adjustable
parameters. It is very ample and flexible as it encompasses Gaussian as well as
non-Gaussian states. The latter include, among others, known states such as
squeezed number states and de-Gaussified photon-added and photon-subtracted
squeezed states, the latter being the most efficient non-Gaussian resources
currently available in the laboratory. Moreover, it contains the classes of
squeezed Bell states and even more general non-Gaussian resources that can be
optimized according to the specific quantum technological task that needs to be
realized. The proposed experimental scheme exploits linear optical operations
and photon detections performed on a pair of uncorrelated two--mode Gaussian
squeezed states. The desired non-Gaussian state is then realized via ancillary
squeezing and conditioning. Two independent, freely tunable experimental
parameters can be exploited to generate different states and to optimize the
performance in implementing a given quantum protocol. As a concrete instance,
we analyze in detail the performance of different states considered as
resources for the realization of quantum teleportation in realistic conditions.
For the fidelity of teleportation of an unknown coherent state, we show that
the resources associated to the optimized parameters outperform, in a
significant range of experimental values, both Gaussian twin beams and
photon-subtracted squeezed states.Comment: 13 pages, 7 figure
Full characterization of Gaussian bipartite entangled states by a single homodyne detector
We present the full experimental reconstruction of Gaussian entangled states
generated by a type--II optical parametric oscillator (OPO) below threshold.
Our scheme provides the entire covariance matrix using a single homodyne
detector and allows for the complete characterization of bipartite Gaussian
states, including the evaluation of purity, entanglement and nonclassical
photon correlations, without a priori assumptions on the state under
investigation. Our results show that single homodyne schemes are convenient and
robust setups for the full characterization of OPO signals and represent a tool
for quantum technology based on continuous variable entanglement.Comment: 4 pages, 3 figures, slightly longer version of published PR
Dopamine: The Neuromodulator of Long-Term Synaptic Plasticity, Reward and Movement Control
Dopamine (DA) is a key neurotransmitter involved in multiple physiological functions including motor control, modulation of affective and emotional states, reward mechanisms, reinforcement of behavior, and selected higher cognitive functions. Dysfunction in dopaminergic transmission is recognized as a core alteration in several devastating neurological and psychiatric disorders, including Parkinson's disease (PD), schizophrenia, bipolar disorder, attention deficit hyperactivity disorder (ADHD) and addiction. Here we will discuss the current insights on the role of DA in motor control and reward learning mechanisms and its involvement in the modulation of synaptic dynamics through different pathways. In particular, we will consider the role of DA as neuromodulator of two forms of synaptic plasticity, known as long-term potentiation (LTP) and long-term depression (LTD) in several cortical and subcortical areas. Finally, we will delineate how the effect of DA on dendritic spines places this molecule at the interface between the motor and the cognitive systems. Specifically, we will be focusing on PD, vascular dementia, and schizophrenia
In sulfolobus solfataricus, the poly(Adp-ribose) polymerase-like thermoprotein is a multifunctional enzyme
In Sulfolobus solfataricus, Sso, the ADP-ribosylating thermozyme is known to carry both auto-and heteromodification of target proteins via short chains of ADP-ribose. Here, we provide evidence that this thermoprotein is a multifunctional enzyme, also showing ATPase activity. Electrophoretic and kinetic analyses were performed using NAD+ and ATP as substrates. The results showed that ATP is acting as a negative effector on the NAD+-dependent reaction, and is also responsible for inducing the dimerization of the thermozyme. These findings enabled us to further investigate the kinetic of ADP-ribosylation activity in the presence of ATP, and to also assay its ability to work as a substrate. Moreover, since the heteroacceptor of ADP-ribose is the sulfolobal Sso7 protein, known as an ATPase, some reconstitution experiments were set up to study the reciprocal influence of the ADP-ribosylating thermozyme and the Sso7 protein on their activities, considering also the possibility of direct enzyme/Sso7 protein interactions. This study provides new insights into the ATP-ase activity of the ADP-ribosylating thermozyme, which is able to establish stable complexes with Sso7 protein
Quantum characterization of bipartite Gaussian states
Gaussian bipartite states are basic tools for the realization of quantum
information protocols with continuous variables. Their complete
characterization is obtained by the reconstruction of the corresponding
covariance matrix. Here we describe in details and experimentally demonstrate a
robust and reliable method to fully characterize bipartite optical Gaussian
states by means of a single homodyne detector. We have successfully applied our
method to the bipartite states generated by a sub-threshold type-II optical
parametric oscillator which produces a pair of thermal cross-polarized
entangled CW frequency degenerate beams. The method provide a reliable
reconstruction of the covariance matrix and allows to retrieve all the physical
information about the state under investigation. These includes observable
quantities, as energy and squeezing, as well as non observable ones as purity,
entropy and entanglement. Our procedure also includes advanced tests for
Gaussianity of the state and, overall, represents a powerful tool to study
bipartite Gaussian state from the generation stage to the detection one
Measurement of 1323 and 1487 keV resonances in 15N({\alpha}, {\gamma})19F with the recoil separator ERNA
The origin of fluorine is a widely debated issue. Nevertheless, the
^{15}N({\alpha},{\gamma})^{19}F reaction is a common feature among the various
production channels so far proposed. Its reaction rate at relevant temperatures
is determined by a number of narrow resonances together with the DC component
and the tails of the two broad resonances at E_{c.m.} = 1323 and 1487 keV.
Measurement through the direct detection of the 19F recoil ions with the
European Recoil separator for Nuclear Astrophysics (ERNA) were performed. The
reaction was initiated by a 15N beam impinging onto a 4He windowless gas
target. The observed yield of the resonances at Ec.m. = 1323 and 1487 keV is
used to determine their widths in the {\alpha} and {\gamma} channels. We show
that a direct measurement of the cross section of the
^{15}N({\alpha},{\gamma})^{19}F reaction can be successfully obtained with the
Recoil Separator ERNA, and the widths {\Gamma}_{\gamma} and {\Gamma}_{\alpha}
of the two broad resonances have been determined. While a fair agreement is
found with earlier determination of the widths of the 1487 keV resonance, a
significant difference is found for the 1323 keV resonance {\Gamma}_{\alpha} .
The revision of the widths of the two more relevant broad resonances in the
15N({\alpha},{\gamma})19F reaction presented in this work is the first step
toward a more firm determination of the reaction rate. At present, the residual
uncertainty at the temperatures of the ^{19}F stellar nucleosynthesis is
dominated by the uncertainties affecting the Direct Capture component and the
364 keV narrow resonance, both so far investigated only through indirect
experiments.Comment: 8 pages, 11 figures. Accepted for publication in PR
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