403 research outputs found
On the optimality of individual entangling-probe attacks against BB84 quantum key distribution
It is shown that an existing method to study ideal individual attacks on the
BB84 QKD protocol using error discard can be adapted to reconciliation with
error correction, and that an optimal attack can be explicitly found. Moreover,
this attack fills Luetkenhaus bound, independently of whether error positions
are leaked to Eve, proving that it is tight. In addition, we clarify why the
existence of such optimal attacks is not in contradiction with the established
``old-style'' theory of BB84 individual attacks, as incorrectly suggested
recently in a news feature.Comment: 12 pages, 3 figure
Superdeformation and hyperdeformation in the Cd nucleus
The superdeformation and hyperdeformation in Cd have been studied for
the first time within the framework of the fully self-consistent cranked mean
field theory, namely, cranked relativistic mean field theory. The structure of
observed superdeformed bands 1 and 2 have been analyzed in detail. The bumps
seen in their dynamic moments of inertia are explained as arising from unpaired
band crossings. This is contrary to an explanation given earlier within the
framework of projected shell model. It was also concluded that this nucleus is
not doubly magic SD nucleus
Quantum entanglement distribution with 810 nm photons through telecom fibers
We demonstrate the distribution of polarization entangled photons of
wavelength 810 nm through standard telecom fibers. This technique allows
quantum communication protocols to be performed over established fiber
infrastructure, and makes use of the smaller and better performing setups
available around 800 nm, as compared to those which use telecom wavelengths
around 1550 nm. We examine the excitation and subsequent quenching of
higher-order spatial modes in telecom fibers up to 6 km in length, and perform
a distribution of high quality entanglement (visibility 95.6%). Finally, we
demonstrate quantum key distribution using entangled 810 nm photons over a 4.4
km long installed telecom fiber link.Comment: 5 pages, 5 figures, 1 tabl
DESC9115 Lab Report 1
The implementation of the Vibrato and Flanger effect by Oscar GonzalezArchitecture & Allied Art
Universal conductance enhancement and reduction of the two-orbital Kondo effect
We investigate theoretically the linear and nonlinear conductance through a
nanostructure with two-fold degenerate single levels, corresponding to the
transport through nanostructures such as a carbon nanotube, or double dot
systems with capacitive interaction. It is shown that the presence of the
interaction asymmetry between orbits/dots affects significantly the profile of
the linear conductance at finite temperature, and, of the nonlinear
conductance, particularly around half-filling, where the two-particle Kondo
effect occurs. Within the range of experimentally feasible parameters, the
SU(4) universal behavior is suggested, and comparison with relevant experiments
is made.Comment: 10 pages, 16 figure
Notes on the history of brackish water biology at the Universities of Rostock and Greifswald
On the occasion of the celebrations of the 50th year of existence of the biological station at Hiddensee (1982), the 150th jubilee year of the Zoological Institute of the Ernst-Moritz-Arndt-University in Greifswald (1986), and the 25th year of existence of an independent marine biological research and training facility at the University of Rostock (1985), a short overview is given of the development of biological science in the Baltic Sea in the Hither Pomerania and Mecklenburg region. It will become clear that the initiative for brackish water research arose at the University of Greifswald, with algological studies concentrated at Hiddensee and zoological-ecological work in Greifswald itself. Effective and successful marine biological research and teaching at the University of Rostock started with the establishment of the Department of Marine Biology (1960), where university marine biological activities are now concentrated as a result of the university reform (1968)
Hyperdeformation in the cranked relativistic mean field theory: the Z=40-58 part of nuclear chart
The systematic investigation of hyperdeformation (HD) at high spin in the
part of the nuclear chart has been performed in the framework of the
cranked relativistic mean field theory. The properties of the moments of
inertia of the HD bands, the role of the single-particle and necking degrees of
freedom at HD, the spins at which the HD bands become yrast, the possibility to
observe discrete HD bands etc. are discussed in detail.Comment: 22 pages, 25 figure
High-fidelity transmission of entanglement over a high-loss freespace channel
Quantum entanglement enables tasks not possible in classical physics. Many
quantum communication protocols require the distribution of entangled states
between distant parties. Here we experimentally demonstrate the successful
transmission of an entangled photon pair over a 144 km free-space link. The
received entangled states have excellent, noise-limited fidelity, even though
they are exposed to extreme attenuation dominated by turbulent atmospheric
effects. The total channel loss of 64 dB corresponds to the estimated
attenuation regime for a two-photon satellite quantum communication scenario.
We confirm that the received two-photon states are still highly entangled by
violating the CHSH inequality by more than 5 standard deviations. From a
fundamental point of view, our results show that the photons are virtually not
subject to decoherence during their 0.5 ms long flight through air, which is
encouraging for future world-wide quantum communication scenarios.Comment: 5 pages, 3 figures, replaced paper with published version, added
journal referenc
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