337 research outputs found
Quantum Communication Protocol Employing Weak Measurements
We propose a communication protocol exploiting correlations between two
events with a definite time-ordering: a) the outcome of a {\em weak
measurement} on a spin, and b) the outcome of a subsequent ordinary measurement
on the spin. In our protocol, Alice, first generates a "code" by performing
weak measurements on a sample of N spins.
The sample is sent to Bob, who later performs a post-selection by measuring
the spin along either of two certain directions. The results of the
post-selection define the "key', which he then broadcasts publicly. Using both
her previously generated code and this key, Alice is able to infer the {\em
direction} chosen by Bob in the post-selection. Alternatively, if Alice
broadcasts publicly her code, Bob is able to infer from the code and the key
the direction chosen by Alice for her weak measurement. Two possible
experimental realizations of the protocols are briefly mentioned.Comment: 5 pages, Revtex, 1 figure. A second protocol is added, where by a
similar set of weak measurement Alice can send, instead of receiving, a
message to Bob. The security question for the latter protocol is discusse
Investment under ambiguity with the best and worst in mind
Recent literature on optimal investment has stressed the difference between the impact of risk and the impact of ambiguity - also called Knightian uncertainty - on investors' decisions. In this paper, we show that a decision maker's attitude towards ambiguity is similarly crucial for investment decisions. We capture the investor's individual ambiguity attitude by applying alpha-MEU preferences to a standard investment problem. We show that the presence of ambiguity often leads to an increase in the subjective project value, and entrepreneurs are more eager to invest. Thereby, our investment model helps to explain differences in investment behavior in situations which are objectively identical
Influence of the detector's temperature on the quantum Zeno effect
In this paper we study the quantum Zeno effect using the irreversible model
of the measurement. The detector is modeled as a harmonic oscillator
interacting with the environment. The oscillator is subjected to the force,
proportional to the energy of the measured system. We use the Lindblad-type
master equation to model the interaction with the environment. The influence of
the detector's temperature on the quantum Zeno effect is obtained. It is shown
that the quantum Zeno effect becomes stronger (the jump probability decreases)
when the detector's temperature increases
Full quantum solutions to the resonant four-wave mixing of two single-photon wave packets
We analyze both analytically and numerically the resonant four-wave mixing of
two co-propagating single-photon wave packets. We present analytic expressions
for the two-photon wave function and show that soliton-type quantum solutions
exist which display a shape-preserving oscillatory exchange of excitations
between the modes. Potential applications including quantum information
processing are discussed.Comment: 7 pages, 3 figure
Qubit Disentanglement and Decoherence via Dephasing
We consider whether quantum coherence in the form of mutual entanglement
between a pair of qubits is susceptible to decay that may be more rapid than
the decay of the coherence of either qubit individually. An instance of
potential importance for solid state quantum computing arises if embedded
qubits (spins, quantum dots, Cooper pair boxes, etc.) are exposed to global and
local noise at the same time. Here we allow separate phase-noisy channels to
affect local and non-local measures of system coherence. We find that the time
for decay of the qubit entanglement can be significantly shorter than the time
for local dephasing of the individual qubits.Comment: REVTeX, 9 pages, 1 figure, v2 with minor changes, reference adde
Establishing the Ethiopian obstetric surveillance system for monitoring maternal outcomes in Eastern Ethiopia: a pilot study
