164 research outputs found
Study and Design of a Control System for generating and detecting Qubits for the Quantum Exchange of Cryptographic Key
We realized a system for quantum information exchange for cryptographic applications. VHDL describes the hardware for lasers driving and data reception; C++ implements the software for system management. The design is integrated on two boards. A synchronization method guarantees the right timing of the system. The unpredictably of qubit transmission is handled by a suitable time-calibrated receiving windows system. Achieved results improve previous system version in performaces and reliability.ope
An Appraisal of Muon Neutrino Disappearance at Short Baseline
Neutrino physics is nowadays receiving more and more attention as a possible
source of information for the long standing problem of new Physics beyond the
Standard Model. The recent measurements of the third mixing angle
in the standard mixing oscillation scenario encourage to pursue the still
missing results on the leptonic CP violation and the absolute neutrino masses.
However, several puzzling and incomplete measurements are in place which
deserve an exhaustive evaluation and study. We will report about the present
situation of the muon disappearance measurements at small in the context
of the current CERN project to revitalize the neutrino field in Europe and the
search for sterile neutrinos. We will then illustrate the achievements that a
double muon spectrometer can attain in terms of discovery of new neutrino
states, performing a newly developed analysis.Comment: 19 pages, 8 figures, to be published in "Advances in High Energy
Physics
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
Stable, low-error and calibration-free polarization encoder for free-space quantum communication
Polarization-encoded free-space Quantum Communication requires a quantum
state source featuring fast polarization modulation, long-term stability and a
low intrinsic error rate. Here we present a source based on a Sagnac
interferometer and composed of polarization maintaining fibers, a fiber
polarization beam splitter and an electro-optic phase modulator. The system
generates predetermined polarization states with a fixed reference frame in
free-space that does not require calibration neither at the transmitter nor at
the receiver. In this way we achieve long-term stability and low error rates. A
proof-of-concept experiment is also reported, demonstrating a Quantum Bit Error
Rate lower than 0.2% for several hours without any active recalibration of the
devices.Comment: 6 pages, 2 figure
All-fiber self-compensating polarization encoder for Quantum Key Distribution
Quantum Key Distribution (QKD) allows distant parties to exchange
cryptographic keys with unconditional security by encoding information on the
degrees of freedom of photons. Polarization encoding has been extensively used
in QKD implementations along free-space, optical fiber and satellite-based
links. However, the polarization encoders used in such implementations are
unstable, expensive, complex and can even exhibit side-channels that undermine
the security of the implemented protocol. Here we propose a self-compensating
polarization encoder based on a Lithium Niobate phase modulator inside a Sagnac
interferometer and implement it using only standard telecommunication
commercial off-the-shelves components (COTS). Our polarization encoder combines
a simple design and high stability reaching an intrinsic quantum bit error rate
as low as 0.2%. Since realization is possible from the 800 nm to the 1550 nm
band by using COTS, our polarization modulator is a promising solution for
free-space, fiber and satellite-based QKD.Comment: REVTeX, 5 pages, 4 figure
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
Simple Quantum Key Distribution with qubit-based synchronization and a self-compensating polarization encoder
Quantum Key Distribution (QKD) relies on quantum communication to allow
distant parties to share a secure cryptographic key. Widespread adoption of QKD
in current telecommunication networks will require the development of simple,
low cost and stable systems. However, current QKD implementations usually
include additional hardware that perform auxiliary tasks such as temporal
synchronization and polarization basis tracking. Here we present a
polarization-based QKD system operating at 1550 nm that performs
synchronization and polarization compensation by exploiting only the hardware
already needed for the quantum communication task. Polarization encoding is
performed by a self-compensating Sagnac loop modulator which exhibits high
temporal stability and the lowest intrinsic quantum bit error rate reported so
far.The QKD system was tested over a fiber-optic link, demonstrating tolerance
up to about 40 dB of channel losses. Thanks to its reduced hardware
requirements and the quality of the source, this work represents an important
step towards technologically mature QKD systems.Comment: 8 pages, 4 figure
Resource-effective Quantum Key Distribution: a field-trial in Padua city center
Field-trials are of key importance for novel technologies seeking
commercialization and wide-spread adoption. This is certainly also the case for
Quantum Key Distribution (QKD), which allows distant parties to distill a
secret key with unconditional security. Typically, QKD demonstrations over
urban infrastructures require complex stabilization and synchronization systems
to maintain a low Quantum Bit Error (QBER) and high secret key rates over time.
Here we present a field-trial which exploits a low-complexity self-stabilized
hardware and a novel synchronization technique, to perform QKD over optical
fibers deployed in the city center of Padua, Italy. In particular, two
techniques recently introduced by our research group are evaluated in a
real-world environment: the iPOGNAC polarization encoder was used for the
preparation of the quantum states, while the temporal synchronization was
performed using the Qubit4Sync algorithm. The results here presented
demonstrate the validity and robustness of our resource-effective QKD system,
that can be easily and rapidly installed in an existing telecommunication
infrastructure, thus representing an important step towards mature, efficient
and low-cost QKD systems.Comment: 5 pages, 3 figure
European Strategy for Accelerator-Based Neutrino Physics
Massive neutrinos reveal physics beyond the Standard Model, which could have
deep consequences for our understanding of the Universe. Their study should
therefore receive the highest level of priority in the European Strategy. The
discovery and study of leptonic CP violation and precision studies of the
transitions between neutrino flavours require high intensity, high precision,
long baseline accelerator neutrino experiments. The community of European
neutrino physicists involved in oscillation experiments is strong enough to
support a major neutrino long baseline project in Europe, and has an ambitious,
competitive and coherent vision to propose. Following the 2006 European
Strategy for Particle Physics (ESPP) recommendations, two complementary design
studies have been carried out: LAGUNA/LBNO, focused on deep underground
detector sites, and EUROnu, focused on high intensity neutrino facilities.
LAGUNA LBNO recommends, as first step, a conventional neutrino beam CN2PY from
a CERN SPS North Area Neutrino Facility (NANF) aimed at the Pyhasalmi mine in
Finland. A sterile neutrino search experiment which could also be situated in
the CERN north area has been proposed (ICARUS-NESSIE) using a two detector
set-up, allowing a definitive answer to the 20 year old question open by the
LSND experiment. EUROnu concluded that a 10 GeV Neutrino Factory, aimed at a
magnetized neutrino detector situated, also, at a baseline of around 2200 km
(+-30%), would constitute the ultimate neutrino facility; it recommends that
the next 5 years be devoted to the R&D, preparatory experiments and
implementation study, in view of a proposal before the next ESPP update. The
coherence and quality of this program calls for the continuation of neutrino
beams at CERN after the CNGS, and for a high priority support from CERN and the
member states to the experiments and R&D program.Comment: Prepared by the program committee of the Neutrino `town meeting',
CERN, 14-16 May 2012 and submitted to the European Strategy For European
Particle Physic
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