In the analysis of quantum discord, the minimization of average entropy traditionally involved over orthogonal projective measurements may be attained at more optimal decompositions by using the positive-operator-valued measure（POVM）measurements. Taking advantage of the quantum steering ellipsoid in combination with three-element POVM optimization,we show that, for a family of two-qubit X states locally interacting with Markovian non-dissipative environments, the decay rates of quantum discord show smooth dynamical evolutions without any sudden change. This is in contrast to two-element orthogonal projective measurements, in which case the sudden change of the decay rates of quantum and classical decoherences may be a common phenomenon. Notwithstanding this, we find that a subset of X states（including the Bell diagonal states） involving POVM optimization can still preserve the sudden change character as usual.
From a classical dynamic simulation,we find the kinetic energy of the electrons generated during laser plasma generation depends on the laser polarization and intensity.The electron kinetic energy reaches its maximum with a fixed laser intensity for circularly polarized laser pulse.The fluorescence spectra at 380.4 nm from N2 and 391.3 nm from N2^＋ are measured;these are generated by both the direct excitation and electron collision excitation.The electron collision excitation is determined by the electron energy and reaches the maximal with a circularly polarized pulse.
We theoretically investigate high-order harmonic generation in a two-color multi-cycle inhomogeneous field combined with a 27th harmonic pulse. By considering a bowtie-shaped gold nanostructure, the spatiotemporal profiles of enhanced plasmonic fields are obtained by solving the Maxwell equation using finite-domain time-difference method. Based on quantum-mechanical and classical models, the effect of 27th harmonic pulse, temporal profile of enhanced plasmonic field and inhomogeneity on supercontinuum generation are analyzed and discussed. As a result, broadband supercontinuum can be generated from our approach with optimized gap size of nanostructure. Moreover, these results are not sensitively dependent on the relative phase in the two-color field.
We investigate the nonadiabatic spectral redshift of high-order harmonic of He driven by two time-delayed orthogonally polarized laser fields. It is found that the nonadiabatic spectral redshift can be observed by properly adjusting the time delay of the two laser fields when the controlling pulse is added in the raising part of the driving pulse in the vertical direction. That is because the controlling pulse in the vertical direction prevents the ionized electrons from returning to the vicinity of parent ions and then reduces the recombination probability. This leads to the high-order harmonic generated mainly in the falling part of the driving pulse. Meanwhile,we also find that the quantity of redshift can be effectively controlled through accommodating the positive time delays. In addition, this scheme can also be used to produce nonadiabatic spectral blueshift.
Hongmei WuShengjun YueJinbin LiSilin FuBitao HuHongchuan Du
Dear Editors,Energy exchange between two filamentary pulses was demonstrated in several experiments [ 1-4], and the energy- transfer direction depends on the time delay between filamen- tary pulses, the initial chirp, the laser intensities, the location, the crossing angle and the relative polarization. However, the understanding of the physical mechanisms of energy ex- change in literatures are different and puzzling, including the impulsive Raman nonlinear response of the molecules [1], the plasma-mediated forward stimulated Raman scattering [2], the traveling plasma grating [3], and the classical two beam coupling model [4].
