209 research outputs found
Extremal Quantum Correlations: Experimental Study with Two-qubit States
We explore experimentally the space of two-qubit quantum correlated mixed
states, including frontier ones as defined by the use of quantum discord and
von Neumann entropy. Our experimental setup is flexible enough to allow for the
high-quality generation of a vast variety of states. We address quantitatively
the relation between quantum discord and a recently suggested alternative
measure of quantum correlations.Comment: 5 pages, 2 figure
Experimental Realization of the Deutsch-Jozsa Algorithm with a Six-Qubit Cluster State
We describe the first experimental realization of the Deutsch-Jozsa quantum
algorithm to evaluate the properties of a 2-bit boolean function in the
framework of one-way quantum computation. For this purpose a novel two-photon
six-qubit cluster state was engineered. Its peculiar topological structure is
the basis of the original measurement pattern allowing the algorithm
realization. The good agreement of the experimental results with the
theoretical predictions, obtained at 1kHz success rate, demonstrate the
correct implementation of the algorithm.Comment: 5 pages, 2 figures, RevTe
Phase control of a longitudinal momentum entangled photon state by a deformable membrane mirror
We propose a paradigmatic demonstration of the potentialities of a deformable
mirror for closed-loop control of a two-photon momentum-entangled state,
subject to phase fluctuations. A custom-made membrane mirror is used to set a
relative phase shift between the arms of an interferometric apparatus. The
control algorithm estimates the phase of the quantum state, by measurements of
the coincidence events at the output ports of the interferometer, and uses the
measurements results to provide a feedback signal to the deformable mirror.
Stabilization of the coincidence rate to within 1.5 standard deviation of the
Poissonian noise is demonstrated over 2000 seconds.Comment: RevTex, 6 page
Multi-path entanglement of two photons
We present a novel optical device based on an integrated system of
micro-lenses and single mode optical fibers. It allows to collect and direct
into many modes two photons generated by spontaneous parametric down
conversion. By this device multiqubit entangled states and/or multilevel
qu-it states of two photons, encoded in the longitudinal momentum degree of
freedom, are created. The multi-path photon entanglement realized by this
device is expected to find important applications in modern quantum information
technology.Comment: 4 pages, 3 figures, revtex, revised versio
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
Two-particle bosonic-fermionic quantum walk via 3D integrated photonics
Quantum walk represents one of the most promising resources for the
simulation of physical quantum systems, and has also emerged as an alternative
to the standard circuit model for quantum computing. Up to now the experimental
implementations have been restricted to single particle quantum walk, while
very recently the quantum walks of two identical photons have been reported.
Here, for the first time, we investigate how the particle statistics, either
bosonic or fermionic, influences a two-particle discrete quantum walk. Such
experiment has been realized by adopting two-photon entangled states and
integrated photonic circuits. The polarization entanglement was exploited to
simulate the bunching-antibunching feature of non interacting bosons and
fermions. To this scope a novel three-dimensional geometry for the waveguide
circuit is introduced, which allows accurate polarization independent
behaviour, maintaining a remarkable control on both phase and balancement.Comment: 4 pages, 5 figures + supplementary informatio
Impact of turbulence in long range quantum and classical communications
The study of the free-space distribution of quantum correlations is necessary
for any future application of quantum as classical communication aiming to
connect two remote locations. Here we study the propagation of a coherent laser
beam over 143 Km (between Tenerife and La Palma Islands of the Canary
archipelagos). By attenuating the beam we also studied the propagation at the
single photon level. We investigated the statistic of arrival of the incoming
photons and the scintillation of the beam. From the analysis of the data, we
propose the exploitation of turbulence to improve the SNR of the signal.Comment: 5 Pages, 5 figures, 1 Table, revtex
Adsorption of Methane in Porous Materials as the Basis for the Storage of Natural Gas
It is well known that the natural gas (NG) is a substance of fossil origin from the decomposition of organic matter. It is found trapped under the terrestrial surface in stratus that avoid the natural release to atmosphere. These underground deposits can be oceanic or terrestrial. The NG is a homogeneous mixture, having variable proportions of hydrocarbons, being the main constitute the methane (CH4), which content generally ranges from 55 to 98 % in volume. Also, it contains ethane (C2H6), propane (C3H8) and heavier constitutes. Although it can be found in gas phase or in solution with oil, under normal atmospheric conditions, remains in gas phase. It may have some impurities or substances that are not hydrocarbons, such as Hydrogen Sulfide, Nitrogen and Carbon Dioxide (Figure 1). According to its origin, natural gas is classified in associated and non-associated, being the first, the one which remains in contact and/or dissolved with the oil from the deposit. The non-associated gas can be found in deposits lacking oil crude at the initial conditions of pressure and temperature.Fil: Solar, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Garcia Blanco, Andres Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Vallone, Andrea Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; Argentin
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
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