Background: Although the majority of maternal deaths and com-plications occur in low-resource settings, almost all existing strong registration and confidential enquiry systems are found in high -resource settings. We developed and piloted the Ethiopian Obstetric Surveillance System (EthOSS), based on the successful United Kingdom Obstetric Surveillance System (UKOSS) method-ology, in 3 regions in Ethiopia to improve ongoing surveillance and tracking of maternal morbidities and deaths, as well as con-fidential enquiry, compared to the currently used maternal death surveillance and response program in Ethiopia. Methods: We launched the EthOSS monthly case notification sys-tem in 13 hospitals in eastern Ethiopia in April 2021. Study participants included women admitted to the hospitals from April to September 2021 with major adverse obstetric condi-tions during pregnancy, childbirth, or within 42 days of termina-tion of pregnancy. Designated clinicians at the hospitals used a simple online system to report the number of cases and maternal deaths monthly to the EthOSS team. We present findings on the incidence and case fatality rates for adverse conditions included in the EthOSS. Results: Over the 6-month pilot period, 904 women with at least 1 EthOSS condition were included in the study, of whom 10 died (case fatality rate, 1.1%). Almost half (46.6%, 421/904) sus-tained major obstetric hemorrhage, 38.7% (350/904) severe anemia, 29.5% (267/904) eclampsia, 8.8% (80/904) sepsis, and 2.2% (20/904) uterine rupture. To enable care improvement alongside surveillance, the local committee received training on confidential enquiry into maternal deaths from internal and exter-nal experts. Conclusions: In this facility-based project, data on severe ad-verse obstetric conditions were captured through voluntary reporting by clinicians. Further analysis is essential to assess the robustness of these data, and confidential enquiry into maternal deaths for specific cases is planned to investigate the appropri-ateness of care
Nucleation of a sodium droplet on C60
We investigate theoretically the progressive coating of C60 by several sodium
atoms. Density functional calculations using a nonlocal functional are
performed for NaC60 and Na2C60 in various configurations. These data are used
to construct an empirical atomistic model in order to treat larger sizes in a
statistical and dynamical context. Fluctuating charges are incorporated to
account for charge transfer between sodium and carbon atoms. By performing
systematic global optimization in the size range 1<=n<=30, we find that Na_nC60
is homogeneously coated at small sizes, and that a growing droplet is formed
above n=>8. The separate effects of single ionization and thermalization are
also considered, as well as the changes due to a strong external electric
field. The present results are discussed in the light of various experimental
data.Comment: 17 pages, 10 figure
FGF receptor genes and breast cancer susceptibility: results from the Breast Cancer Association Consortium
Background:Breast cancer is one of the most common malignancies in women. Genome-wide association studies have identified FGFR2 as a breast cancer susceptibility gene. Common variation in other fibroblast growth factor (FGF) receptors might also modify risk. We tested this hypothesis by studying genotyped single-nucleotide polymorphisms (SNPs) and imputed SNPs in FGFR1, FGFR3, FGFR4 and FGFRL1 in the Breast Cancer Association Consortium.
Methods:Data were combined from 49 studies, including 53 835 cases and 50 156 controls, of which 89 050 (46 450 cases and 42 600 controls) were of European ancestry, 12 893 (6269 cases and 6624 controls) of Asian and 2048 (1116 cases and 932 controls) of African ancestry. Associations with risk of breast cancer, overall and by disease sub-type, were assessed using unconditional logistic regression.
Results:Little evidence of association with breast cancer risk was observed for SNPs in the FGF receptor genes. The strongest evidence in European women was for rs743682 in FGFR3; the estimated per-allele odds ratio was 1.05 (95 confidence interval=1.02-1.09, P=0.0020), which is substantially lower than that observed for SNPs in FGFR2.
Conclusion:Our results suggest that common variants in the other FGF receptors are not associated with risk of breast cancer to the degree observed for FGFR2. © 2014 Cancer Research UK
Measurement of and charged current inclusive cross sections and their ratio with the T2K off-axis near detector
We report a measurement of cross section and the first measurements of the cross section
and their ratio
at (anti-)neutrino energies below 1.5
GeV. We determine the single momentum bin cross section measurements, averaged
over the T2K -flux, for the detector target material (mainly
Carbon, Oxygen, Hydrogen and Copper) with phase space restricted laboratory
frame kinematics of 500 MeV/c. The
results are and $\sigma(\nu)=\left( 2.41\
\pm0.022{\rm{(stat.)}}\pm0.231{\rm (syst.)}\ \right)\times10^{-39}^{2}R\left(\frac{\sigma(\bar{\nu})}{\sigma(\nu)}\right)=
0.373\pm0.012{\rm (stat.)}\pm0.015{\rm (syst.)}$.Comment: 18 pages, 8 figure
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