83,150 research outputs found
Quantification of entanglement via uncertainties
We show that entanglement of pure multi-party states can be quantified by
means of quantum uncertainties of certain basic observables through the use of
measure that has been initially proposed in [10] for bipartite systems.Comment: Changed content, references added 7 pages, no figures, PRA in pres
Steady state entanglement of two atoms created by classical driving field
The stabilization of steady state entanglement caused by action of a
classical driving field in the system of two-level atoms with the dipole
interaction accompanied by spontaneous emission is discussed. An exact solution
shows that the maximum amount of concurrence that can be achieved in Lamb-Dicke
limit is 0.43, which corresponds to the entanglement
ebit. Dependence of entanglement on interatomic distance and classical driving
field is examined numerically.Comment: 14 pages, 2 figure
Path integral representation of the evolution operator for the Dirac equation
A path integral representation of the evolution operator for the
four-dimensional Dirac equation is proposed. A quadratic form of the canonical
momenta regularizes the original representation of the path integral in the
electron phase space. This regularization allows to obtain a representation of
the path integral over trajectories in the configuration space, i.e. in the
Minkowsky space. This form of the path integral is useful for the formulation
of perturbation theory in an external electromagnetic field.Comment: 3 page
Refining structures against reflection rank: an alternative metric for electron crystallography.
A new metric is proposed to improve the fidelity of structures refined against precession electron diffraction data. The inherent dynamical nature of electron diffraction ensures that direct refinement of recorded intensities against structure-factor amplitudes can be prone to systematic errors. Here it is shown that the relative intensity of precessed reflections, their rank, can be used as an alternative metric for refinement. Experimental data from erbium pyrogermanate show that applying precession reduces the dynamical transfer of intensity between reflections and hence stabilizes their rank, enabling accurate and reliable structural refinements. This approach is then applied successfully to an unknown structure of an oxygen-deficient bismuth manganite resulting in a refined structural model that is similar to a calcium analogue.The authors thank the EPSRC for financial support through grant number HO1771
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