| dc.description.abstract | The Dissertation Quantumness of Gaussian and non-Gaussian states in the op-
tical domain collects my personal both theoretical and experimental contribu-
tions, in the context of the Quantum Information theory in continuous variables
(cv). In this context, the research focused on the analysis of the quantum prop-
erties of bipartite states of electromagnetic radiation.
The Dissertation contains, rst, the study of the main possible quantum cor-
relations between two modes of the electromagnetic eld. Particular attention
has been devoted to the analysis of the di¤erent forms of non-locality present
in quantum mechanics. Second, it shows the analysis of how the presence of
quantum properties in bipartite states a¤ects the performance of these states,
when they are used as resources in quantum protocols. In particular, the cv
teleportation protocol was used as a reference to test the goodness of results.
The quantum resources can be divided in two main classes: Gaussian re-
sources and non-Gaussian ones. My research activity has been strucured in
which way to be able to proceed, in parallel, to the analysis of both classes.
Gaussian resoures.To assess the presence of entanglement in a quantum
system it is possible to refer to the many criteria proposed in the literature. In
the Dissertation it is reported the study of some main criteria generally used
for Gaussian bipartite mixed states. This study has allowed us to establish a
hierarchy very useful for the evaluation of the entanglement. Then we have dis-
cussed and experimentally analyzed the e¤ects of the transmission over a lossy
channel on the quantumness of bipartite Gaussian states, focusing our analysis
on the states generated by a type-II optical parametric oscillator (OPO). Even-
tually it is reported the study of the Bell s inequality in terms of purity and
entanglement for a bipartite Gaussian state, desribed by a symmetric covari-
ance matrix..It allows to investigate how the "quantumness" owned by a state,
established by the violation of Bell s inequality, is related to the purity of the
state and to the entanglement.
Non-Gaussian resources. The study of non-Gaussian resources is mainly
related to a particular class of states: the squeezed Bell states. All the analy-
sis carried out to date show that these states are one of the best possible re-
sources for e¢ cient BKV quantum teleportation protocol. This is con rmed by
two additional theoretical tests presented in the Dissertation. In fact, squeezed
Bell states maximize the violation of Bell s inequality with respect to all other
(Gaussian and non-Gaussian) states obtained from the same class. So they
represent the most non-local resource among all those considered (for example,
the squeezed photon number states, the photon subtracted squeezed states, the
photon added states, the squeezed vacuum states). Moreover, as demonstrated
in the course of the Dissertation, squeezed Bell states are the best resource for
teleportation of a coherent state, even after having undergone a process of en-
tanglement swapping. The result is compared with that provided by the other
main quantum swapped resources of the same class. As a consequence of the
positive results obtained from the tests, it was designed a scheme that allows
the experimental production of squeezed Bell states. It is then evaluated its
experimental feasibility both in ideal and realistic conditions obtaining very
encouraging results. Finally, it is dealt the study (it is at a very preliminary
stage) of a non-Gaussian state produced by a sub-threshold OPO, when there
are uctuations of some parameters of the optical device (amplitude and phase
of the pump, etc..) at the aim to nd a new strategy for the generation of
non-Gaussian resources. [edited by author] | en_US |
