59 research outputs found
Cooperative Authentication in Underwater Acoustic Sensor Networks
With the growing use of underwater acoustic communications (UWAC) for both
industrial and military operations, there is a need to ensure communication
security. A particular challenge is represented by underwater acoustic networks
(UWANs), which are often left unattended over long periods of time. Currently,
due to physical and performance limitations, UWAC packets rarely include
encryption, leaving the UWAN exposed to external attacks faking legitimate
messages. In this paper, we propose a new algorithm for message authentication
in a UWAN setting. We begin by observing that, due to the strong spatial
dependency of the underwater acoustic channel, an attacker can attempt to mimic
the channel associated with the legitimate transmitter only for a small set of
receivers, typically just for a single one. Taking this into account, our
scheme relies on trusted nodes that independently help a sink node in the
authentication process. For each incoming packet, the sink fuses beliefs
evaluated by the trusted nodes to reach an authentication decision. These
beliefs are based on estimated statistical channel parameters, chosen to be the
most sensitive to the transmitter-receiver displacement. Our simulation results
show accurate identification of an attacker's packet. We also report results
from a sea experiment demonstrating the effectiveness of our approach.Comment: Author version of paper accepted for publication in the IEEE
Transactions on Wireless Communication
Loss tolerant device-independent quantum key distribution: a proof of principle
We here present the rate analysis and a proof of principle realization of a
device-independent quantum key distribution (QKD) protocol requiring the lowest
detection efficiency necessary to achieve a secure key compared to
device-independent protocols known so far. The protocol is based on
non-maximally entangled state and its experimental realization has been
performed by two-photon bipartite entangled states. The improvement with
respect to protocols involving maximally entangled states has been estimated.Comment: 8 pages, 4 figure + appendi
High-Visibility Time-Bin Entanglement for Testing Chained Bell Inequalities
The violation of Bell's inequality requires a well-designed experiment to
validate the result. In experiments using energy-time and time-bin
entanglement, initially proposed by Franson in 1989, there is an intrinsic
loophole due to the high postselection. To obtain a violation in this type of
experiment, a chained Bell inequality must be used. However, the local realism
bound requires a high visibility in excess of 94.63 percent in the time-bin
entangled state. In this work, we show how such a high visibility can be
reached in order to violate a chained Bell inequality with 6, 8 and 10 terms.Comment: 8 pages, 4 figure
Interference at the Single Photon Level Along Satellite-Ground Channels
Quantum interference arising from superposition of states is a striking
evidence of the validity of Quantum Mechanics, confirmed in many experiments
and also exploited in applications. However, as for any scientific theory,
Quantum Mechanics is valid within the limits in which it has been
experimentally verified. In order to extend such limits, it is necessary to
observe quantum interference in unexplored conditions such as moving terminals
at large distance in Space. Here we experimentally demonstrate single photon
interference at a ground station due to the coherent superposition of two
temporal modes reflected by a rapidly moving satellite thousand kilometers
away. The relative speed of the satellite induces a varying modulation in the
interference pattern. The measurement of the satellite distance in real time by
laser ranging allowed us to precisely predict the instantaneous value of the
interference phase. We then observed the interference patterns with visibility
up to with three different satellites and with path length up to 5000
km. Our results attest the viability of photon temporal modes for fundamental
tests of Physics and Quantum Communications in Space.Comment: Version accepted for publication in Phys. Rev. Let
Extending Wheeler's delayed-choice experiment to Space
Gedankenexperiments have consistently played a major role in the development
of quantum theory. A paradigmatic example is Wheeler's delayed-choice
experiment, a wave-particle duality test that cannot be fully understood using
only classical concepts. Here, we implement Wheeler's idea along a
satellite-ground interferometer which extends for thousands of kilometers in
Space. We exploit temporal and polarization degrees of freedom of photons
reflected by a fast moving satellite equipped with retro-reflecting mirrors. We
observed the complementary wave-like or particle-like behaviors at the ground
station by choosing the measurement apparatus while the photons are propagating
from the satellite to the ground. Our results confirm quantum mechanical
predictions, demonstrating the need of the dual wave-particle interpretation,
at this unprecedented scale. Our work paves the way for novel applications of
quantum mechanics in Space links involving multiple photon degrees of freedom.Comment: 4 figure
Postselection-loophole-free Bell violation with genuine time-bin entanglement
Entanglement is an invaluable resource for fundamental tests of physics and
the implementation of quantum information protocols such as device-independent
secure communications. In particular, time-bin entanglement is widely exploited
to reach these purposes both in free-space and optical fiber propagation, due
to the robustness and simplicity of its implementation. However, all existing
realizations of time-bin entanglement suffer from an intrinsic postselection
loophole, which undermines their usefulness. Here, we report the first
experimental violation of Bell's inequality with "genuine" time-bin
entanglement, free of the postselection loophole. We introduced a novel
function of the interferometers at the two measurement stations, that operate
as fast synchronized optical switches. This scheme allowed to obtain a
postselection-loophole-free Bell violation of more than nine standard
deviations. Since our scheme is fully implementable using standard fiber-based
components and is compatible with modern integrated photonics, our results pave
the way for the distribution of genuine time-bin entanglement over long
distances.Comment: RevTe
Social farming as an innovative approach to promote mental health, social inclusion and community engagement
I fattori contestuali astratti basati sulla natura vengono riconosciuti come fondamentali per la prevenzione e la promozione della salute mentale . Le aree rurali, infatti, sono sempre più riconosciute come luogo elettivo per la promozione della salute mentale. Negli ultimi anni c'è stata un'ondata di modelli di governance ibrida con base rurale in cui enti pubblici, comunità locali e attori economici uniscono le forze per creare soluzioni di welfare innovative per facilitare le sfide finanziarie (e organizzative) affrontate dai sistemi sanitari nazionali. Utilizzando risorse agricole, come animali e piante, l'agricoltura sociale è in grado di soddisfare esigenze sociali specifiche, tra cui riabilitazione, occupazione protetta, istruzione permanentee altre attività che contribuiscono all'inclusione sociale. Allo stesso tempo, l'agricoltura sociale è in grado di rafforzare la redditività economica e sociale delle comunità rurali. Abbiamo studiato i fattori alla base delle potenzialità delle fattorie sociali per fornire programmi di inserimento lavorativo e riabilitazione per le persone con disturbi mentali. Utilizzando nuove metodologie e strumenti adeguati, abbiamo raccolto dati che indicano gli effetti positivi delle attività agricole sul funzionamento sociale dell'individuo, nonché l'impatto del networking delle aziende agricole sulla sostenibilità del sistema
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