82 research outputs found
Modalités d'interaction avec des systèmes d'aide à la décision médicale par alerte ou à la demande pour délivrer des recommandations : une étude préliminaire dans le cadre de la prise en charge de l'hypertension
Classiquement développés comme des systèmes d'alertes produisant automatiquement des thérapeutiques centrées patient, les systèmes d'aide à la décision médicale sont appréciés par les médecins utilisateurs de façon variable selon les études. Nous pensons que ce mode d'interaction n'est pertinent que dans les cas simples où le médecin pense a priori qu'il n'a pas besoin d'être aidé. Une approche " à la demande " nous semble, par ailleurs, adaptée dans les cas plus compliqués. Nous avons testé cette hypothèse avec le système ASTI développé de façon à proposer deux modes d'interaction. Dédié aux cas simples, le mode " critique ", entièrement automatique, produit des alertes lorsque la prescription médicamenteuse du médecin n'est pas conforme aux recommandations. Au contraire, le mode " guidé " est utilisé de façon volontaire par le médecin qui, au cours d'une navigation active au sein d'une base de connaissances, accède dans les cas complexes aux recommandations thérapeutiques. Un score de complexité des cas cliniques a été proposé. Une étude préliminaire a été conduite sur 15 cas cliniques et 10 généralistes qui valide notre hypothèse de travail
High resolution spectroscopy of single NV defects coupled with nearby C nuclear spins in diamond
We report a systematic study of the hyperfine interaction between the
electron spin of a single nitrogen-vacancy (NV) defect in diamond and nearby
C nuclear spins, by using pulsed electron spin resonance spectroscopy.
We isolate a set of discrete values of the hyperfine coupling strength ranging
from 14 MHz to 400 kHz and corresponding to C nuclear spins placed at
different lattice sites of the diamond matrix. For each lattice site, the
hyperfine interaction is further investigated through nuclear spin polarization
measurements and by studying the magnetic field dependence of the hyperfine
splitting. This work provides informations that are relevant for the
development of nuclear-spin based quantum register in diamond.Comment: 8 pages, 5 figure
Electron spin resonance detected by a superconducting qubit
A new method for detecting the magnetic resonance of electronic spins at low
temperature is demonstrated. It consists in measuring the signal emitted by the
spins with a superconducting qubit that acts as a single-microwave-photon
detector, resulting in an enhanced sensitivity. We implement this new type of
electron-spin resonance spectroscopy using a hybrid quantum circuit in which a
transmon qubit is coupled to a spin ensemble consisting of NV centers in
diamond. With this setup we measure the NV center absorption spectrum at 30mK
at an excitation level of \thicksim15\,\mu_{B} out of an ensemble of 10^{11}
spins.Comment: 6 pages, 4 figures, submitted to PR
Engineered arrays of NV color centers in diamond based on implantation of CN- molecules through nanoapertures
We report a versatile method to engineer arrays of nitrogen-vacancy (NV)
color centers in dia- mond at the nanoscale. The defects were produced in
parallel by ion implantation through 80 nm diameter apertures patterned using
electron beam lithography in a PMMA layer deposited on a diamond surface. The
implantation was performed with CN- molecules which increased the NV defect
formation yield. This method could enable the realization of a solid-state
coupled-spin array and could be used for positioning an optically active NV
center on a photonic microstructure.Comment: 12 pages, 3 figure
Free induction decay of single spins in diamond
We study both theoretically and experimentally the free induction decay (FID)
of the electron spin associated with a single nitrogen-vacancy defect in high
purity diamond, where the main source of decoherence is the hyperfine
interaction with a bath of C nuclear spins. In particular, we report a
systematic study of the FID signal as a function of the strength of a magnetic
field oriented along the symmetry axis of the defect. On average, an increment
of the coherence time by a factor of is observed at high magnetic
field in diamond samples with a natural abundance of C nuclear spins, in
agreement with numerical simulations and theoretical studies. Further
theoretical analysis shows that this enhancement is independent of the
concentration of nuclear spin impurities. By dividing the nuclear spin bath
into shells and cones, we theoretically identify which nuclear spins are
responsible for the observed dynamics.Comment: 16 pages, 7 figure
Composite-pulse magnetometry with a solid-state quantum sensor
The sensitivity of quantum magnetometers is challenged by control errors and,
especially in the solid-state, by their short coherence times. Refocusing
techniques can overcome these limitations and improve the sensitivity to
periodic fields, but they come at the cost of reduced bandwidth and cannot be
applied to sense static (DC) or aperiodic fields. Here we experimentally
demonstrate that continuous driving of the sensor spin by a composite pulse
known as rotary-echo (RE) yields a flexible magnetometry scheme, mitigating
both driving power imperfections and decoherence. A suitable choice of RE
parameters compensates for different scenarios of noise strength and origin.
