62 research outputs found
Broadening the bandwidth of entangled photons: a step towards the generation of extremely short biphotons
We demonstrate a technique that allows to fully control the bandwidth of
entangled photons independently of the frequency band of interest and of the
nonlinear crystal. We show that this technique allows to generate nearly
transform-limited biphotons with almost one octave of bandwidth (hundreds of
THz) which corresponds to correlation times of just a few femtoseconds. The
presented method becomes an enabling tool for attosecond entangled-photons
quantum optics. The technique can also be used to generate paired photons with
a very high degree of entanglement.Comment: 4 page
Entanglement of coherent states and decoherence
A possibility to produce entangled superpositions of strong coherent states
is discussed. A recent proposal by Howell and Yazell [Phys. Rev. A 62, 012102
(2000)] of a device which entangles two strong coherent coherent states is
critically examined. A serious flaw in their design is found. New modified
scheme is proposed and it is shown that it really can generate non-classical
states that can violate Bell inequality. Moreover, a profound analysis of the
effect of losses and decoherence on the degree of entanglement is accomplished.
It reveals the high sensitivity of the device to any disturbances and the
fragility of generated states
Generation of polarization-entangled photon pairs in a Bragg reflection waveguide
We demonstrate experimentally that spontaneous parametric down-conversion in
an AlGaAs semiconductor Bragg reflection waveguide can make for paired photons
highly entangled in the polarization degree of freedom at the telecommunication
wavelength of 1550 nm. The pairs of photons show visibility higher than 90% in
several polarization bases and violate a Clauser-Horne-Shimony-Holt Bell-like
inequality by more than 3 standard deviations. This represents a significant
step toward the realization of efficient and versatile self pumped sources of
entangled photon pairs on-chip.Comment: 9 pages, 4 figures, published versio
Типовая учебная программа по учебной дисциплине для специальности: 1-23 01 08 Журналистика (по направлениям), направление специальности 1-23 01 08-02 Журналистика (аудиовизуальная)
Enhancement of soft magnetic properties in the selected group of amorphous alloys was examined by different
experimental methods. It was shown that permeability for annealed samples (at Ta for 1 h; 300 K < Ta < 900 K)
plotted vs. Ta shows a maximum at which is 700, 725, 725, and 750 K for Fe82Nb2B14Y2, Fe82Nb2B14Gd2,
Fe82Nb2B14Tb2 and Fe82Nb2B14Dy2 alloy, respectively. For samples after the optimization annealing permeability
is at least 10 times higher than in the as-quenched state. The optimized microstructure is free of iron nanograins
and corresponds to so-called relaxed amorphous phase
Experimental estimation of the dimension of classical and quantum systems
An overwhelming majority of experiments in classical and quantum physics make
a priori assumptions about the dimension of the system under consideration.
However, would it be possible to assess the dimension of a completely unknown
system only from the results of measurements performed on it, without any extra
assumption? The concept of a dimension witness answers this question, as it
allows one to bound the dimension of an unknown classical or quantum system in
a device-independent manner, that is, only from the statistics of measurements
performed on it. Here, we report on the experimental demonstration of dimension
witnesses in a prepare and measure scenario. We use pairs of photons entangled
in both polarization and orbital angular momentum to generate ensembles of
classical and quantum states of dimensions up to 4. We then use a dimension
witness to certify their dimensionality as well as their quantum nature. Our
results open new avenues for the device-independent estimation of unknown
quantum systems and for applications in quantum information science.Comment: See also similar, independent and jointly submitted work of J. Ahrens
et al., quant-ph/1111.127
Entanglement transformation at absorbing and amplifying four-port devices
Dielectric four-port devices play an important role in optical quantum
information processing. Since for causality reasons the permittivity is a
complex function of frequency, dielectrics are typical examples of noisy
quantum channels, which cannot preserve quantum coherence. To study the effects
of quantum decoherence, we start from the quantized electromagnetic field in an
arbitrary Kramers--Kronig dielectric of given complex permittivity and
construct the transformation relating the output quantum state to the input
quantum state, without placing restrictions on the frequency. We apply the
formalism to some typical examples in quantum communication. In particular we
show that for entangled qubits the Bell-basis states are more
robust against decoherence than the states .Comment: 12 pages, revtex, 10 eps figures, minor corrections in Appendi
The cycle and effect of zinc in the blast-furnace process
This article analyzes the eff ect of zinc in the blast furnace process and it also analysis its contents in the input and
output raw materials. The results obtained in the long-term research project will be used as data here. The removal
of zinc from the input raw materials is very diffi cult already in the sinter production stage. This is due to its uniform
distribution in the raw materials, but also due to the fact that it does not transfer into gas phase during the sintering
process. The content of Zinc compounds was experimentally measured in the lining. The quan ty of penetrated Zinc
is diff erent in diff erent parts of the blast furnace. As demonstrated by the research, zinc repeatedly enters the blast
furnace process, which leads to its circula on.Web of Science52220019
Surface magnetic properties and domains observation in as-quenched and annealed FeNbB ribbons
The longitudinal magneto-optical Kerr effect (MOKE) combined with the magneto-optical microscopy is used to investigate the surface magnetic anisotropy and the domain behavior in as-quenched (AQ) and strain-annealed (SA) FeNbB ribbons. X-ray diffraction, conversion electron Mössbauer spectroscopy (CEMS), and scanning electron microscopy (SEM) confirmed the existence of approximately View the MathML source thick magnetically harder layer on the ribbon air side, consisting of crystallites embedded in an amorphous matrix. The underneath bulk phase is amorphous and magnetically soft. Residual anisotropies and the domain patterns (wide in-plane domains with 180ring operator walls and narrow fingerprint domains) corresponding to amorphous phase are mainly caused by the internal stresses originating from the rapid quenching process. In the surface crystalline phase they are gradually overlapped by strip domains with magnetization directions almost perpendicular to the ribbon axis. The anisotropy changes caused by additional annealing and straining of the samples are shown and discussed in detail
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