The European Physical Journal D最新文献

We perform a systematic study of the electron momentum distribution symmetry properties in electron–atom scattering assisted by an orthogonally polarized two-color laser field. We show that the dynamical symmetry of the field is imprinted onto the electron momentum distribution. In addition to the direct electron scattering off the atom, which we call the single scattering, we consider the case of rescattering where the laser field-driven electron returns and rescatters off the atom. We pay a particular attention to the role of the relative phase between the laser field components. In the single-scattering case, we identify additional symmetry properties arising from the laser field configuration. Furthermore, using the stationary phase method we derived energy conservation conditions, both for single scattering and for the rescattering. With the aid of these conditions, we assess the position of the cutoff electron energy and investigate its dependence of the laser field parameters. Our results demonstrate that the laser field parameters allow independent control of the single-scattering and rescattering plateaus. For some configurations, the rescattering plateau extends to significantly higher energies than for the single scattering.

Electron momentum distributions in the final momentum plane for (a,b) linearly polarized, (c,d) (omega )–(2omega ), and (e,f) (2omega )–(omega ) OTC fields with equal component intensities and relative phase (phi = 0^circ ). Initial energies: (E_{text {i}} = 0) eV (a,c,e) and 10 eV (b,d,f)

We propose a scheme to enhance quantum entanglement in an optomechanical system consisting of two mechanically coupled mechanical resonators, which are driven by a common electromagnetic field. Each mechanical resonator is linearly and quadratically coupled to the electromagnetic field. Moreover, the mechanical coupling between the resonators is modulated through a given phase that allows interference control in our structure. By tuning this phase, our system exhibits interference like-structure which is reminiscent of bright and dark mode features. The breaking of the dark mode via the phase adjustment leads to an entanglement generation, which is greatly enhanced through the quadratic coupling. Furthermore, the generated entanglement is robust enough against thermal noise and this resilience is improved when the quadratic coupling is accounted. Our work provides a way to enhance quantum entanglement via quadratic coupling which is assisted by interference control. Such quantum resources can be useful for quantum information processing, quantum computing, and other numerous quantum tasks.

Nonlinear Langmuir oscillations in a cold bounded plasma of finite resistivity have been analyzed. Without recourse to the Lagrangian coordinates, a class of exact space-time-dependent solution of the governing 1D Euler–Poisson equations has been obtained. Under well-defined boundary and initial conditions, a piecewise linear solution of the equations on a segment is constructed. The method outlined here for solving the equations is expected to be fruitfully applied in many branches of nonlinear physics having similar model.

Spatio-temporal evolution of electron fluid velocity

In their seminal paper, Einstein, Podolsky, and Rosen (EPR) had introduced a momentum-entangled state for two particles. That state, referred to as the EPR state, has been widely used in studies on entangled particles with continuous degrees of freedom. Later that state was generalized to a form that allows varying degree of entanglement, known as the generalized EPR state. In a suitable limit it reduces to the EPR state. The generalized EPR state is theoretically analyzed here and its entanglement quantified in terms of a recently introduced generalized entanglement measure. This state can also be applied to entangled photons produced from spontaneous parametric down-conversion (SPDC). The present analysis is then used in quantifying the entanglement of photons produced from the SPDC process, in terms of certain experimental parameters. A comparison is also made with the Schmidt number, which is normally used as an entanglement measure in such situations. A procedure for experimentally determining the entanglement of SPDC photons has also been described. Furthermore, an additional state exhibiting non-Gaussian entanglement has been examined, and its entanglement has been quantified.

While laser excitation of the nuclear isomeric transition in (^{229})Th has been recently achieved for thorium atoms embedded in large-bandgap crystals, laser excitation and characterization of the nuclear transition in trapped (^{229})Th(^{3+}) ions has not yet been accomplished. To address these experiments, a cryogenic Paul trap setup has been designed, built, and commissioned at LMU Munich. Here, we present the specifications of the new experimental platform and demonstrate its successful operation, showing the extraction, subsequent ion guiding, mass purification, and trapping of (^{229})Th(^{3+}) and (^{229text {m}})Th(^{3+}) ions from a newly designed buffer-gas stopping cell as well as of (^{88})Sr(^{+}) ions from laser ablation of a solid target. Further, we show sympathetic laser cooling of (^{229text {(m)}})Th(^{3+}) by Doppler-cooled (^{88})Sr(^{+}) ions and the formation of mixed-species Coulomb crystals.