The method can be applied to nanoscale sensing in variable environments or to
realize noise spectroscopy. In a room-temperature implementation based on a
single electronic spin in diamond, composite-pulse magnetometry provides a
tunable trade-off between sensitivities in the microT/sqrt(Hz) range,
comparable to those obtained with Ramsey spectroscopy, and coherence times
approaching T1
Hybrid quantum circuit with a superconducting qubit coupled to a spin ensemble
We report the experimental realization of a hybrid quantum circuit combining
a superconducting qubit and an ensemble of electronic spins. The qubit, of the
transmon type, is coherently coupled to the spin ensemble consisting of
nitrogen-vacancy (NV) centers in a diamond crystal via a frequency-tunable
superconducting resonator acting as a quantum bus. Using this circuit, we
prepare arbitrary superpositions of the qubit states that we store into
collective excitations of the spin ensemble and retrieve back later on into the
qubit. These results constitute a first proof of concept of spin-ensemble based
quantum memory for superconducting qubits.Comment: 13 pages, 4 figures, plus supplementary informatio
Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
For more than 80 years, the counterintuitive predictions of quantum theory
have stimulated debate about the nature of reality. In his seminal work, John
Bell proved that no theory of nature that obeys locality and realism can
reproduce all the predictions of quantum theory. Bell showed that in any local
realist theory the correlations between distant measurements satisfy an
inequality and, moreover, that this inequality can be violated according to
quantum theory. This provided a recipe for experimental tests of the
fundamental principles underlying the laws of nature. In the past decades,
numerous ingenious Bell inequality tests have been reported. However, because
of experimental limitations, all experiments to date required additional
assumptions to obtain a contradiction with local realism, resulting in
loopholes. Here we report on a Bell experiment that is free of any such
additional assumption and thus directly tests the principles underlying Bell's
inequality. We employ an event-ready scheme that enables the generation of
high-fidelity entanglement between distant electron spins. Efficient spin
readout avoids the fair sampling assumption (detection loophole), while the use
of fast random basis selection and readout combined with a spatial separation
of 1.3 km ensure the required locality conditions. We perform 245 trials
testing the CHSH-Bell inequality and find . A
null hypothesis test yields a probability of that a local-realist
model for space-like separated sites produces data with a violation at least as
large as observed, even when allowing for memory in the devices. This result
rules out large classes of local realist theories, and paves the way for
implementing device-independent quantum-secure communication and randomness
certification.Comment: Raw data will be made available after publicatio
Haplotype tagging reveals parallel formation of hybrid races in two butterfly species.
Genetic variation segregates as linked sets of variants or haplotypes. Haplotypes and linkage are central to genetics and underpin virtually all genetic and selection analysis. Yet, genomic data often omit haplotype information due to constraints in sequencing technologies. Here, we present "haplotagging," a simple, low-cost linked-read sequencing technique that allows sequencing of hundreds of individuals while retaining linkage information. We apply haplotagging to construct megabase-size haplotypes for over 600 individual butterflies (Heliconius erato and H. melpomene), which form overlapping hybrid zones across an elevational gradient in Ecuador. Haplotagging identifies loci controlling distinctive high- and lowland wing color patterns. Divergent haplotypes are found at the same major loci in both species, while chromosome rearrangements show no parallelism. Remarkably, in both species, the geographic clines for the major wing-pattern loci are displaced by 18 km, leading to the rise of a novel hybrid morph in the center of the hybrid zone. We propose that shared warning signaling (Müllerian mimicry) may couple the cline shifts seen in both species and facilitate the parallel coemergence of a novel hybrid morph in both comimetic species. Our results show the power of efficient haplotyping methods when combined with large-scale sequencing data from natural populations
A computer decision aid for medical prevention: a pilot qualitative study of the Personalized Estimate of Risks (EsPeR) system
BACKGROUND: Many preventable diseases such as ischemic heart diseases and breast cancer prevail at a large scale in the general population. Computerized decision support systems are one of the solutions for improving the quality of prevention strategies. METHODS: The system called EsPeR (Personalised Estimate of Risks) combines calculation of several risks with computerisation of guidelines (cardiovascular prevention, screening for breast cancer, colorectal cancer, uterine cervix cancer, and prostate cancer, diagnosis of depression and suicide risk). We present a qualitative evaluation of its ergonomics, as well as it's understanding and acceptance by a group of general practitioners. We organised four focus groups each including 6–11 general practitioners. Physicians worked on several structured clinical scenari os with the help of EsPeR, and three senior investigators leaded structured discussion sessions. RESULTS: The initial sessions identified several ergonomic flaws of the system that were easily corrected. Both clinical scenarios and discussion sessions identified several problems related to the insufficient comprehension (expression of risks, definition of familial history of disease), and difficulty for the physicians to accept some of the recommendations. CONCLUSION: Educational, socio-professional and organisational components (i.e. time constraints for training and use of the EsPeR system during consultation) as well as acceptance of evidence-based decision-making should be taken into account before launching computerised decision support systems, or their application in randomised trials
- …