2,729 research outputs found
Multipartite quantum correlation and entanglement in four-qubit pure states
Based on the quantitative complementarity relations, we analyze thoroughly
the properties of multipartite quantum correlations and entanglement in
four-qubit pure states. We find that, unlike the three-qubit case, the single
residual correlation, the genuine three- and four-qubit correlations are not
suited to quantify entanglement. More interestingly, from our qualitative and
numerical analysis, it is conjectured that the sum of all the residual
correlations may constitute a good measure for the total multipartite
entanglement in the system.Comment: 7 pages, 3 figue
Bridged [2.2.1] bicyclic phosphine oxide facilitates catalytic γ-umpolung addition-Wittig olefination.
A novel bridged [2.2.1] bicyclic phosphine oxide, devised to circumvent the waste generation and burdens of purification that are typical of reactions driven by the generation of phosphine oxides, has been prepared in three steps from commercially available cyclopent-3-ene-1-carboxylic acid. The performance of this novel phosphine oxide was superior to those of current best-in-class counterparts, as verified experimentally through kinetic analysis of its silane-mediated reduction. It has been applied successfully in halide-/base-free catalytic γ-umpolung addition-Wittig olefinations of allenoates and 2-amidobenzaldehydes to produce 1,2-dihydroquinolines with good efficiency. One of the 1,2-dihydroquinoline products was converted to known antitubercular furanoquinolines
Self-current induced spin-orbit torque in FeMn/Pt multilayers
Extensive efforts have been devoted to the study of spin-orbit torque in
ferromagnetic metal/heavy metal bilayers and exploitation of it for
magnetization switching using an in-plane current. As the spin-orbit torque is
inversely proportional to the thickness of the ferromagnetic layer, sizable
effect has only been realized in bilayers with an ultrathin ferromagnetic
layer. Here we demonstrate that, by stacking ultrathin Pt and FeMn alternately,
both ferromagnetic properties and current induced spin-orbit torque can be
achieved in FeMn/Pt multilayers without any constraint on its total thickness.
The critical behavior of these multilayers follows closely three-dimensional
Heisenberg model with a finite Curie temperature distribution. The spin torque
effective field is about 4 times larger than that of NiFe/Pt bilayer with a
same equivalent NiFe thickness. The self-current generated spin torque is able
to switch the magnetization reversibly without the need for an external field
or a thick heavy metal layer. The removal of both thickness constraint and
necessity of using an adjacent heavy metal layer opens new possibilities for
exploiting spin-orbit torque for practical applications.Comment: 28 pages, 5 figure
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