562 research outputs found
Cyclic nonlinear interferometry with entangled non-Gaussian spin states
We propose an efficient nonlinear readout scheme for entangled non-Gaussian
spin states (ENGSs) based on the intrinsic quasi-cyclic dynamics of interacting
spin-1/2 systems. We focus on two well-known spin models of twist-and-turn
(TNT) and two-axis-counter-twisting (TACT), where ENGS can be generated by spin
dynamics starting from unstable fixed points. In the TNT model, non-Gaussian
probe state evolves directly back to the vicinity of initial state during the
subsequent time-forward evolution for path recombining, accompanied by quantum
magnification of encoded signal and refocusing of the associated quantum noise.
Based on low-order moment measurement, we find the optimal metrological gain
nearly saturates the quantum Cramer-Rao bound (QCRB) and follows the Heisenberg
scaling. For the TACT case, the QCRB can also be nearly approached when the
state converges to either of the two unstable fixed points, respectively
corresponding to the initial state or its orthogonal coherent state. The latter
case goes beyond previous studies where tracing back to or crossing the initial
states is mostly considered. The present protocol does not require
time-reversal as in typical nonlinear interferometries, and it also avoids
complicated measurement of nonlinear observables or full probability
distributions. The operational approach we discuss presents a practical way for
realizing high-precision and detection-noise-robust quantum metrology with
ENGS.Comment: 10 pages, 6 figure
4,6-Dimethyl-2-(naphthalen-1-yl)pyrimidine
The asymmetric unit of the title compound, C16H14N2, contains two independent molecules in which the dihedral angles between the pyrimidine and naphthaline rings are 38.20 (5) and 39.35 (5)°. Intermolecular C—H⋯π contacts and π–π stacking interactions [centroid–centroid distances = 3.766 (1) and 3.792 (1) Å] are present in the crystal structure
Immunoglobulin G4-related disease complicated with vascular lesions: CT findings in 21 patients
PURPOSE:We aimed to analyze multislice computed tomography (MSCT) imaging features of vasculitis in immunoglobulin G4-related disease (IgG4-RD).METHODS:In this retrospective study, we diagnosed 21 definite or possible IgG4-RD patients (71.4% male; mean age, 52.1±4.5 years) with vasculitis by MSCT and pathologic examination. The clinical background, laboratory analysis, pathologic results, CT images, and response to therapy were assessed and analyzed.RESULTS:Under enhanced MSCT, 50 vasculitic lesions were identified and were divided into five types (types A–E) according to the CT findings on the basis of luminal changes. There were more vasculitic lesions observed below the diaphragm (n=30) than above it (n=20). Aneurysms and aneurysmal dilatation were more likely to be found in the aortaventralis (n=5), aortic arch (n=3) and iliac arteries (n=3). Most of the vascular lesions were characterized by wall thickening with a normal lumen (n=15) and slight stenosis (n=22). The affected vascular walls were all thickened between 4 and 18 mm. The walls of 19 patients (90.4%) were well circumscribed. The wall thickness of the aorta, including the aortaventralis and aortic arch, was more notable than that of the other vascular sites. Fourteen patients were followed up for 2–24 months. Wall thickness decreased in all cases. The average maximum thicknesses before and after therapy were 12.2±2.7 mm and 6.1±1.8 mm, which were significantly different (P < 0.001). The lumens of two patients were found to be slightly enlarged, while those of the other cases were unchanged after therapy.CONCLUSION:IgG4-RD vascular lesions can be divided into five types, which are more likely to be present in the aorta and its main branches, and can rapidly diminish after steroid therapy. The lumen may be unchanged or slightly enlarged
Error-Disturbance Trade-off in Sequential Quantum Measurements
We derive a state dependent error-disturbance trade-off based on a
statistical distance in the sequential measurements of a pair of noncommutative
observables and experimentally verify the relation with a photonic qubit
system. We anticipate that this Letter may further stimulate the study on the
quantum uncertainty principle and related applications in quantum measurements
Superconductivity with up to 30.7 K in air-annealed CaFeAsF
Exploring new unconventional superconductors is of great value for both
fundamental research and practical applications. It is a long-term challenge to
develop and study more hole-doped superconductors in 1111 system of iron-based
superconductors. However, fifteen years after the discovery of iron-based
superconductors, it has become increasingly difficult to discover new members
in this system by conventional means. Here we report the discovery of
superconductivity with the critical transition temperature up to 30.7 K in the
parent compound CaFeAsF by an annealing treatment in air atmosphere. The
superconducting behaviors are verified in both the single-crystalline and
polycrystalline samples by the resistance and magnetization measurements. The
analysis by combining the depth-resolved time-of-flight secondary ion mass
spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) measurements
show that the introduction of oxygen elements and the consequent changing in Fe
valence by the annealing treatment may lead to the hole-type doping, which is
the origin for the occurrence of superconductivity. Our results provide a new
route to induce hole-doped superconductivity in Fe-based superconductors.Comment: 20 pages, 4 figures and 1 tabl
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