Search results for "Polar"
showing 10 items of 3817 documents
Nonperturbative treatments of nonresonant multiphoton ionization of the hydrogen atom: weak-field limit
1989
A nonperturbative treatment of the multiphoton ionization of the hydrogen atom based on the S matrix and devised for nonresonant strong-field situations is analyzed in the weak-field limit. Comparisons are presented with other S matrices as well as other nonperturbative approaches. Our treatment is found to perform generally better than similar S-matrix treatments. The usual perturbative results are recovered provided that the photon wavelengths are sufficiently short and are off resonance with the atomic transitions. Important indications are obtained as to the role of the atomic structure, the relevance of the gauge consistency, and the reliability and improvement of the present nonpertur…
Experimental quantum entanglement and teleportation by tuning remote spatial indistinguishability of independent photons.
2020
Quantitative control of spatial indistinguishability of identical subsystems as a direct quantum resource at distant sites has not yet been experimentally proven. We design a setup capable of tuning remote spatial indistinguishability of two independent photons by individually adjusting their spatial distribution in two distant regions, leading to polarization entanglement from uncorrelated photons. This is achieved by spatially localized operations and classical communication on photons that meet only at the detectors. The amount of entanglement depends uniquely on the degree of spatial indistinguishability, quantified by an entropic measure I , which enables teleportation with fidelities …
Suppression of the frequency drifts in polarization modulational instability spectra by means of a photon reservoir
2012
By appropriately combining the effects of second- and fourth-order dispersion, and by carefully choosing the pump power, we create a photon reservoir which suppresses the drifts of sidebands in the spectra of polarization modulational instability
Unrestricted generation of pure two-qubit states and entanglement diagnosis by single-qubit tomography.
2019
We present an experimental proof-of-principle for the generation and detection of pure two-qubit states that have been encoded in degrees of freedom that are common to both classical-light beams and single photons. Our protocol requires performing polarization tomography on a single qubit from a qubit pair. The degree of entanglement in the qubit pair is measured by concurrence, which can be directly extracted from intensity measurements-or photon counting-entering single-qubit polarization tomography.
Polarization Effects in Photo- and Electrodisintegration of the Deuteron
1986
Polarization observables in deuteron photodisintegration like photon and target asymmetries and one- and two nucleon polarization of the final state are studied with respect to their sensitivity to subnuclear degrees of freedom. Furthermore it is shown that the electric form factor of the neutron has a sizeable influence on the polarization asymmetry in d(\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}}{e}\),e’n)p with polarized electrons. Uncertainties arising from potential model dependence are discussed.
Control of multiphoton radiative recombination through the action of two low-frequency fields
2004
Interference effects caused by the simultaneous action of a two low frequency fields with commensurate frequencies during laser assisted radiative recombination (LARR) are investigated theoretically. Varying the relative phase of the two fields the following LARR features may be controlled: a) location of the maxima in the total emitted power; b) enhancement of the total emitted power; c) polar shape of the differential emitted power; d) shape of the emitted power spectra.
Spin and Orbital Magnetic Moments of FePt Thin Films
2006
The magnetic moments of disordered and ordered L10 Fe50Pt50 films were investigated using magnetic circular dichroism (MCD) and spin polarized full relativistic Korringa–Kohn–Rostoker (SPRKKR) calculations. The measurements showed that the spin magnetic moments of Fe in both ordered and disordered films were similar with a lower value than that obtained by SPRKKR calculations. Both films however showed larger orbital moments of Fe compared to the calculations. It is suggested that the spin magnetic moment of Fe in FePt thin films was insensitive to L10 ordering.
Spin Currents injected electrically and thermally from highly spin polarized Co$_2$MnSi
2015
We demonstrate the injection and detection of electrically and thermally generated spin currents probed in Co$_2$MnSi/Cu lateral spin valves. Devices with different electrode separations are patterned to measure the non-local signal as a function of the electrode spacing and we determine a relatively high effective spin polarization $\alpha$ of Co$_2$MnSi to be 0.63 and the spin diffusion length of Cu to be 500 nm at room temperature. The electrically generated non-local signal is measured as a function of temperature and a maximum signal is observed for a temperature of 80 K. The thermally generated non-local signal is measured as a function of current density and temperature in a second h…
Controlling stability and transport of magnetic microswimmers by an external field
2019
We investigate the hydrodynamic stability and transport of magnetic microswimmers in an external field using a kinetic theory framework. Combining linear stability analysis and nonlinear 3D continuum simulations, we show that for sufficiently large activity and magnetic field strengths, a homogeneous polar steady state is unstable for both puller and pusher swimmers. This instability is caused by the amplification of anisotropic hydrodynamic interactions due to the external alignment and leads to a partial depolarization and a reduction of the average transport speed of the swimmers in the field direction. Notably, at higher field strengths a reentrant hydrodynamic stability emerges where t…
Polarity and bioelectrical patterning in a linear chain of non-excitable cells
2020
Abstract Polarity in multicellular systems is influenced by bioelectrical signals because electric potentials can act as spatio-temporal patterns for other biochemical processes that eventually emerge as long-lasting biological outcomes. We study the role of the electric potential in establishing head-tail polarity for the case of a chain of non-excitable cells. This biophysical model incorporates both single-cell (membrane ion channels) and multicellular (intercellular gap junctions) characteristics. The results are presented in the form of a bioelectrical phase space that complements traditional biochemical approaches and provides qualitative insights for the case of anterior/posterior po…