158 research outputs found
Directed percolation effects emerging from superadditivity of quantum networks
Entanglement indcued non--additivity of classical communication capacity in
networks consisting of quantum channels is considered. Communication lattices
consisiting of butterfly-type entanglement breaking channels augmented, with
some probability, by identity channels are analyzed. The capacity
superadditivity in the network is manifested in directed correlated bond
percolation which we consider in two flavours: simply directed and randomly
oriented. The obtained percolation properties show that high capacity
information transfer sets in much faster in the regime of superadditive
communication capacity than otherwise possible. As a byproduct, this sheds
light on a new type of entanglement based quantum capacity percolation
phenomenon.Comment: 6 pages, 4 figure
Quantum superadditivity in linear optics networks: sending bits via multiple access Gaussian channels
We study classical capacity regions of quantum Gaussian multiple access
channels (MAC). In classical variants of such channels, whilst some capacity
superadditivity-type effects such as the so called {\it water filling effect}
may be achieved, a fundamental classical additivity law can still be
identified, {\it viz.} adding resources to one sender is never advantageous to
other senders in sending their respective information to the receiver. Here, we
show that quantum resources allows violation of this law, by providing two
illustrative schemes of experimentally feasible Gaussian MACs.Comment: 4 pages, 2 figure
Electro-acoustic transducers on the basis of thin PZT-films
In the present work PZT-type thin films have been obtained by RF sputtering and electroacoustic transducers characterized by high sensitivity (t), wide range of measured relative deformations (q) and high working frequencies (w) were built. Polycrystalline ferroelectric thin films with the perovskite type structure and chemical composition Pb(Zro.33Tio.4sWo.oiCdo.oi)03 have been fabricated by RF sputtering. The films exhibited
slightly lower values of dielectric constant, residual polarization and piezoelectric coefficient </33 = 80 x 10“12 C/N, as compared with the ceramics of the same chemical composition. The thin films keep such a value of du up to the Curie point. On the basis of the PZT-type thin films the isotropic and anisotropic piezoelectric sensors were built and investigated. The electrical signal of the isotropic sensors is proportional to the sum of the
main components of the relative deformation tensor whereas the signal of the anisotropic sensors depends on the angle between the sensor axis and the main axis of the deformation tensor of the sample under investigation. The sensors are characterized by high stability of the generated signal
X-Ray diffraction, mossbauer spectroscopy, and magnetoelectric effect studies of multiferroic Bi5Ti3FeO15 ceramics
Bi5Ti3FeO15 ceramics belongs to multiferroic class of materials. In this work it was prepared by solidstate
sintering method and investigated by X-ray di raction, Mössbauer spectroscopy, and magnetoelectric effect
measurements. As it was proved by X-ray di raction studies the single-phase Bi5Ti3FeO15 compound was
obtained. The Mössbauer investigations revealed paramagnetic character of the compound at room temperature
as well as at 80 K. Magnetoelectric measurements were carried out at room temperature using lock-in
dynamic method and they proved presence of magnetoelectric coupling in this material. Additional magnetoelectric studies were carried out after subsequent electric poling of the sample. It was found that the maximum value of the coupling coe cient was almost twice bigger than in the case without the initial poling and reached a value of ME 20.7 mV cm1 Oe1
Infection control : point prevalence study versus incidence study in Polish long-term care facilities in 2009-2010 in the Małopolska Region
OBJECTIVE: The objective of this study was to evaluate the epidemiology of infection in Polish long-term care facilities (LTCFs) and to analyse the capabilities and legitimacy of implementing continuous targeted surveillance. METHODS: The study investigated the relationship between the presence of infection and health status, tested using a point prevalence study (PPS) and incidence study. A 1-day PPS was carried out in October 2009, with prospective continuous surveillance between December 2009 and November 2010. Infections were defined according to McGeer’s criteria. RESULTS: The surveillance encompassed 193 people. The prevalence was 14.0 % in residential homes (RHs) and 18.7 % in the nursing home (NH). Various types of infections (in the PPS) were observed significantly more frequently in patients with asthma, wounds, atherosclerosis of lower extremities, tracheotomy tubes and conditions in patients hospitalised in intensive care units (ICUs) up to 1 year before the PPS day. The incidence rate was 2.7/1,000 patient days (pds). CONCLUSIONS: The factors determined to be important for the risk of infection (in the continuous study) include the general status of patients, expressed using Barthel, abbreviated mental and Katz scales, as well as limited physical activity, stool incontinence and urinary catheterisation. In the PPS study, only a slight relationship was shown between the general status of residents and the risk of infection. None of the general status scales used clinically were shown to be helpful in estimating that risk, similarly to the five-point physical activity scale. Prospective continuous surveillance shows a possibility of limiting the range of infection control in the LTCFs within targeted surveillance in a population of patients that requires intensive nursing procedures. As a marker, one could point to the low score in the Barthel or Katz scales or low physical activity/bedridden persons
On structural physical approximations and entanglement breaking maps
Very recently a conjecture saying that the so-called structural physical
approximations (SPAa) to optimal positive maps (optimal entanglement witnesses)
give entanglement breaking (EB) maps (separable states) has been posed [J. K.
Korbicz {\it et al.}, Phys. Rev. A {\bf 78}, 062105 (2008)]. The main purpose
of this contribution is to explore this subject. First, we extend the set of
entanglement witnesses (EWs) supporting the conjecture. Then, we ask if SPAs
constructed from other than the depolarizing channel maps also lead to EB maps
and show that in general this is not the case. On the other hand, we prove an
interesting fact that for any positive map there exists an EB channel
such that the SPA of constructed with the aid of is
again an EB channel. Finally, we ask similar questions in the case of
continuous variable systems. We provide a simple way of construction of SPA and
prove that in the case of the transposition map it gives EB channel.Comment: 22 pages, improved version, accepted by Journal of Physics
Nonadditivity effects in classical capacities of quantum multiple-access channels
We study classical capacities of quantum multi-access channels in geometric
terms revealing breaking of additivity of Holevo-like capacity. This effect is
purely quantum since, as one points out, any classical multi-access channels
have their regions additive. The observed non-additivity in quantum version
presented here seems to be the first effect of this type with no additional
resources like side classical or quantum information (or entanglement)
involved. The simplicity of quantum channels involved resembles butterfly
effect in case of classical channel with two senders and two receivers.Comment: 5 pages, 5 figure
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