368 research outputs found
Bell Measurements and Observables
A general matrix approach to study entangled states is presented, based on
operator completeness relations. Bases of unitary operators are considered,
with focus on irreducible representations of groups. Bell measurements for
teleportation are considered, and robustness of teleportation to various kinds
of non idealities is shown.Comment: 11 pages. Elsart styl
Quantum teleportation of a single-photon wave packet
A quantum teleportation scheme based on the EPR-pair entangled with respect
to the ``energy+time'' variables is proposed. Teleportation of the multimode
state of a single-photon wave packet is considered.Comment: 6 pages, no figure
Non-local properties of a symmetric two-qubit system
Non-local properties of symmetric two-qubit states are quantified in terms of
a complete set of entanglement invariants. We prove that negative values of
some of the invariants are signatures of quantum entanglement. This leads us to
identify sufficient conditions for non-separability in terms of entanglement
invariants. Non-local properties of two-qubit states extracted from (i) Dicke
state (ii) state generated by one-axis twisting Hamiltonian, and (iii)
one-dimensional Ising chain with nearest neighbour interaction are analyzed in
terms of the invariants characterizing them.Comment: 5 pages, no figure
Cell Biological Markers in Breast Tumours: Applications in cyto- and histopathology
Breast cancer is the most common malignant tumour among women in the
western world, affecting 8-12 % of the female population. In the Netherlands,
breast cancer occurs yearly in IOOO per IOO,OOO women with an absolute
incidence of 9,000 new cases per year. The etiology is multifactorial. Age is
an important risk factor. The incidence climbs after age 30, followed by a slight
dip at menopause and continues to ri se during postmenopausal years.
Honnonal influences are weil documented etiological factors: increasing age of
the mother at birth of her first child increases the risk of breast cancer whereas
late menarche and early menopause decreases the risk. An extensive
collaborative study reanalysing 54 epidemiological studies in 25 countries
provided evidence for a small increase in the relative risk (1.24) of having
breast cancer while taking oral contraceptives and in the IO years after quitting,
with no increased risk IO or more years af ter stopping
Development of the N400 for Word Learning in the First 2 Years of Life: A Systematic Review
The N400 ERP component is a direct neural index of word meaning. Studies show that the N400 component is already present in early infancy, albeit often delayed. Many researchers capitalize on this finding, using the N400 component to better understand how early language acquisition unfolds. However, variability in how researchers quantify the N400 makes it difficult to set clear predictions or build theory. Not much is known about how the N400 component develops in the first 2 years of life in terms of its latency and topographical distributions, nor do we know how task parameters affect its appearance. In the current paper we carry out a systematic review, comparing over 30 studies that report the N400 component as a proxy of semantic processing elicited in infants between 0 and 24 months old who listened to linguistic stimuli. Our main finding is that there is large heterogeneity across semantic-priming studies in reported characteristics of the N400, both with respect to latency and to distributions. With age, the onset of the N400 insignificantly decreases, while its offset slightly increases. We also examined whether the N400 appears different for recently-acquired novel words vs. existing words: both situations reveal heterogeneity across studies. Finally, we inspected whether the N400 was modulated differently with studies using a between-subject design. In infants with more proficient language skills the N400 was more often present or showed itself here with earlier latency, compared to their peers; but no consistent patterns were observed for distribution characteristics of the N400. One limitation of the current review is that we compared studies that widely differed in choice of EEG recordings, pre-processing steps and quantification of the N400, all of which could affect the characteristics of the infant N400. The field is still missing research that systematically tests development of the N400 using the same paradigm across infancy
Continuous variable teleportation of single photon states
The properties of continuous variable teleportation of single photon states
are investigated. The output state is different from the input state due to the
non-maximal entanglement in the EPR beams. The photon statistics of the
teleportation output are determined and the correlation between the field
information beta obtained in the teleportation process and the change in photon
number is discussed. The results of the output photon statistics are applied to
the transmission of a qbit encoded in the polarization of a single photon.Comment: 14 pages, including 6 figure
Quantum secret sharing
Secret sharing is a procedure for splitting a message into several parts so
that no subset of parts is sufficient to read the message, but the entire set
is. We show how this procedure can be implemented using GHZ states. In the
quantum case the presence of an eavesdropper will introduce errors so that his
presence can be detected. We also show how GHZ states can be used to split
quantum information into two parts so that both parts are necessary to
reconstruct the original qubit.Comment: 6 pages, revtex, revised version, to appear in Phys. Rev.
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