50 research outputs found
Experimental Quantum Communication with GNSS satellites
Quantum Communication (QC) is referred as all those protocols that deal with the faithful transportation of quantum states. The huge technological progress in the manipulation of the single quantum particles has led to the experimental tests of some of the most intriguing features of Quantum Mechanics (QM). The gedankenexperiments that were formulated by the fathers of QM in the last century, have become real. In the words of Schrödinger: “... we never experiment with just one electron or atom or (small) molecule.” This is no longer true. We can do experiments involving single atoms or molecules
and even single photons, and thus it becomes possible to demonstrate that the “ridiculous consequences” alluded to by Schrödinger are, in fact, quite real. The possibility of preparing, manipulating and detecting single photons has paved the way for the field of QC . Many interesting applications related to the security of communication start taking shape, of which the most promising is the Quantum Key Distribution ( QKD ). The crucial step towards the establishment of these quantum technologies is the extension of the communication channel up to the possibility of connecting any two points around the
Earth. To this aim, two main strategies are being pursued: the development of quantum repeaters in order to interconnect several fiber-based channels, each of which have limited extension due to the inherent losses of the fiber, and the progress of satellite-to-ground and satellite-to-satellite links that take advantage of the lower losses of the free-space channel. This thesis collects my research under the supervision of Prof. Giuseppe Vallone and Prof. Paolo Villoresi on a set of topics in the quantum communication science, the main objective being the extension of the satellite-to-ground channel towards MEO and its applications on the fundamental tests of QM . Particular attention have also been dedicated to the applications of weak measurements
Rate of complications due to neuromuscular scoliosis spine surgery in a 30-years consecutive series
PURPOSE:
The aim of this study was to evaluate the rate of intraoperative and postoperative complications in a large series of patients affected by neuromuscular scoliosis.
METHODS:
It was a monocentric retrospective study. In this study have been considered complications those events that significantly affected the course of treatment, such as getting the hospital stay longer, or requiring a subsequent surgical procedure, or corrupting the final result of the treatment.
RESULTS:
Of the 358 patients affected by neuromuscular scoliosis treated from January 1985 to December 2010, 185 that met the inclusion criteria were included in the study. There were recorded 66 complications in 55/185 patients. Of that 66 complications, 54 complications occurred in 46/120 patients with Luque's instrumentation, while only 12 complications occurred in 9/65 patients with hybrid instrumentation and this difference was statistically significant (p 0.05).
CONCLUSIONS:
The surgical treatment in neuromuscular scoliosis is burdened by a large number of complications. An accurate knowledge of possible complications is mandatory to prepare strategies due to prevent adverse events. A difference in definitions could completely change results in good or bad as well as in our same series the adverse events amounted at almost 30% of cases, but complications that due to complete failure would amount at 9.19% of patients.
KEYWORDS:
Complications; Neuromuscular scoliosis; Scoliosis; Scoliosis surgery
PMID: 28314995 DOI: 10.1007/s00586-017-5034-6
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Fast and simple qubit-based synchronization for quantum key distribution
We propose Qubit4Sync, a synchronization method for Quantum Key Distribution
(QKD) setups, based on the same qubits exchanged during the protocol and
without requiring additional hardware other than the one necessary to prepare
and measure the quantum states. Our approach introduces a new cross-correlation
algorithm achieving the lowest computational complexity, to our knowledge, for
high channel losses. We tested the robustness of our scheme in a real QKD
implementation
Experimental Demonstration of Sequential Quantum Random Access Codes
A random access code (RAC) is a strategy to encode a message into a shorter
one in a way that any bit of the original can still be recovered with
nontrivial probability. Encoding with quantum bits rather than classical ones
can improve this probability, but has an important limitation: due to the
disturbance caused by standard quantum measurements, qubits cannot be used more
than once. However, as recently shown by Mohan, Tavakoli, and Brunner [New J.
Phys. 21 083034, (2019)], weak measurements can alleviate this problem,
allowing two sequential decoders to perform better than with the best classical
RAC. We use single photons to experimentally show that these weak measurements
are feasible and nonclassical success probabilities are achievable by two
decoders. We prove this for different values of the measurement strength and
use our experimental results to put tight bounds on them, certifying the
accuracy of our setting. This proves the feasibility of using sequential
quantum RACs for quantum information tasks such as the self-testing of
untrusted devices.Comment: See also the related work arXiv:2001.04768 of Hammad Anwer et al.,
appearing on arXiv on the same day of the first submission. V2 includes
changes after peer review and copy-editing. 9 pages, 6 figure
Chest pain caused by multiple exostoses of the ribs: A case report and a review of literature
Abstract
The aim of this paper is to report an exceptional case of
multiple internal exostoses of the ribs in a young patient
affected by multiple hereditary exostoses (MHE) coming
to our observation for chest pain as the only symptom
of an intra-thoracic localization. A 16 years old patient
with familiar history of MHE came to our observation
complaining a left-sided chest pain. This pain had increased
in the last months with no correlation to a
traumatic event. The computed tomography (CT) scan
revealed the presence of three exostoses located on the
left third, fourth and sixth ribs, all protruding into the
thoracic cavity, directly in contact with visceral pleura.
Moreover, the apex of the one located on the sixth rib
revealed to be only 12 mm away from pericardium. Patient
underwent video-assisted thoracoscopy with an additional
4-cm mini toracotomy approach. At the last 1-year followup,
patient was very satisfied and no signs of recurrence or
major complication had occured. In conclusion, chest pain
could be the only symptom of an intra-thoracic exostoses
localization, possibly leading to serious complications.
Thoracic localization in MHE must be suspected when
patients complain chest pain. A chest CT scan is indicated
to confirm exostoses and to clarify relationship with surrounding
structures. Video-assisted thoracoscopic surgery
can be considered a valuable option for exostoses removal,
alone or in addiction to a mini-thoracotomy approach, in
order to reduce thoracotomy morbidity
Direct Reconstruction of the Quantum Density Matrix by Strong Measurements
New techniques based on weak measurements have recently been introduced to
the field of quantum state reconstruction. Some of them allow the direct
measurement of each matrix element of an unknown density operator and need only
different operations, compared to linearly independent projectors
in the case of standard quantum state tomography, for the reconstruction of an
arbitrary mixed state. However, due to the weakness of these couplings, these
protocols are approximated and prone to large statistical errors. We propose a
method which is similar to the weak measurement protocols but works regardless
of the coupling strength: our protocol is not approximated and thus improves
the accuracy and precision of the results with respect to weak measurement
schemes. We experimentally apply it to the polarization state of single photons
and compare the results to those of preexisting methods for different values of
the coupling strength. Our results show that our method outperforms previous
proposals in terms of accuracy and statistical errors.Comment: RevTex, 6 page
Towards Quantum Communication from Global Navigation Satellite System
Satellite-based quantum communication is an invaluable resource for the
realization of a quantum network at the global scale. In this regard, the use
of satellites well beyond the low Earth orbits gives the advantage of long
communication time with a ground station. However, high-orbit satellites pose a
great technological challenge due to the high diffraction losses of the optical
channel, and the experimental investigation of such quantum channels is still
lacking. Here, we report on the first experimental exchange of single photons
from Global Navigation Satellite System at a slant distance of 20000
kilometers, by exploiting the retroreflector array mounted on GLONASS
satellites. We also observed the predicted temporal spread of the reflected
pulses due to the geometrical shape of array. Finally, we estimated the
requirements needed for an active source on a satellite, aiming towards quantum
communication from GNSS with state-of-the-art technology.Comment: Revte
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